DRUG NAME: Levothyroxine

Levothyroxine sodium (L-thyroxine, T4) is the marketed salt form. A synthetic levo-isomer of thyroxine, identical to the endogenous thyroid hormone T4 produced by the thyroid gland. The name Levothyroxine is used throughout this monograph. International originator brand: Synthroid (AbbVie, US); in India, the originator brand was Eltroxin (GlaxoSmithKline, subsequently Mylan/Viatris).

Therapeutic Class: Thyroid Hormone

Subclass: Synthetic Thyroxine (T4)

Speciality:

Primary Speciality: Endocrinology
Also used in: Obstetrics & Gynaecology, Paediatrics, Oncology (thyroid cancer management)

Schedule (India): Schedule H

Route(s)

Oral (tablets — primary route), IV (for myxedema coma — limited availability in India)

Biosimilar Status:
Not a biologic — biosimilar classification not applicable. Levothyroxine is a small-molecule synthetic hormone. However, ℹ️ narrow therapeutic index (NTI) drug — bioequivalence between different brands may not guarantee therapeutic equivalence. Brand switching is a clinical concern (see Clinical Pearls).

Formulations Available in India

Dosage Form	Strengths Available	Notes
Tablets	12.5 mcg, 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg	Not all strengths available from all brands. Thyronorm (Abbott) offers widest range.
Soft gel capsules	25 mcg, 50 mcg, 75 mcg, 100 mcg, 125 mcg, 150 mcg	Limited brands in India. Advantage: fewer absorption interactions with food/drugs; more consistent bioavailability.
Oral solution	25 mcg/mL, 50 mcg/mL, 100 mcg/mL	Very limited availability in India. Useful for neonates/infants and patients with swallowing difficulty.
Injection (lyophilised powder)	100 mcg/vial, 200 mcg/vial, 500 mcg/vial	⚠️ Very limited availability in India. Not stocked at most hospitals. Often needs to be sourced from specialty importers or select manufacturers. Critical for myxedema coma but frequently unavailable — see Clinical Pearls for alternative approach.

Clinically Relevant FDCs Available in India:

FDC	Strengths Available	Notes
Levothyroxine + Liothyronine (T4 + T3)	Thyroxine 100 mcg + Liothyronine 20 mcg (and other ratios)	Available from limited brands. ℹ️ NOT routinely recommended. API Textbook, ATA, and Indian Thyroid Society consensus recommend levothyroxine monotherapy for hypothyroidism. T4+T3 combination has no proven superiority over T4 alone for symptom relief in adequately powered trials. Use only under endocrinologist supervision for refractory symptoms despite euthyroid biochemistry on T4 monotherapy.

⛔ Banned FDCs: No levothyroxine-containing FDC has been specifically banned by CDSCO gazette notification as of this writing. However, irrational FDCs combining thyroid hormones with vitamins, minerals, or unrelated drugs should not be prescribed.

PHARMACOKINETICS

Parameter	Value
Bioavailability (oral)	40–80% (highly variable). Fasting absorption: ~70–80%. ⚠️ Food reduces absorption by 20–40%. Must be taken on an empty stomach at least 30–60 minutes before food for optimal and consistent absorption. Soft gel capsules may have slightly better absorption consistency with food but empty-stomach dosing is still preferred.
Tmax	2–4 hours
Protein binding	>99.97% — bound to thyroxine-binding globulin (TBG, ~75%), thyroxine-binding prealbumin (transthyretin, TBPA, ~15%), and albumin (~10%). Only the unbound (free) fraction (~0.03%) is biologically active.
Volume of distribution (Vd)	~10–12 L (small Vd reflecting very high protein binding; distributes primarily in extracellular space initially, then enters intracellular compartment)
Metabolism	Peripheral deiodination is the primary metabolic pathway: Type I and II 5’-deiodinase convert T4 → T3 (active form, ~80% of circulating T3 comes from peripheral conversion). Type III 5-deiodinase converts T4 → reverse T3 (rT3, inactive). Also undergoes hepatic conjugation (glucuronidation, sulfation) with enterohepatic recycling. No significant CYP-mediated metabolism. Not a significant substrate, inhibitor, or inducer of CYP enzymes. Drug transporters: Substrate of MCT8 (monocarboxylate transporter 8), OATP1C1, and other thyroid hormone transporters. Clinical drug transporter interactions are not a major concern at the prescribing level.
Half-life (t½)	6–7 days in euthyroid patients. 9–10 days in hypothyroid patients (reduced clearance). 3–4 days in hyperthyroid patients (increased clearance). ℹ️ This very long half-life means: (a) steady state takes 4–6 weeks to achieve, (b) TSH should be rechecked no sooner than 4–6 weeks after any dose change, © a single missed dose has minimal clinical impact.
Excretion	~20–40% faecal (conjugated metabolites via bile, some enterohepatic recycling). ~40–60% renal (as deaminated and conjugated metabolites). Minimal unchanged drug in urine.
Dialysability	Not significantly removed by haemodialysis or peritoneal dialysis (>99.97% protein bound). No supplemental post-dialysis dose needed.
Food effect	⚠️ CRITICAL: Food significantly reduces absorption (20–40% reduction). Coffee (including decaf), milk, soy milk, fibre, papaya, and grapefruit juice also reduce absorption. Must be taken with water only, on an empty stomach, at least 30–60 minutes before breakfast. This is the single most important counselling point for levothyroxine.
Onset of action	Biochemical: TSH begins to fall within 3–5 days. Clinical symptomatic improvement: 2–3 weeks. Full clinical and biochemical euthyroid state: 4–6 weeks.
Duration of action	Due to long half-life (6–7 days), once-daily dosing provides stable circulating T4/T3 levels. Effect persists for 1–3 weeks after discontinuation.

Non-linear PK: Not clinically significant. Absorption is roughly proportional to dose at standard therapeutic doses. At very high doses (>300 mcg), absorption may be proportionally lower.

Enterohepatic Recycling: ~20% of T4 undergoes enterohepatic recycling. Drugs that bind bile acids (cholestyramine, colestipol) or alter gut flora can reduce this recycling and lower effective T4 levels.

Population PK Notes

Population	PK Difference
Elderly	Decreased T4 clearance (reduced peripheral deiodination). Lower dose requirement. TSH reference range may be higher in elderly (especially >70 years).
Pregnancy	⚠️ Increased T4 requirement by 25–50% due to: increased TBG levels (oestrogen effect), expanded volume of distribution, increased renal clearance, placental deiodination (Type III deiodinase in placenta converts T4 → rT3). Dose increase must be implemented early (by week 4–6).
Renal impairment	Minimal effect — levothyroxine is not significantly renally cleared. No dose adjustment for renal impairment per se, but CKD patients may have altered protein binding and thyroid hormone metabolism.
Hepatic impairment	Severe liver disease may reduce T4 → T3 conversion and alter TBG levels. Clinical significance is usually minor. No standard dose adjustment.
Obesity	Higher lean body weight → higher T4 requirement. Dosing based on ideal body weight (IBW) is more appropriate than actual body weight in obese patients, though adjustments are made based on TSH.
Paediatric	Infants and young children have higher T4 requirements per kg compared to adults (higher metabolic rate, higher T4 clearance). See Paediatric Dosing.
Critical illness (ICU)	“Sick euthyroid syndrome” (non-thyroidal illness syndrome) — low T3, low/normal T4, normal/low TSH. ⚠️ Do NOT routinely treat with levothyroxine unless true hypothyroidism is confirmed. Sick euthyroid is an adaptive response to illness and normalises with recovery. Treating it with thyroid hormone can be harmful.

ADULT INDICATIONS + DOSING

Primary Indications (Approved / Standard in India)

1. Primary Hypothyroidism (Overt)

This is the most common indication — represents >95% of levothyroxine prescriptions in India.

Patient Group	Starting Dose	Titration	Usual Maintenance Dose	Maximum Dose (per dose / per day)
Young, healthy adults (<60 years, no cardiac disease)	1.6 mcg/kg/day (full replacement dose can be started directly) OR 50–100 mcg/day	Check TSH at 4–6 weeks. Adjust by 12.5–25 mcg increments.	75–150 mcg/day (average ~100–125 mcg/day)	200 mcg per dose; 300 mcg per day (doses >200 mcg are rare and require investigation for malabsorption, non-compliance, or drug interactions)
Elderly (≥60 years) or cardiac disease	⚠️ 12.5–25 mcg/day	Increase by 12.5–25 mcg every 4–6 weeks until TSH normalises	50–100 mcg/day (often lower requirement)	150 mcg/day (higher doses only with cardiologist input)
Severe/prolonged hypothyroidism (TSH >50, or myxedema features without coma)	12.5–25 mcg/day	Increase by 12.5–25 mcg every 2–4 weeks	Titrate to TSH target	As per general adult maximum
Oral (only route for outpatient management)	As above	As above	As above	As above

Target TSH: 0.5–4.0 mIU/L (general population). Some guidelines use 0.5–2.5 mIU/L as optimal target, but this is debated. Individualise based on patient age, symptoms, and comorbidities.

Mandatory Clinical Notes:

When to prefer over alternatives: Levothyroxine (T4) monotherapy is the universal standard of care for hypothyroidism globally and in India. No alternative is preferred. Liothyronine (T3) monotherapy or T4+T3 combination is NOT routinely recommended (ATA, ETA, API Textbook, Indian Thyroid Society). Desiccated thyroid extract is NOT available or recommended in India. [Evidence-based]
When NOT to use: ⛔ Do not start levothyroxine in a patient with untreated adrenal insufficiency — can precipitate adrenal crisis (T4 increases cortisol metabolism). Always exclude/treat adrenal insufficiency FIRST before starting thyroid replacement, especially in panhypopituitarism. ⛔ Do not start full replacement dose in elderly or cardiac patients — risk of angina, MI, arrhythmia. ⛔ Do not start levothyroxine based on a single borderline TSH — repeat testing to confirm.
NLEM India status: ✅ Yes — Levothyroxine sodium 25 mcg and 50 mcg tablets are included in NLEM India 2022 (listed under Section 18: Hormones and Other Endocrine Medicines).
Time to expected clinical response: Symptomatic improvement begins in 2–3 weeks. Full euthyroid state biochemically: 4–6 weeks. Some symptoms (dry skin, hair loss, weight) may take 3–6 months to fully resolve. ℹ️ Educate patients that this is a slow-acting hormone — do not expect overnight improvement.
Treatment failure criteria: (a) TSH fails to normalise after 8–12 weeks at expected full replacement dose (1.6 mcg/kg/day) → investigate: adherence (most common cause), timing of tablet (taken with food?), drug interactions (calcium, iron, PPI), malabsorption (coeliac disease, atrophic gastritis, post-bariatric surgery), interference with TSH assay (biotin supplements). (b) Persistent symptoms despite normal TSH → re-evaluate: differential diagnosis (depression, anaemia, sleep apnoea, vitamin D deficiency — extremely common in India), patient expectations, trial of dose adjustment to lower TSH within range.
Mandatory baseline investigations:
- MANDATORY: TSH (primary diagnostic test), Free T4 (fT4)
- RECOMMENDED: Anti-TPO antibodies (to confirm autoimmune aetiology — Hashimoto’s thyroiditis); lipid profile (dyslipidaemia common in hypothyroidism); FBC (anaemia screen); vitamin B12, vitamin D (commonly low in Indian patients with hypothyroidism)
- OPTIONAL: Free T3 (not routinely needed — useful only if T3 thyrotoxicosis suspected or in euthyroid sick syndrome); thyroid ultrasound (only if goitre or nodules present — NOT routine for biochemical hypothyroidism)
- MANDATORY (in elderly/cardiac): ECG before starting or increasing dose
Specialist vs primary care: Can be initiated and managed in primary care for uncomplicated primary hypothyroidism. Refer to endocrinologist for: central (secondary/tertiary) hypothyroidism, thyroid cancer TSH suppression, pregnancy-related thyroid disease, treatment-resistant hypothyroidism, myxedema coma, paediatric/neonatal hypothyroidism.
Indian guideline source: API Textbook of Medicine, 11th Edition — Chapter on Thyroid Disorders. Indian Thyroid Society (ITS) Guidelines. Endocrine Society of India recommendations. ICMR guidelines on iodine deficiency disorders.
⚠️ Key disease-specific safety warning: In elderly patients and those with coronary artery disease, starting full-dose levothyroxine can precipitate angina, myocardial infarction, or arrhythmia by increasing myocardial oxygen demand. Always start low (12.5–25 mcg) and go slow in this population.
Dose adjustment scenarios:
- Obesity: Dose based on lean body weight/IBW; obese patients often need ~1.0–1.2 mcg/IBW/day rather than actual weight
- Pregnancy: Increase dose by 25–50% as soon as pregnancy confirmed (see Pregnancy section)
- Post-thyroidectomy or RAI: Full replacement dose usually 1.6–1.8 mcg/kg/day needed immediately
- Drug interactions: May need 25–50% dose increase if starting calcium, iron, PPI, cholestyramine, rifampicin, phenytoin, carbamazepine, oestrogens

2. Subclinical Hypothyroidism (SCH)

ℹ️ This is NOT a universal indication for levothyroxine treatment. Decision to treat depends on TSH level, symptoms, age, comorbidities, and anti-TPO antibody status.

Clinical Scenario	Treatment Decision	Dose
TSH 4.5–10 mIU/L, asymptomatic, anti-TPO negative	Do NOT treat routinely. Repeat TSH in 6–12 months.	Not applicable
TSH 4.5–10 mIU/L, symptomatic (fatigue, weight gain, depression, constipation, dyslipidaemia)	Consider treatment trial for 3–6 months. Reassess symptoms and TSH. If no benefit, consider stopping.	Start 25–50 mcg/day
TSH 4.5–10 mIU/L, anti-TPO positive	Recommend treatment — high likelihood of progression to overt hypothyroidism (4–5% per year conversion rate)	Start 25–50 mcg/day
TSH >10 mIU/L (regardless of symptoms)	Treat — universally recommended	Start 50 mcg/day (25 mcg in elderly/cardiac), titrate to target TSH
Pregnancy or planning pregnancy with TSH >2.5 mIU/L	Treat (see Pregnancy section)	Start 25–50 mcg/day, target TSH <2.5
Children and adolescents with SCH	Refer to paediatric endocrinologist	—

Mandatory Clinical Notes:

When to prefer treatment: TSH >10, anti-TPO positive with TSH 4.5–10, symptomatic with TSH 4.5–10, planning pregnancy, goitre, dyslipidaemia attributable to hypothyroidism.
When NOT to treat: ⚠️ Overdiagnosis and overtreatment of SCH is a major problem in India. A single mildly elevated TSH (e.g., 5.0–6.0 mIU/L) on routine “thyroid profile” screening does NOT warrant immediate lifelong levothyroxine. Repeat TSH in 6–8 weeks before making treatment decisions. TSH varies diurnally (higher in early morning), with illness, and with assay variability. Many patients are unnecessarily started on levothyroxine based on a single borderline result and then find it difficult to stop.
NLEM India status: ✅ Yes (the drug is listed; the indication is managed per clinical judgment).
Time to response: If treating for symptoms — reassess at 3–6 months. If no symptomatic improvement despite normalised TSH, the symptoms likely have another cause.
Treatment failure: Persistent symptoms despite normalised TSH → investigate other causes (depression, anaemia, sleep apnoea, vitamin D deficiency, perimenopause).
Mandatory baseline: TSH (repeated on two occasions 6–8 weeks apart), fT4, anti-TPO antibodies.
Specialist vs primary care: Can be managed in primary care. Specialist referral for uncertain cases, children, elderly >70 years.
Indian guideline source: Indian Thyroid Society position statement on subclinical hypothyroidism. API Textbook. ATA Guidelines (supportive).
Key safety warning: Do NOT treat SCH in elderly >70–80 years with TSH <10 mIU/L — recent landmark trials (TRUST trial, 2017) show no benefit and potential harm (overtreatment → atrial fibrillation, bone loss, angina).
Dose adjustment: Lower starting doses (25 mcg) sufficient for SCH. Target TSH need not be <2.5 mIU/L except in pregnancy.

3. TSH Suppression Therapy — Post-Thyroid Cancer (Differentiated Thyroid Cancer — DTC)

Risk Category	TSH Target	Usual Dose Requirement	Duration
High risk (large tumour, extrathyroidal extension, distant metastases, incomplete structural response)	TSH <0.1 mIU/L (full suppression)	Typically 2.0–2.5 mcg/kg/day (higher than replacement)	Lifelong or until risk reclassification
Intermediate risk (microscopic extrathyroidal extension, aggressive histology, incomplete biochemical response)	TSH 0.1–0.5 mIU/L	1.8–2.2 mcg/kg/day	Re-evaluate at 1–2 years; may reduce suppression if excellent response
Low risk (intrathyroidal, <4 cm, no metastases, excellent response to therapy)	TSH 0.5–2.0 mIU/L (near-normal)	1.6–1.8 mcg/kg/day (standard replacement)	Lifelong replacement but no suppression needed

Mandatory Clinical Notes:

When to prefer: All patients post-total thyroidectomy ± RAI for DTC require levothyroxine — both for hormone replacement AND TSH-dependent tumour growth suppression. [Evidence-based]
When NOT to use aggressive suppression: ⛔ Elderly patients (>65 years), patients with coronary artery disease, atrial fibrillation, osteoporosis — risk of iatrogenic thyrotoxicosis outweighs benefit of suppression. Target near-normal TSH (0.5–2.0) in these patients regardless of tumour risk.
NLEM India status: ✅ Yes.
Time to response: TSH suppression achieved in 4–6 weeks. Adjust dose based on TSH levels.
Treatment failure: TSH fails to suppress despite high doses → investigate adherence, absorption issues. Consider thyroglobulin levels for disease monitoring.
Mandatory baseline: TSH, fT4, fT3, thyroglobulin (Tg), anti-Tg antibodies, calcium/PTH (post-thyroidectomy hypoparathyroidism), neck ultrasound. ECG in elderly.
Specialist only: ⚠️ TSH suppression therapy must be initiated and monitored by an endocrinologist or oncologist. Primary care should not independently adjust suppressive doses.
Indian guideline source: ATA 2015 DTC Guidelines (internationally adopted in Indian practice). AIIMS Endocrine Surgery protocols. API Textbook.
⚠️ Key safety warning: Chronic TSH suppression carries risks of: atrial fibrillation (especially in elderly), osteoporosis (especially postmenopausal women), anxiety/insomnia/heat intolerance (symptoms of iatrogenic thyrotoxicosis). Balance tumour suppression benefit against these risks.
Dose adjustment: Regular TSH monitoring (every 3 months initially, then 6 monthly when stable). Adjust in 12.5–25 mcg increments.

4. Secondary (Central) Hypothyroidism

Parameter	Details
Starting dose	12.5–25 mcg/day (⚠️ must exclude adrenal insufficiency FIRST)
Titration	Increase by 12.5–25 mcg every 4–6 weeks
Usual maintenance dose	75–150 mcg/day
Maximum dose	As per primary hypothyroidism
Target	⚠️ Do NOT use TSH to guide dosing — TSH is unreliable in central hypothyroidism. Use fT4 as the primary guide — target fT4 in the upper half of the reference range.

Mandatory Clinical Notes:

When to prefer: Only option for central hypothyroidism (pituitary/hypothalamic disease). [Evidence-based]
When NOT to use without additional precautions: ⛔ NEVER start levothyroxine before ensuring adequate cortisol replacement in patients with suspected panhypopituitarism. Levothyroxine increases cortisol metabolism — can precipitate fatal adrenal crisis. Start hydrocortisone (15–20 mg/day) FIRST, then add levothyroxine 48–72 hours later.
NLEM India status: ✅ Yes.
Time to response: Same as primary hypothyroidism.
Treatment failure: fT4 does not rise despite adequate doses → investigate adherence, malabsorption.
Mandatory baseline: Full pituitary hormone panel (ACTH-cortisol axis is CRITICAL), MRI pituitary.
Specialist only: Yes — Endocrinology.
Indian guideline source: API Textbook. Endocrine Society clinical practice guidelines.
⚠️ Key safety warning: Adrenal crisis risk as stated above. This is one of the most dangerous prescribing errors in endocrinology.
Dose adjustment: Guided by fT4, not TSH.

5. Myxedema Coma (IV Route)

⚠️ Medical emergency. Mortality 20–60% even with treatment. ICU management mandatory.

Route	Loading Dose	Maintenance Dose	Maximum Dose	Notes
IV (preferred)	200–500 mcg IV (most Indian protocols use 200–300 mcg) as single loading dose	50–100 mcg IV once daily until oral intake resumes	500 mcg loading; 100 mcg daily maintenance	⚠️ IV levothyroxine has very limited availability in India.
Oral/NG (when IV unavailable)	300–500 mcg via NG tube (crushed and suspended in water)	100–150 mcg/day via NG tube	—	⚠️ Absorption via NG tube is unpredictable but this approach is commonly used in India when IV formulation is unavailable. Higher oral doses compensate for lower bioavailability.

Mandatory Clinical Notes:

When to prefer IV: Always, when available. IV levothyroxine bypasses unpredictable GI absorption in the critically ill patient.
When NOT to use high loading dose: In elderly with severe cardiac disease — loading dose carries high risk of arrhythmia/MI. Consider lower loading dose (100–200 mcg) with cardiology input.
NLEM India status: ✅ Yes (injection formulation listed).
Time to response: Clinical improvement in 24–48 hours. If no improvement in 48 hours, reassess diagnosis and consider adding liothyronine (T3) 10 mcg IV/NG every 8 hours (specialist only).
Treatment failure: Mortality remains high despite treatment. Poor prognostic factors: advanced age, bradycardia, hypothermia <32°C, high APACHE score.
Mandatory baseline:
- MANDATORY: TSH, fT4, fT3, serum cortisol (MUST draw before starting treatment — but do NOT delay treatment for results), ABG, electrolytes (Na⁺ — hyponatraemia is very common), glucose, FBC, ECG, chest X-ray
- ⚠️ Give IV hydrocortisone 100 mg bolus BEFORE levothyroxine — adrenal insufficiency must be assumed until excluded. Continue hydrocortisone 50 mg every 6–8 hours until cortisol results available.
Specialist only: Yes — ICU/Endocrinology/Critical Care.
Indian guideline source: API Textbook — Myxedema Coma management. AIIMS Endocrinology protocol. Endocrine Society guidelines.
⚠️ Key safety warning: (a) Always give hydrocortisone before levothyroxine. (b) Supportive care is equally critical: passive rewarming (NOT active rewarming — risk of vasodilation and cardiovascular collapse), ventilatory support, IV fluids (hypertonic saline if severe hyponatraemia), treat precipitating factor (infection, stroke, MI, cold exposure, sedative drugs). © Do NOT warm the patient actively.
Dose adjustment: Lower loading dose in cardiac disease. Adjust maintenance based on clinical response and fT4 levels.

Condition-specific notes for myxedema coma:

India-specific challenge: IV levothyroxine is frequently unavailable in most Indian hospitals, including many tertiary centres. The NG tube route using crushed oral tablets is a pragmatic and widely used alternative in Indian practice. API Textbook acknowledges this approach. Some Indian endocrinologists recommend oral loading dose of 300–500 mcg via NG tube followed by 100–150 mcg/day.
Precipitating factors common in India: Cold exposure during North Indian winters (particularly in elderly living alone), undiagnosed/untreated hypothyroidism in remote areas, sedative/opioid administration to undiagnosed hypothyroid patients, infection.

6. Non-Toxic Goitre (TSH Suppressive Therapy for Goitre Reduction)

Parameter	Details
Starting dose	50 mcg/day
Titration	Increase by 25 mcg every 4–6 weeks
Target	TSH 0.3–0.5 mIU/L (mild suppression)
Maximum dose	200 mcg/day
Duration	6–12 months trial. If goitre does not reduce, discontinue.

Mandatory Clinical Notes:

When to prefer: May be considered for small, diffuse, non-toxic goitre in young patients in iodine-sufficient areas with elevated TSH. Historically more commonly used when iodine deficiency was prevalent. [Practice-based]
When NOT to use: ⛔ Not effective for nodular goitre, large goitre causing compressive symptoms (needs surgery), autonomous thyroid nodules. Not recommended in elderly or patients with cardiac disease (risk of iatrogenic thyrotoxicosis). ⚠️ This indication is increasingly discouraged by current guidelines — benefits are marginal and risks (bone loss, atrial fibrillation with prolonged TSH suppression) may outweigh benefits.
NLEM India status: ✅ Yes.
Time to response: Goitre reduction (if any) over 6–12 months.
Treatment failure: No reduction in goitre size after 12 months → discontinue levothyroxine. Consider surgery for symptomatic goitre.
Mandatory baseline: TSH, fT4, thyroid ultrasound, anti-TPO antibodies. FNAC if nodule present.
Specialist vs primary care: Specialist initiation recommended.
Indian guideline source: API Textbook. Indian Thyroid Society.
Key safety warning: Risk of iatrogenic thyrotoxicosis with TSH suppression.
Dose adjustment: Target only mild TSH suppression (0.3–0.5), not full suppression.

Secondary Indications — Adults Only (Off-label, if any)

1. Depression Augmentation — OFF-LABEL

Parameter	Details
Indication	Augmentation of antidepressant therapy in treatment-resistant depression
Dose	25–50 mcg/day (supraphysiological T4 dosing is NOT recommended)
Duration	Trial for 6–8 weeks
Specialist only	Yes — Psychiatry/Endocrinology joint assessment
Label status	OFF-LABEL. ℹ️ Liothyronine (T3) 25–50 mcg/day is more commonly used and better studied for depression augmentation than T4.
Evidence basis	Limited RCT data for T4 augmentation. T3 augmentation has stronger evidence (STAR*D trial). Indian psychiatry practice sometimes uses T4, but T3 is preferred internationally.
Level of evidence	Weak — Limited data for T4; moderate data for T3

2. Infertility — Subclinical Hypothyroidism in Women Undergoing ART — OFF-LABEL but accepted standard practice in India

Parameter	Details
Indication	TSH >2.5 mIU/L in women undergoing assisted reproductive technology (IVF, ICSI)
Dose	25–50 mcg/day to achieve TSH <2.5 mIU/L
Duration	Pre-conception through pregnancy
Specialist only	Reproductive medicine/Endocrinology
Label status	OFF-LABEL but accepted standard practice in India. Most Indian IVF centres treat TSH >2.5 mIU/L before embryo transfer.
Evidence basis	Observational data suggests improved ART outcomes with TSH <2.5. RCT data is mixed (TABLET trial 2019 showed no benefit in euthyroid women with anti-TPO). Indian fertility practice widely adopts this approach.
Level of evidence	Moderate — Observational data + widespread clinical practice; RCT data inconclusive

PAEDIATRIC DOSING (Specialist Only)

General Notes:

⚠️ Congenital hypothyroidism (CH) is a paediatric emergency. Delayed diagnosis and treatment causes irreversible intellectual disability. The critical window for treatment initiation is within the first 2 weeks of life for optimal neurodevelopmental outcomes.
National Newborn Screening Programme (NNSP): Under RBSK (Rashtriya Bal Swasthya Karyakram), India is expanding newborn screening for congenital hypothyroidism. However, coverage remains incomplete in many states. Clinicians must maintain a high index of clinical suspicion (prolonged jaundice, lethargy, poor feeding, constipation, large tongue, umbilical hernia, hoarse cry, delayed skeletal maturation).
Safety monitoring: TSH, fT4 at 2 weeks after initiation, then every 1–2 months for the first year, every 2–3 months from ages 1–3, then every 6–12 months. Also monitor: growth (height/weight), head circumference, developmental milestones.
Minimum age: From birth (congenital hypothyroidism).
Formulation suitability:
- Tablets can be crushed and suspended in a small amount of water/breast milk (1–2 mL) for neonates and infants. ⚠️ Do NOT mix with soy formula (reduces absorption).
- Oral solution (25 mcg/mL) — preferred for neonates/infants if available in India (limited availability).
- Soft gel capsules — NOT suitable for infants.
Palatability: Crushed tablets are essentially tasteless. No palatability concerns.
Paediatric PK: Higher dose per kg required in neonates/infants due to higher metabolic rate, larger Vd relative to body weight, and higher clearance. Dose per kg decreases with increasing age.

Dosing method: Weight-based (mcg/kg/day) for neonates and infants; transition to fixed doses guided by TSH/fT4 in older children.

Adolescent transition: ≥12 years: Approaching adult dosing. Usually 1.0–1.6 mcg/kg/day. Guided by TSH.

Neonatal dosing — SEPARATE SECTION:

Neonatal Congenital Hypothyroidism (NICU/Neonatology Supervision)

⚠️ Start treatment as soon as diagnosis is confirmed — ideally within 2 weeks of life. Do NOT wait for confirmatory testing if screening TSH is significantly elevated (>40 mIU/L).

Parameter	Details
Starting dose	10–15 mcg/kg/day (this is a full replacement dose — NO gradual titration. Start high to normalise thyroid hormones rapidly for brain development)
Typical neonatal dose	Full-term newborn: 37.5–50 mcg/day (based on average birth weight 3–3.5 kg)
Formulation	Crush tablet in 1–2 mL of breast milk or water. Give by oral syringe or spoon. ⚠️ Do NOT mix with soy-based formula.
Target fT4	Upper half of age-specific reference range — within 2 weeks of starting treatment
Target TSH	Normalise TSH (<5 mIU/L) within 4 weeks if possible
Follow-up	TSH and fT4 at 2 weeks after starting, then at 4 weeks, then monthly for first 6 months, then every 2–3 months for first 3 years

Clinical Notes:

If TSH >40 mIU/L on screening: Start treatment immediately with 10–15 mcg/kg/day. Do NOT wait for confirmatory labs.
If TSH 20–40 mIU/L: Confirm with venous sample (TSH + fT4). Start treatment while awaiting results if clinical suspicion is high.
Severe CH (fT4 <5 pmol/L or athyrosis on imaging): May need doses at the higher end (15 mcg/kg/day). Recheck at 2 weeks and increase if fT4 not normalised.
Re-evaluation of diagnosis: At age 3 years, if the child has been compliant and is on a low dose, a trial off treatment (under specialist supervision) can determine if hypothyroidism is permanent or transient.

Primary Indications — Paediatric (Approved / Standard in India)

1. Congenital Hypothyroidism

Age Group	Dose (mcg/kg/day)	Typical Daily Dose	Notes
0–3 months	10–15 mcg/kg/day	37.5–50 mcg	Full dose from day 1. No titration.
3–6 months	8–10 mcg/kg/day	25–50 mcg	Adjust based on TSH/fT4
6–12 months	6–8 mcg/kg/day	50–75 mcg	—
1–5 years	5–6 mcg/kg/day	75–100 mcg	—
6–12 years	4–5 mcg/kg/day	100–125 mcg	—
>12 years	2–3 mcg/kg/day (approaching adult dose)	100–150 mcg	Guided by TSH

Maximum absolute dose: Adult ceiling (200 mcg/day) unless specifically justified.

Clinical Notes:

When to prefer: Levothyroxine is the only treatment for congenital hypothyroidism. No alternatives. [Evidence-based]
When NOT to use: No contraindication in congenital hypothyroidism — treatment is mandatory.
NLEM India status: ✅ Yes.
Time to response: fT4 normalises in 1–2 weeks. TSH normalises in 2–4 weeks.
Treatment failure: Persistent high TSH → check adherence (most common issue), dosing adequacy, absorption (soy formula?).
Mandatory baseline: Confirm with venous TSH + fT4. Thyroid scan (radionuclide or ultrasound) to determine aetiology (athyrosis, ectopic thyroid, dyshormonogenesis) — can be done after starting treatment; do not delay treatment for imaging.
Specialist: Paediatric Endocrinology. If unavailable, neonatologist or paediatrician with guidance from endocrinology.
Indian guideline source: IAP Guidelines on Newborn Screening and Congenital Hypothyroidism (2018). Indian Society for Paediatric and Adolescent Endocrinology (ISPAE) Guidelines. RBSK-NNSP protocol.
⚠️ Key safety warning: Undertreatment (due to inadequate dose or delayed start) causes irreversible intellectual disability. Overtreatment (TSH persistently suppressed <0.5) can cause craniosynostosis, behavioural problems, and advanced bone age. Monitor closely and keep TSH in normal range.
Dose adjustment: Frequent dose adjustments needed in first 3 years due to rapid growth. Weight-based dosing recalculated at each visit.

2. Acquired Hypothyroidism in Children (Hashimoto’s Thyroiditis, Post-Surgical, etc.)

Age Group	Starting Dose	Titration	Usual Maintenance	Maximum
1–5 years	4–6 mcg/kg/day OR 25–50 mcg/day	Adjust by 12.5–25 mcg every 4–6 weeks based on TSH	4–6 mcg/kg/day	200 mcg/day
6–12 years	3–5 mcg/kg/day OR 50–100 mcg/day	Adjust by 25 mcg every 4–6 weeks	3–5 mcg/kg/day	200 mcg/day
>12 years	1.6–2.0 mcg/kg/day OR 50–100 mcg/day	Adjust by 25 mcg every 4–6 weeks	1.0–1.6 mcg/kg/day	200 mcg/day

Clinical Notes:

Hashimoto’s thyroiditis is the most common cause of acquired hypothyroidism in children in India.
Growth monitoring (height velocity) is an important additional outcome measure — catch-up growth should occur with treatment.
In adolescent girls: menstrual irregularities (menorrhagia, oligomenorrhoea) are common presenting features — resolve with euthyroidism.
⚠️ Rapid normalisation of thyroid function in children with chronic severe hypothyroidism can cause pseudotumour cerebri (headache, papilloedema) — start at lower dose (25 mcg) in severely hypothyroid children with very high TSH (>100).

Secondary Indications — Paediatric (Off-label, if any)

No established paediatric off-label indications. Levothyroxine is used only for documented hypothyroidism in children.

MISSED DOSE / DELAYED DOSE GUIDANCE

Dosing frequency: Levothyroxine is taken once daily.

ℹ️ Key principle: Levothyroxine has a very long half-life (6–7 days). Missing a single dose has minimal clinical impact. The body’s T4 pool depletes very slowly.

Scenario	Guidance
Missed dose (same day — any time)	Take as soon as remembered, even if later in the day. Take on an empty stomach (at least 1 hour before or 2 hours after food).
Missed dose (realised next day)	Two acceptable strategies: (a) Take the missed dose AND the current day’s dose together (i.e., double dose for one day). This is safe due to the long half-life. OR (b) Simply skip the missed dose and resume the usual dose the next day. Both approaches are acceptable.
Missed 2–3 consecutive doses	Resume at the usual dose. No re-titration needed. The long half-life means circulating T4 levels drop very slowly.
Missed >7 consecutive doses	Resume at the usual dose. If patient has been off levothyroxine for >2 weeks and is elderly or has cardiac disease, consider restarting at a lower dose and re-titrating (risk of cardiac events from sudden T4 replacement after prolonged hypothyroid state). In otherwise healthy patients, resume at usual dose.
Chronic non-adherence (irregular dosing pattern)	ℹ️ Some endocrinologists recommend once-weekly dosing of the full weekly amount (e.g., 700 mcg once weekly instead of 100 mcg daily) for chronically non-adherent patients — evidence from small studies supports equivalent TSH control. This approach should only be used under specialist supervision.

Steady-state considerations: Steady state takes 4–6 weeks. Intermittent missed doses rarely disrupt steady state meaningfully. Chronic irregular adherence is a more significant problem — leads to fluctuating TSH and difficulty in dose optimisation.

Rebound effects: None. Levothyroxine does not cause rebound hypothyroidism on resumption — simply resumes physiological hormone replacement.

RECONSTITUTION / ADMINISTRATION QUICK REFERENCE

Oral Administration

Parameter	Details
Tablets	⚠️ Take on an EMPTY STOMACH with WATER ONLY. At least 30 minutes (ideally 60 minutes) before breakfast. Do NOT take with milk, tea, coffee, juice, or food.
Timing	First thing in the morning, immediately after waking, is the standard recommendation. Alternative timing: At bedtime (at least 3 hours after dinner) — some studies suggest equivalent TSH outcomes. Bedtime dosing may suit patients who cannot reliably take an early morning dose. Consistency of timing is more important than the specific time chosen.
Crushing/splitting	Tablets may be crushed and suspended in a small amount of water (1–5 mL) for neonates, infants, or patients with swallowing difficulty. Administer immediately after crushing — do not prepare in advance. Scored tablets may be split.
What NOT to mix with	⚠️ Do NOT mix crushed tablet with soy-based formula, soy milk, or high-fibre foods — reduces absorption significantly. Do NOT dissolve in milk or coffee.
Enteral tube	Crush tablet and suspend in 10–20 mL of water. Flush NG/PEG tube with 20–30 mL water before and after administration. ⚠️ Do not administer through the same tube simultaneously with calcium, iron, sucralfate, or antacid formulations — space by at least 4 hours.
Soft gel capsules	Swallow whole with water. Do NOT open, crush, or chew. Take on empty stomach.

IV Administration (Myxedema Coma — ICU Only)

Parameter	Details
Reconstitution	Reconstitute lyophilised powder with 5 mL of NS (0.9% NaCl) or Sterile Water for Injection. Swirl gently — do NOT shake vigorously.
Final concentration	Depends on vial size: 100 mcg vial in 5 mL = 20 mcg/mL; 500 mcg vial in 5 mL = 100 mcg/mL
Administration	Give as slow IV bolus over 5–10 minutes. Do NOT administer as rapid IV push.
Further dilution for infusion	NOT recommended — significant drug adsorption to PVC tubing and IV bags occurs. Give as direct IV bolus only.
Compatible IV fluids	NS (for reconstitution). ⚠️ Do NOT add to large-volume IV bags (D5W, NS, RL) for infusion — loss of drug to container/tubing adsorption.
Incompatible	Do not mix with any other drug in the same syringe.
Infusion pump	Not applicable — direct IV bolus administration.

Stability After Reconstitution

Condition	Stability
Reconstituted solution (room temperature)	Use immediately. Discard unused portion.
Reconstituted solution (refrigerated)	Use within 4 hours if refrigerated, though immediate use is preferred.
Protect from light	Yes — protect from light.

Multi-Dose Vial Handling

Not applicable — supplied as single-use lyophilised vials.

Cold-Chain Drug Guidance

Tablets: Not a cold-chain drug. Store below 25°C. Protect from moisture and light. ℹ️ In Indian summer conditions (>40°C), store in a cool, dry cupboard away from direct sunlight. Do not store in bathrooms (moisture). Some endocrinologists recommend refrigerating tablets in very hot climates — this is acceptable but not mandatory.
IV vials: Store below 25°C. Do not freeze. Protect from light.

Weight-Based Dosing Calculation Example (Paediatric — Congenital Hypothyroidism)

Example: 3.5 kg newborn, dose 12 mcg/kg/day:

Dose = 12 × 3.5 = 42 mcg/day
Round to nearest available tablet: use 50 mcg tablet (slight overestimation acceptable — recheck TSH at 2 weeks and adjust)
Crush 50 mcg tablet and suspend in 2 mL water, give 1.7 mL using oral syringe (for 42 mcg), OR give the full 50 mcg (acceptable at neonatal replacement doses)
Administer in the morning, before feeding, on empty stomach

Storage

Condition	Guidance
Tablets	Store below 25°C, protected from moisture and light. Keep in original strip packaging.
Soft gel capsules	Store below 25°C. Protect from moisture.
IV vials (lyophilised powder)	Store below 25°C. Protect from light. Do not freeze.

RENAL ADJUSTMENT

eGFR formula used: Not applicable — levothyroxine does not require renal dose adjustment.

eGFR (mL/min)	Dose Adjustment	Notes
>60	No adjustment required	—
30–60	No adjustment required	—
15–30	No adjustment required	CKD may alter thyroid hormone metabolism (reduced T4→T3 conversion, altered TBG). Monitor TSH and adjust dose based on TSH.
<15 (non-dialysis)	No adjustment required	⚠️ Monitor TSH — CKD can cause “sick euthyroid”-like pattern. Treat true hypothyroidism; do not treat isolated low T3 of CKD.
Haemodialysis	No supplemental dose post-HD	Not removed by haemodialysis (>99.97% protein bound). ⚠️ HD patients have higher prevalence of hypothyroidism. Monitor TSH every 6 months in HD patients.
Peritoneal dialysis	No adjustment	—
CRRT	No adjustment	—

ARC (Augmented Renal Clearance): Not relevant — levothyroxine is not renally cleared.

Source: CDSCO product insert; API Textbook.

HEPATIC ADJUSTMENT

Severity	Dose Guidance
Mild (Child-Pugh A)	No dose adjustment required.
Moderate (Child-Pugh B)	No specific dose adjustment. TBG levels may be altered in cirrhosis (decreased hepatic synthesis → lower total T4, but free T4 usually normal). Monitor fT4 in addition to TSH.
Severe (Child-Pugh C)	No specific dose adjustment. Severe liver disease may impair T4→T3 conversion and alter TBG levels. Monitor fT4 and TSH. Dose guided by TSH/fT4. Specialist guidance recommended.

No formal Child-Pugh-based dosing data available. Clinical guidance is based on pharmacokinetic principles: levothyroxine metabolism (peripheral deiodination) is partially hepatic but also occurs extensively in kidney, muscle, and other tissues. Severe liver disease alone rarely necessitates dose change — adjust based on TSH.

No clinically significant active metabolites that accumulate in liver disease (T3 is the active metabolite but its production is distributed across many tissues).
Protein binding (TBG): Severe liver disease reduces TBG synthesis → lower total T4. However, free T4 (fT4) is the clinically relevant measurement and remains the guide for dosing in liver disease.

Concurrent hepatotoxin note: Levothyroxine itself is not hepatotoxic. No additional LFT monitoring needed for levothyroxine. However, drugs that alter hepatic enzyme activity (rifampicin, carbamazepine, phenytoin, phenobarbital) increase T4 clearance and may require dose increase (see Drug Interactions).

CONTRAINDICATIONS

Contraindication	Clinical Rationale
⛔ Untreated adrenal insufficiency	Levothyroxine increases cortisol metabolism. Starting T4 without adequate cortisol replacement → adrenal crisis (hypotension, shock, potentially fatal). Always treat adrenal insufficiency first.
⛔ Untreated thyrotoxicosis	Levothyroxine in a thyrotoxic patient worsens hyperthyroidism — potentially fatal thyroid storm. ⚠️ Rarely a prescribing error, but can occur if TSH is suppressed due to thyrotoxicosis and is misinterpreted as needing T4.
⛔ Acute myocardial infarction (relative — specialist decision)	High-dose levothyroxine increases myocardial oxygen demand → can extend infarct. If hypothyroid patient has acute MI, T4 replacement should be cautious (low dose) and cardiologist-guided.
⛔ Known hypersensitivity to levothyroxine or any excipient (rare)	Allergic reactions are extremely rare — most “allergies” are reactions to excipients (dyes, lactose) rather than the hormone itself. Switch brands/formulations.

Allergy Cross-Reactivity:

True allergy to the levothyroxine molecule is essentially non-existent (it is identical to endogenous T4). Reactions are almost always due to excipients (dyes, fillers, lactose, acacia, cornstarch).
If a patient reports “allergy to thyroid medicine” — investigate which brand, which symptoms. Try a different brand with different excipients, or use soft gel capsule formulation (fewer excipients), or compounding pharmacy (specialist guidance).

CAUTIONS

⚠️ High-Priority Cautions

Condition	Concern	Monitoring Required
Coronary artery disease / Ischaemic heart disease	Levothyroxine increases heart rate, myocardial oxygen demand, and contractility. Risk of angina, MI, arrhythmia.	⚠️ Start at 12.5–25 mcg/day. Increase by 12.5–25 mcg every 4–6 weeks. ECG before starting and with dose increases. Cardiology input for significant CAD.
Atrial fibrillation (existing or history)	Overtreatment (suppressed TSH) significantly increases AF risk.	Keep TSH in normal range (0.5–4.0) unless thyroid cancer suppression indicated. ECG periodically.
Osteoporosis (or high risk)	Chronic overtreatment (suppressed TSH) accelerates bone loss, especially in postmenopausal women.	DEXA scan at baseline if TSH suppression therapy planned. Monitor bone density every 1–2 years. Ensure adequate calcium and vitamin D.
Diabetes mellitus	Achieving euthyroid state may increase insulin/OHA requirements (T4 increases glucose metabolism). Conversely, hypothyroidism masks true insulin requirement — treating it unmasks higher requirements.	Monitor blood glucose when starting or significantly adjusting levothyroxine dose. Adjust diabetes medications accordingly.
Adrenal insufficiency (treated)	Even if on hydrocortisone, dose may need increase when starting levothyroxine (increased cortisol metabolism).	Review hydrocortisone dose when starting/increasing levothyroxine.
Elderly (≥60 years)	See Elderly section. Lower dose requirement, higher cardiac risk.	Start low (12.5–25 mcg). Slow titration.
Long-standing severe hypothyroidism	Sudden full replacement can cause cardiac arrhythmia, heart failure, adrenal crisis.	Start low, go slow. In children with severe CH, caution about pseudotumour cerebri.

Standard Cautions

Condition	Concern
Seizure disorder	Levothyroxine may lower seizure threshold at initiation (rare). Monitor seizure frequency during dose initiation.
Autonomic neuropathy (diabetic)	May not tolerate cardiovascular effects of T4 replacement as well.
Malabsorption (coeliac disease, inflammatory bowel disease, post-bariatric surgery)	Higher dose requirements. Erratic absorption. Monitor TSH more frequently.
Patients on anticoagulants (warfarin)	Levothyroxine potentiates warfarin effect. See Drug Interactions.

PREGNANCY

Parameter	Details
Overall safety statement	⚠️ Levothyroxine is ESSENTIAL during pregnancy if the mother is hypothyroid. Untreated maternal hypothyroidism causes: miscarriage, preeclampsia, placental abruption, preterm birth, low birth weight, and IMPAIRED FETAL NEURODEVELOPMENT (lower IQ in offspring). Levothyroxine is safe in pregnancy — it is a replacement of a physiological hormone.
Teratogenicity	None. Levothyroxine is not teratogenic at therapeutic doses. It is a physiological hormone replacement identical to endogenous T4.
First trimester	⚠️ Critical period. Fetal thyroid gland does not begin functioning until 12–14 weeks. Before this, the fetus is entirely dependent on maternal T4 for brain development. Adequate maternal T4 in the first trimester is essential.
Second and third trimesters	Continued adequate dosing essential. Dose requirement typically increases by 25–50% over pre-pregnancy dose.
Dose increase in pregnancy	⚠️ Increase dose as soon as pregnancy is confirmed — do NOT wait for elevated TSH. Practical approach: (a) Empirically increase dose by 25–30% immediately upon positive pregnancy test (e.g., if on 100 mcg, increase to 125 mcg), OR (b) Add 2 extra tablets per week at the current dose (e.g., take 9 tablets/week instead of 7). Check TSH immediately and at 4 weeks.
TSH target in pregnancy	Trimester-specific: 1st trimester: TSH <2.5 mIU/L (some guidelines accept <4.0 with population-specific ranges — Indian Thyroid Society recommends <2.5 in 1st trimester). 2nd and 3rd trimester: TSH <3.0 mIU/L.
Monitoring — mother	TSH every 4–6 weeks during first half of pregnancy. At least once in third trimester. fT4 if central hypothyroidism.
Monitoring — fetus	Standard antenatal monitoring. Neonatal thyroid screening at birth.
Pre-conception counselling	⚠️ All women with hypothyroidism planning pregnancy should have TSH checked before conception. Aim for TSH <2.5 mIU/L pre-conception. Optimise levothyroxine dose before conception. Folic acid 5 mg/day pre-conception.
Preferred alternatives	None needed — levothyroxine IS the treatment. T4+T3 combination is NOT recommended in pregnancy (T3 crosses placenta poorly and may not benefit fetal brain development).
Post-partum	Dose should be reduced back to pre-pregnancy dose at delivery. Recheck TSH at 6–8 weeks post-partum.
Contraception requirements	Not applicable.

Pregnancy Prevention Programme / Registry: Not applicable.

Fertility Effects

Hypothyroidism itself (untreated) causes: anovulation, luteal phase deficiency, hyperprolactinaemia, menorrhagia, and subfertility in women; oligospermia and erectile dysfunction in men.
Levothyroxine treatment restores fertility by normalising thyroid function.
Levothyroxine itself does not impair fertility — it improves it by treating hypothyroidism.
No washout period before conception — levothyroxine should be CONTINUED and INCREASED in pregnancy.

LACTATION

Parameter	Details
Compatible with breastfeeding	Yes — fully compatible. Levothyroxine is a physiological hormone. Small amounts are excreted in breast milk, as expected for an endogenous hormone. This contributes negligibly to infant thyroid status.
Drug levels in breast milk	Very low. The amount of T4 in breast milk is insufficient to prevent or treat infant hypothyroidism. RID not formally calculated because levothyroxine is not considered a “drug” in the traditional sense — it is a physiological replacement.
Preferred alternatives	None needed — levothyroxine IS the standard treatment and is fully compatible with breastfeeding.
Monitoring in infant	No specific monitoring of infant needed related to maternal levothyroxine use. All neonates should undergo standard newborn thyroid screening regardless.
Timing advice	No timing adjustment needed. Take levothyroxine at the usual time (empty stomach, morning).

Effect on milk production: Hypothyroidism (untreated) can reduce milk production. Adequate levothyroxine treatment supports normal lactation by maintaining euthyroid state. No adverse effect on milk production.

Temporary incompatibility: Not applicable — always compatible.

ELDERLY

Definition: ≥60 years (per Indian Census / National Programme for Health Care of the Elderly). Specific drug data for very elderly (≥75–80 years) noted separately where relevant.

Parameter	Details
Recommended starting dose	12.5–25 mcg/day
Titration	Increase by 12.5–25 mcg every 6–8 weeks (slower than in younger adults where 4-week intervals are acceptable)
Usual maintenance dose	50–100 mcg/day (lower than younger adults — average requirement ~1.0 mcg/kg/day vs 1.6 mcg/kg/day in young adults)
Maximum dose	150 mcg/day (higher doses only with cardiology/endocrinology joint supervision)

Extra Risks Specific to Elderly:

Risk	Details
⚠️ Cardiac events	Most important risk. Excessive levothyroxine increases myocardial oxygen demand → angina, MI, arrhythmia. Start low, go slow.
⚠️ Atrial fibrillation	Even mildly suppressed TSH (<0.5) significantly increases AF risk in elderly. Avoid overtreatment.
Osteoporosis	Chronic overtreatment accelerates bone loss. Very important in postmenopausal women. DEXA monitoring if on suppressive doses.
Falls	Overtreatment → AF, dizziness, tremor → falls.
Overdiagnosis	⚠️ TSH reference range may be higher in elderly (especially >70 years). A TSH of 5.0–7.0 mIU/L may be NORMAL in a healthy 80-year-old. NHANES III data shows TSH upper limit increases with age. Treating “subclinical hypothyroidism” in very elderly patients can be harmful. TRUST trial (2017) showed no benefit of levothyroxine for SCH in >65 years with TSH 4.6–19.9.

Beers Criteria / STOPP-START:

Not specifically listed in Beers Criteria (it is not an inappropriate drug — it is necessary when truly indicated).
STOPP: Avoid TSH suppression beyond target range (risk of AF and osteoporosis).
START: Consider thyroid function testing in elderly patients with unexplained fatigue, cognitive decline, depression, constipation, or dyslipidaemia.

Common Indian clinical scenario: 72-year-old woman with TSH 6.5 mIU/L found on routine screening, asymptomatic, on amlodipine and atorvastatin.

⚠️ Do NOT start levothyroxine automatically. This is likely age-appropriate TSH.
Repeat TSH in 6–8 weeks. Check anti-TPO antibodies.
If anti-TPO negative and asymptomatic: observe with annual TSH monitoring.
If anti-TPO positive OR symptomatic: consider trial of low-dose levothyroxine (25 mcg) with reassessment at 3–6 months.

Deprescribing guidance:

When to consider stopping: If levothyroxine was started for borderline TSH elevation (5–10 mIU/L) without symptoms, and the patient is now >75 years, consider trial discontinuation under specialist supervision.
Tapering: No pharmacological need to taper (long half-life means gradual decline in levels after stopping). Can stop abruptly — TSH will rise gradually over 4–6 weeks.
Expected withdrawal effects: If the patient truly has hypothyroidism, symptoms will gradually return over 4–8 weeks (fatigue, constipation, cold intolerance). If they don’t, the original diagnosis may have been incorrect.
Monitor after stopping: TSH at 6–8 weeks and 12 weeks after stopping.

MAJOR DRUG INTERACTIONS

⚠️ Levothyroxine has one of the most extensive absorption interaction profiles of any medication. The majority of interactions are at the level of GI absorption — drugs that bind T4 in the gut or alter gastric pH significantly reduce levothyroxine bioavailability. These interactions are the most common cause of apparent “treatment failure” in Indian practice.

Interacting Drug/Substance	Mechanism	Clinical Effect	Onset Type	Action Required
⛔ Calcium carbonate / Calcium citrate	Binds levothyroxine in the GI tract, forming insoluble calcium-T4 complex	20–25% reduction in T4 absorption. TSH rises.	Gradual (days to weeks)	⚠️ Separate by at least 4 hours. Levothyroxine FIRST in morning, calcium after lunch/dinner. This is the MOST COMMON drug interaction causing levothyroxine treatment failure in India (calcium is widely prescribed, especially in women).
⛔ Iron supplements (ferrous sulfate, ferrous fumarate, carbonyl iron)	Binds levothyroxine in GI tract	Similar magnitude as calcium — significant absorption reduction	Gradual	⚠️ Separate by at least 4 hours. Levothyroxine morning empty stomach → iron after lunch. Extremely common co-prescription in Indian women (anaemia + hypothyroidism is very prevalent).
⛔ Aluminium-containing antacids (aluminium hydroxide)	Binds levothyroxine in GI tract	Significant absorption reduction	Gradual	Separate by at least 4 hours.
⛔ Sucralfate	Binds levothyroxine in GI tract (aluminium content)	Significant absorption reduction	Gradual	Separate by at least 4 hours. Not commonly co-prescribed but important in patients with peptic disease.
⛔ Cholestyramine / Colestipol / Colesevelam	Bile acid sequestrants bind thyroid hormones in gut; interrupt enterohepatic recycling of T4	30–50% reduction in T4 absorption and recycling	Gradual	⚠️ Separate by at least 4–6 hours. May need significant levothyroxine dose increase.
⛔ Sevelamer	Phosphate binder — binds T4 in gut (similar to calcium)	Significant absorption reduction	Gradual	Separate by at least 4 hours. Common in CKD patients on dialysis.
⚠️ Rifampicin	Potent inducer of hepatic glucuronidation and deiodination → increases T4 clearance	25–50% increase in T4 clearance. TSH rises. Requires levothyroxine dose increase.	Gradual (1–2 weeks for full induction effect)	Increase levothyroxine dose by 25–50% during rifampicin therapy. Monitor TSH at 4–6 weeks after starting and after stopping ATT. Extremely important in India — TB-hypothyroidism co-occurrence is common.
⚠️ Phenytoin / Carbamazepine / Phenobarbital	Hepatic enzyme induction → increased T4 clearance. Also displace T4 from protein binding.	Increased T4 requirement. TSH may rise.	Gradual (1–2 weeks)	Increase levothyroxine dose. Monitor TSH at 4–6 weeks.
⚠️ Oestrogens (OCP, HRT, tamoxifen)	Increase TBG synthesis → increased T4 binding → decreased free T4 → compensatory TSH rise	May need 25–50% dose increase in levothyroxine	Gradual (weeks)	Monitor TSH at 4–6 weeks after starting/stopping oestrogen. Very common interaction in Indian women on OCP + levothyroxine.
⚠️ Warfarin	Levothyroxine increases catabolism of vitamin K-dependent clotting factors → potentiates anticoagulant effect	INR rises (risk of bleeding) when hypothyroid patient becomes euthyroid on levothyroxine	Gradual (weeks)	Monitor INR frequently when starting levothyroxine in a patient on warfarin. May need warfarin dose REDUCTION.

MODERATE DRUG INTERACTIONS

Interacting Drug/Substance	Mechanism	Clinical Effect	Monitoring/Action
Proton pump inhibitors (PPIs) (omeprazole, pantoprazole, rabeprazole)	Increased gastric pH reduces dissolution of levothyroxine tablets (T4 requires acidic pH for optimal dissolution)	20–30% reduction in T4 absorption in some patients. More significant with chronic PPI use.	Monitor TSH at 6–8 weeks after starting PPI. May need levothyroxine dose increase of 25–50 mcg. Very common co-prescription in India — PPIs are overprescribed. Consider switching to soft gel capsule (pH-independent absorption) or H2RA.
H2-receptor antagonists (ranitidine, famotidine)	Increased gastric pH (less potent than PPIs)	Mild reduction in absorption (less than PPIs)	Monitor TSH. Usually no dose adjustment needed. Preferable to PPIs if acid suppression needed in levothyroxine-treated patients.
Metformin	Mechanism unclear — may alter TSH levels independent of T4 absorption. Some studies show TSH reduction in hypothyroid diabetics starting metformin.	Mild TSH decrease — may appear as overtreatment	Monitor TSH when starting/stopping metformin in hypothyroid diabetic patients. Usually no dose adjustment needed.
Raloxifene	Binds levothyroxine in GI tract	Moderate absorption reduction	Separate by 4 hours. Monitor TSH.
Orlistat	May reduce T4 absorption (fat malabsorption)	May increase levothyroxine requirement	Separate by 4 hours. Monitor TSH.
Sertraline	May modestly increase T4 clearance (mechanism unclear — possibly enhanced T4 deiodination)	May require modest dose increase	Monitor TSH when starting/stopping sertraline. Usually minor.
Ciprofloxacin / Levofloxacin	Chelation of T4 (if co-ingested with multivalent cations in the same formulation)	Variable absorption reduction	Separate by at least 2 hours.
Soy products / Soy formula	Soy isoflavones inhibit thyroid peroxidase and may bind T4 in gut	Reduced T4 absorption. More significant in infants on soy formula.	⚠️ Counsel patients to avoid large quantities of soy products near levothyroxine timing. In infants with CH, use non-soy formula.
Coffee	Coffee (including decaf) reduces T4 absorption if consumed simultaneously	May reduce absorption by 25–30%	⚠️ Do NOT take levothyroxine with coffee. Wait at least 30–60 minutes after taking levothyroxine before drinking coffee. This is the single most practical counselling point in India — “chai” (tea) and coffee with morning medication is an extremely common Indian habit.
High-fibre diet	Dietary fibre binds T4 in gut	May reduce absorption modestly	Advise consistent fibre intake (not excessive) and maintain levothyroxine timing 30–60 min before meals.
Biotin supplements	Biotin does NOT interact with levothyroxine pharmacokinetically but INTERFERES WITH THYROID ASSAYS	⚠️ Biotin causes falsely low TSH and falsely high fT4/fT3 on streptavidin-biotin immunoassays → can mimic hyperthyroidism/Graves’ disease → inappropriate dose reduction or unnecessary investigations	Stop biotin supplements for at least 2 days (ideally 7 days) before thyroid function testing. This is increasingly relevant in India as biotin-containing “hair/skin/nail” supplements and multivitamins are very popular.

COMMON ADVERSE EFFECTS

ℹ️ Key principle: When levothyroxine is dosed correctly to maintain euthyroid state, it has essentially NO true adverse effects — it is replacing a physiological hormone. Virtually all “side effects” of levothyroxine are symptoms of OVERTREATMENT (iatrogenic thyrotoxicosis) or UNDERTREATMENT (persistent hypothyroidism).

Frequency	System	Adverse Effect	Notes
Very common if OVERTREATED (TSH suppressed)	CVS	Palpitations, tachycardia	Dose-dependent. First sign of overtreatment in many patients. Reduce dose.
Very common if overtreated	CNS	Anxiety, nervousness, insomnia, irritability	Reduce dose.
Very common if overtreated	Metabolic	Heat intolerance, excessive sweating	—
Very common if overtreated	GI	Diarrhoea, increased appetite	—
Very common if overtreated	Musculoskeletal	Tremor (fine)	Dose-dependent.
Very common if overtreated	Metabolic	Weight loss (unintentional)	—
Common during dose titration	Musculoskeletal	Temporary hair loss / increased hair shedding	Very commonly reported in Indian clinical practice. ⚠️ Occurs during dose adjustment phase (both when starting treatment AND when dose is changed). Usually TRANSIENT — resolves in 2–3 months once stable euthyroid state achieved. Counsel patients proactively as this causes significant anxiety.
Common during dose titration	CNS	Headache	Usually transient.
Common (excipient-related)	Dermatological	Rash, urticaria	Almost always due to excipients (dyes, fillers, lactose) in specific brands — NOT due to levothyroxine itself. Switch brands.

Dose-response note: All cardiovascular and CNS symptoms are directly related to the degree of overtreatment. Reducing dose by 12.5–25 mcg usually resolves symptoms within 1–2 weeks (though TSH takes 4–6 weeks to re-equilibrate).

SERIOUS ADVERSE EFFECTS

Adverse Effect	Frequency	Details
⚠️ Angina pectoris / Myocardial infarction	Rare (primarily in patients with pre-existing CAD)	Occurs when: full replacement dose given to elderly/cardiac patients without gradual titration, OR significant overtreatment in any patient. Requires immediate dose reduction and cardiology review. No specific antidote — standard ACS management.
⚠️ Cardiac arrhythmias (atrial fibrillation, supraventricular tachycardia)	Uncommon	Occurs with overtreatment (suppressed TSH). Risk increases with age. AF may be the first manifestation of overtreatment in elderly. Reduce dose. Rate control as per standard AF management.
⚠️ Heart failure exacerbation	Rare	In patients with pre-existing heart failure, excessive T4 increases cardiac workload. Start very low dose.
Seizures (in context of rapid correction)	Very rare	Reported in patients with severe longstanding hypothyroidism started on full replacement doses — sudden metabolic shift. Start low.
Osteoporotic fractures (long-term overtreatment)	Not an acute event; cumulative risk	Chronic TSH suppression (especially in postmenopausal women) accelerates bone loss. Monitor bone density.
Adrenal crisis (if adrenal insufficiency unrecognised)	Rare but potentially fatal	⛔ Levothyroxine increases cortisol metabolism. Undiagnosed adrenal insufficiency + levothyroxine → acute adrenal crisis. Always check cortisol axis in suspected panhypopituitarism before starting T4. Antidote: IV hydrocortisone 100 mg bolus, then 50 mg every 6–8 hours. Available at all levels of healthcare in India.
Pseudotumour cerebri (in children)	Rare	Reported in children with severe chronic hypothyroidism started on high replacement doses. Symptoms: headache, vomiting, papilloedema. Reduce dose temporarily.
Craniosynostosis (in infants — chronic overtreatment)	Very rare	Reported with prolonged overtreatment in infants (persistently suppressed TSH). Monitor head circumference and fontanelle.

⚠️ PvPI Reporting: Report all serious adverse effects to the nearest ADR Monitoring Centre under PvPI (Pharmacovigilance Programme of India) or via the ADR reporting form on the CDSCO website.

CDSCO safety alerts / Black box equivalent: No specific CDSCO black box warning. However, CDSCO product inserts carry the standard warning against use of thyroid hormones for weight loss in euthyroid patients — doses sufficient for weight loss are doses that cause thyrotoxicosis with its attendant cardiac risks.

Early warning signs for patient education:

Racing heartbeat, chest pain, breathlessness → overtreatment or cardiac event → urgent medical review
Excessive hair fall → dose adjustment phase (usually self-limiting) but reassess dose
Rash → likely excipient allergy → try different brand

MONITORING REQUIREMENTS

Baseline (Before Starting)

Parameter	Priority	Details
TSH	MANDATORY	Confirm hypothyroidism. Document baseline.
Free T4 (fT4)	MANDATORY	Confirms severity. Essential in central hypothyroidism (where TSH is unreliable).
Anti-TPO antibodies	RECOMMENDED	Confirms autoimmune aetiology (Hashimoto’s). Predicts need for lifelong treatment. Guides management in SCH.
ECG	MANDATORY in elderly (≥60) and cardiac disease; RECOMMENDED in all adults	Baseline cardiac rhythm. Detect pre-existing AF, ischaemic changes.
Lipid profile	RECOMMENDED	Hypothyroidism causes dyslipidaemia — will improve with treatment. Establishes baseline.
Serum cortisol / 8 AM cortisol	MANDATORY if central hypothyroidism or panhypopituitarism suspected	⛔ Rule out adrenal insufficiency before starting T4.
FBC	RECOMMENDED	Anaemia screening (hypothyroidism causes macrocytic anaemia).
Vitamin D, Vitamin B12	OPTIONAL but commonly done in India	Frequently low in Indian hypothyroid patients. Treating deficiencies improves overall well-being.
Weight	RECOMMENDED	Baseline for tracking.
Thyroid ultrasound	OPTIONAL	Only if goitre or nodules palpable. NOT routine for biochemical hypothyroidism without clinical findings.

Resource-limited surrogates: In PHC/CHC settings where fT4, anti-TPO, and lipid profile are not available: TSH alone is sufficient to diagnose and manage primary hypothyroidism. Clinical assessment (heart rate, weight, skin, reflexes, symptom checklist) can serve as surrogate for dose adequacy between TSH checks.

After Initiation / Dose Change

Parameter	Timing
TSH	4–6 weeks after starting or after ANY dose change. ⚠️ Do NOT check TSH earlier — it has not equilibrated.
fT4	At same time as TSH (especially in central hypothyroidism where fT4 guides dosing).
Clinical symptom assessment	At each visit — especially cardiovascular symptoms (palpitations, chest pain), hair loss, weight changes.
ECG	Repeat if dose increased significantly in elderly/cardiac patients.

Long-Term / Maintenance

Parameter	Frequency
TSH	Every 6–12 months once stable dose achieved. More frequently if dose change, new medication, pregnancy, or clinical change.
fT4	Annually or with TSH if central hypothyroidism.
Lipid profile	Annually for first 2 years, then every 2–3 years.
Weight	Every 6 months.
Bone density (DEXA)	Every 2 years in postmenopausal women on TSH-suppressive doses (thyroid cancer). Not routinely needed for replacement doses with normal TSH.
Cardiac monitoring	ECG annually in elderly or cardiac patients.

Therapeutic Drug Monitoring (TDM)

Not applicable in the traditional sense. However, TSH IS the primary “TDM” tool for levothyroxine — it reflects the body’s response to thyroid hormone levels. Target TSH: 0.5–4.0 mIU/L (general), <2.5 (pregnancy 1st trimester), <0.1–0.5 (thyroid cancer suppression). Serum T4/T3 levels are NOT routinely used for dose adjustment in primary hypothyroidism — TSH is the guide.

When to Stop Monitoring

Monitoring should NEVER be stopped — levothyroxine treatment for hypothyroidism is lifelong in most cases (permanent hypothyroidism).
Exception: Transient hypothyroidism (postpartum thyroiditis, subacute thyroiditis, drug-induced). In these cases, levothyroxine may be tapered and stopped after 6–12 months with TSH monitoring to confirm recovery.
Annual TSH monitoring is the minimum lifelong requirement.

PATIENT COUNSELLING

(Ready reference for the prescribing clinician to use during patient communication)

What this medicine is for:
“This medicine replaces a hormone that your thyroid gland is not making enough of. This hormone controls your body’s energy, growth, and many other functions. Without enough of it, you feel tired, cold, constipated, and gain weight.”

How to take it:

“⚠️ Take this tablet FIRST THING IN THE MORNING, ON AN EMPTY STOMACH, WITH PLAIN WATER ONLY.”
“Wait at least 30–60 minutes before eating breakfast, drinking tea, coffee, or milk.”
“Take it at the SAME TIME every day.”
“Do NOT take it with tea, coffee, milk, juice, or any food — this stops the medicine from being absorbed properly.”
“If you also take calcium tablets, iron tablets, or antacids — take them at least 4 HOURS AFTER your thyroid medicine (e.g., with lunch or dinner, not in the morning).”

What to do if you miss a dose:
“If you forget your morning dose, take it as soon as you remember — even if it is later in the day — on an empty stomach. If you don’t remember until the next day, you can take two tablets together (yesterday’s missed dose + today’s dose) — this is safe because this medicine has a very long-lasting effect in the body.”

Common side effects to expect:
"When the dose is correct, this medicine has no real side effects — it is simply replacing what your body should be making naturally.

You may notice some hair shedding when you first start the medicine or when the dose is changed — this is temporary and will settle in 2–3 months.
If you feel your heart racing, feel anxious, cannot sleep, or are losing weight — your dose may be too high. Tell your doctor."

Warning signs to report immediately:
"Come to the doctor if:

Your heart is racing, pounding, or beating irregularly
You have chest pain or breathlessness
You feel very anxious, shaky, or unable to sleep
You develop a rash (tell your doctor which brand you are taking — a different brand may suit you better)"

Things to avoid:

“Do NOT take with tea, coffee, milk, or food — always plain water, empty stomach”
“Do NOT take calcium or iron tablets at the same time”
“Do NOT stop this medicine on your own — most people need it for life”
“Do NOT use this medicine for weight loss — it is not a weight loss pill and using it for this purpose is dangerous”
“If you are taking biotin supplements (for hair/skin), stop them at least 2 days before your blood test — they can give wrong thyroid test results”

Storage:
“Keep in a cool, dry place below 25°C. Protect from moisture and sunlight. In Indian summers, store in the coolest part of the house — not in the kitchen or bathroom.”

Duration:
“⚠️ This is usually a LIFELONG medicine. Your thyroid gland is not making enough hormone, and this medicine replaces it. Do not stop it because you feel better — feeling better means the medicine is working.”

Follow-up:
"Blood tests (thyroid test — TSH) are needed:

4–6 weeks after starting or after any dose change
Then every 6–12 months once your dose is stable
More often if you become pregnant or if other medicines change"

Common Patient Questions

“Can I take this with my other medicines?” — “Take thyroid medicine ALONE with water. All other medicines should be taken at least 30–60 minutes later (after breakfast). Calcium, iron, and antacid — at least 4 hours later.”
“Can I take this during fasting (Ramadan/Navratri)?” — “Yes. Take your thyroid medicine early in the morning with water before suhoor. If fasting during Navratri, take it first thing in the morning with water — it can be taken before any food. This medicine does not break a fast.”
“Will this affect my ability to drive or work?” — “No. When your dose is correct, this medicine has no effect on alertness or driving ability.”
“Is this medicine habit-forming?” — “No. This is a hormone replacement — like insulin for diabetes. Your body needs it because your thyroid isn’t making enough on its own.”
“Can I stop once I feel better?” — “⚠️ No — feeling better means the medicine is working. If you stop, your symptoms will return in a few weeks. Most people need this medicine for life.”
“I’ve heard thyroid medicine causes hair fall — is that true?” — “When you start the medicine or when the dose changes, some temporary hair shedding is normal. This settles in 2–3 months. In fact, hypothyroidism ITSELF causes hair fall — the medicine actually helps your hair grow back over time.”
“My friend is on a different brand. Should I switch?” — “Different brands may work slightly differently for some people. If you are doing well on your current brand, do not switch without discussing with your doctor. If cost is a concern, discuss generic options.”
“Can I take this during pregnancy?” — “⚠️ Yes — you MUST continue taking it during pregnancy, and your dose usually needs to increase. Inform your doctor as soon as you become pregnant so the dose can be adjusted.”

Caregiver/Family Counselling

(For elderly patients, neonates/infants with congenital hypothyroidism)

"For infants with thyroid problems:

Crush the tablet and mix with a small amount (1–2 mL) of breast milk or water. Do NOT mix with soy milk.
Give on an empty stomach before feeding — ideally 30 minutes before.
This is extremely important for your baby’s brain development — do not miss doses.
Bring the baby for regular check-ups and blood tests as advised.

For elderly patients:

Ensure the medicine is taken on an empty stomach every morning with water only.
Watch for signs of too much medicine: racing heartbeat, anxiety, trembling, inability to sleep — report to doctor."

India-Specific Adherence Support

Cost: “Levothyroxine is one of the cheapest medicines available. Generic brands cost ₹1–2 per tablet. A month’s supply costs ₹30–60. There is no reason to skip doses due to cost. Jan Aushadhi stores may stock it at even lower prices.”
“Thyroid is lifelong” acceptance: “In India, many patients resist taking a ‘lifelong’ medicine. Explain: This is like glasses for poor eyesight — your thyroid is weak, and this medicine simply gives your body what it cannot make on its own. It is safe, cheap, and keeps you healthy.”
Hot climate storage: “In Indian summer (>40°C), store in the coolest, driest part of the house. Do not store in the kitchen (heat, steam) or bathroom (moisture). Keep in bedroom cupboard. Some people keep it in the fridge — this is fine.”
Rural access: “If you cannot get your usual brand in a smaller town, any brand of levothyroxine in the same strength is acceptable for short-term use. Inform your doctor at the next visit if you switched brands, as dose may need minor adjustment.”

BRANDS AVAILABLE IN INDIA

Jan Aushadhi / PMBJP: Levothyroxine sodium tablets (25 mcg, 50 mcg, 100 mcg) are available at Jan Aushadhi Kendras at significantly reduced prices. This should be the first recommendation for cost-sensitive patients.

Brand Name	Manufacturer	Key Strengths (mcg)	Availability
Levothyroxine — Jan Aushadhi	PMBJP	25, 50, 100	Available at Jan Aushadhi Kendras. Most affordable option.
Thyronorm	Abbott India (originator brand in India)	12.5, 25, 50, 75, 88, 100, 112, 125, 137, 150, 175, 200	Widely available — most commonly prescribed brand in India. Widest range of tablet strengths.
Eltroxin	Mylan/Viatris (formerly GlaxoSmithKline)	25, 50, 75, 100, 125, 150	Widely available — historical originator brand. Well-established.
Thyrox	Macleods Pharmaceuticals	25, 50, 75, 100, 125, 150	Widely available
Thyrofit	Zydus Lifesciences	25, 50, 75, 100	Widely available
Lethyrox	Glenmark	25, 50, 100	Widely available
Levothyroxine (generic)	Multiple manufacturers	25, 50, 100	Widely available
Thyrozen (soft gel capsules)	Limited manufacturers	25, 50, 75, 100, 125, 150	Limited availability — major metros

Commonly Prescribed FDCs:

FDC	Availability	Notes
Levothyroxine + Liothyronine (T4 + T3)	Limited brands (e.g., Thyronorm Plus)	⚠️ NOT routinely recommended. Specialist use only.

CDSCO NSQ alerts: Levothyroxine has been subject to periodic quality concerns globally (narrow therapeutic index means small bioavailability differences matter). No major recent CDSCO NSQ alerts for established Indian brands at the time of this entry. Prescribers should verify current CDSCO alerts periodically.

PRICE RANGE (INR)

Prices as of June 2025. Verify current prices on NPPA/1mg/PharmEasy/Jan Aushadhi price lists as prices may change.

Strength	Per-Strip Price (various pack sizes)	Approx. Per-Tablet Price	NPPA Controlled
12.5 mcg (branded)	₹75–120 / 100 tablets	₹0.75–1.2	✅ Yes (NLEM listed)
25 mcg (branded)	₹90–140 / 100 tablets	₹0.9–1.4	✅ Yes
25 mcg (Jan Aushadhi)	~₹40–60 / 100 tablets	~₹0.4–0.6	✅ Yes
50 mcg (branded)	₹100–160 / 100 tablets	₹1.0–1.6	✅ Yes
50 mcg (Jan Aushadhi)	~₹50–80 / 100 tablets	~₹0.5–0.8	✅ Yes
75 mcg (branded)	₹120–180 / 100 tablets	₹1.2–1.8	✅ Yes
100 mcg (branded)	₹140–200 / 100 tablets	₹1.4–2.0	✅ Yes
100 mcg (Jan Aushadhi)	~₹60–100 / 100 tablets	~₹0.6–1.0	✅ Yes
125 mcg (branded)	₹160–220 / 100 tablets	₹1.6–2.2	✅ Yes
150 mcg (branded)	₹180–250 / 100 tablets	₹1.8–2.5	✅ Yes
200 mcg (branded)	₹220–300 / 100 tablets	₹2.2–3.0	✅ Yes

Estimated Monthly Cost at Usual Maintenance Dose (100 mcg/day):

Type	Monthly Cost (30 tablets)
Branded (Thyronorm/Eltroxin)	₹42–60/month
Jan Aushadhi	₹18–30/month

ℹ️ Levothyroxine is among the most affordable chronic medications available in India. A month’s treatment costs less than a single cup of coffee at a chain café. Cost should NEVER be a barrier to adherence.

NPPA ceiling price: ✅ Yes — NPPA price ceiling applicable for all NLEM-listed strengths.

PMBJP (Jan Aushadhi): Available for key strengths (25, 50, 100 mcg) at ~50–60% lower than branded prices.

CLINICAL PEARLS

💡 Empty stomach with water only — the Golden Rule. [Evidence-based] More levothyroxine treatment failures in India are caused by improper timing (taking with chai/coffee/milk, or concurrently with calcium/iron) than by incorrect dosing. Taking levothyroxine 30–60 minutes before breakfast with plain water alone improves absorption by 20–40% compared to taking with food/beverages. If a patient’s TSH is not normalising despite adequate dose, ASK: “What exactly do you take your tablet with, and when?” before increasing the dose.
💡 Calcium + Iron + Thyroid = the Indian triple challenge. [Practice-based] The most common co-prescription in Indian women: levothyroxine + calcium + iron. All three interact. Solution: Levothyroxine at 6 AM with water → breakfast at 7 AM → calcium with lunch (1 PM) → iron with dinner (8 PM). Write the timing ON THE PRESCRIPTION. Many Indian patients take all three together in the morning — this is a recipe for treatment failure.
💡 Do NOT start thyroid medicine based on one borderline TSH. [Evidence-based] A single TSH of 5.0–6.0 mIU/L does not equal hypothyroidism. TSH varies with time of day (higher in early morning), illness, medications (biotin, steroids), and assay variability. Always repeat TSH in 6–8 weeks before starting lifelong therapy. In India, “thyroid profile” screening has led to massive overdiagnosis and overtreatment of subclinical hypothyroidism — especially in asymptomatic young women.
💡 Brand switching matters for levothyroxine. [Evidence-based] Levothyroxine is a narrow therapeutic index drug. Different brands may have slightly different bioavailability due to differences in excipients, manufacturing processes, and dissolution characteristics. While generics are bioequivalent by regulatory standards, small differences can be clinically relevant for some patients. If a patient is stable on a brand, avoid switching unless necessary. If switching (e.g., for cost), recheck TSH at 6 weeks.
💡 Myth: “Thyroid medicine causes weight loss.” Fact: Levothyroxine restores normal metabolism — it is NOT a weight loss pill. [Practice-based] Euthyroid patients who take levothyroxine for weight loss risk iatrogenic thyrotoxicosis (atrial fibrillation, osteoporosis, anxiety, cardiac events). Levothyroxine should never be prescribed for obesity in euthyroid patients. In truly hypothyroid patients, weight loss after treatment is typically modest (2–5 kg of fluid loss) — the dramatic weight loss patients expect usually does not occur because thyroid hormone normalisation alone does not reverse lifestyle-related obesity. Set realistic expectations.
💡 Pregnancy + hypothyroidism = increase dose immediately, don’t wait for TSH. [Evidence-based] As soon as pregnancy is confirmed in a woman on levothyroxine, empirically increase the dose by 25–30% (or add 2 extra tablets per week). Do NOT wait for the next TSH result — fetal brain development in the first trimester depends on adequate maternal T4, and even a few weeks of relative undertreatment can affect neurodevelopment. Check TSH immediately after increasing and adjust further at 4 weeks.

VERSION

RxIndia v0.2 — 28 Jun 2025

REFERENCES

The following sources were consulted in preparing this monograph:

CDSCO Product Insert — Thyronorm (levothyroxine sodium), Abbott India Ltd, Indian product insert (most recent available revision).
CDSCO Product Insert — Eltroxin (levothyroxine sodium), Mylan/Viatris, Indian product insert.
Indian Pharmacopoeia 2022 — Levothyroxine Sodium monograph.
National List of Essential Medicines (NLEM) India, 2022 — Levothyroxine sodium listed under Section 18: Hormones, Other Endocrine Medicines and Contraceptives.
API Textbook of Medicine, 11th Edition — Chapters on Thyroid Disorders: Hypothyroidism, Myxedema Coma, Thyroid Cancer, Thyroid in Pregnancy.
Indian Thyroid Society (ITS) Guidelines — Management of Hypothyroidism; Subclinical Hypothyroidism; Thyroid Disorders in Pregnancy.
ISPAE (Indian Society for Paediatric and Adolescent Endocrinology) Guidelines — Congenital Hypothyroidism screening and management (2018).
IAP (Indian Academy of Pediatrics) Guidelines — Newborn Screening for Congenital Hypothyroidism.
RBSK (Rashtriya Bal Swasthya Karyakram) — NNSP Protocol — Newborn screening for congenital hypothyroidism.
ICMR Guidelines — National Iodine Deficiency Disorders Control Programme (NIDDCP).
ATA (American Thyroid Association) Guidelines — Management of Hypothyroidism (Jonklaas J, et al. Thyroid 2014;24(12):1670-1751). Referenced as supportive international guideline adopted in Indian practice.
ATA 2015 Guidelines — Management of Thyroid Nodules and Differentiated Thyroid Cancer (Haugen BR, et al. Thyroid 2016;26(1):1-133). Referenced for TSH suppression therapy.
ATA/Endocrine Society Guidelines — Thyroid Disease in Pregnancy and Postpartum (Alexander EK, et al. Thyroid 2017;27(3):315-389). Referenced for pregnancy management.
TRUST Trial — Stott DJ, et al. Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism. N Engl J Med 2017;376(26):2534-2544. Referenced for elderly SCH non-treatment.
Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 14th Edition — Chapter: Thyroid and Antithyroid Drugs. Pharmacokinetics, mechanism of action.
Harrison’s Principles of Internal Medicine, 21st Edition — Chapters on Disorders of the Thyroid Gland.
AIIMS Endocrinology Protocols — Myxedema coma management; Thyroid cancer follow-up.

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