Levothyroxine

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).

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

Route(s)

Formulations Available in India

Clinically Relevant FDCs Available in India:

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PHARMACOKINETICS

Population PK Notes

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ADULT INDICATIONS + DOSING

Primary Indications (Approved / Standard in India)

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1. Primary Hypothyroidism (Overt)

1. 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]
2. 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.
3. 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).
4. 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.
5. 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.
6. Mandatory baseline investigations:
7. • 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
8. 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.
9. 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.
10. ⚠️ 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.
11. Dose adjustment scenarios:
12. • 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

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2. Subclinical Hypothyroidism (SCH)

Mandatory Clinical Notes:

1. 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.
2. 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.
3. NLEM India status: ✅ Yes (the drug is listed; the indication is managed per clinical judgment).
4. 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.
5. Treatment failure: Persistent symptoms despite normalised TSH → investigate other causes (depression, anaemia, sleep apnoea, vitamin D deficiency, perimenopause).
6. Mandatory baseline: TSH (repeated on two occasions 6–8 weeks apart), fT4, anti-TPO antibodies.
7. Specialist vs primary care: Can be managed in primary care. Specialist referral for uncertain cases, children, elderly >70 years.
8. Indian guideline source: Indian Thyroid Society position statement on subclinical hypothyroidism. API Textbook. ATA Guidelines (supportive).
9. 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).
10. Dose adjustment: Lower starting doses (25 mcg) sufficient for SCH. Target TSH need not be <2.5 mIU/L except in pregnancy.

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

Mandatory Clinical Notes:

1. 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]
2. 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.
3. NLEM India status: ✅ Yes.
4. Time to response: TSH suppression achieved in 4–6 weeks. Adjust dose based on TSH levels.
5. Treatment failure: TSH fails to suppress despite high doses → investigate adherence, absorption issues. Consider thyroglobulin levels for disease monitoring.
6. Mandatory baseline: TSH, fT4, fT3, thyroglobulin (Tg), anti-Tg antibodies, calcium/PTH (post-thyroidectomy hypoparathyroidism), neck ultrasound. ECG in elderly.
7. Specialist only: ⚠️ TSH suppression therapy must be initiated and monitored by an endocrinologist or oncologist. Primary care should not independently adjust suppressive doses.
8. Indian guideline source: ATA 2015 DTC Guidelines (internationally adopted in Indian practice). AIIMS Endocrine Surgery protocols. API Textbook.
9. ⚠️ 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.
10. Dose adjustment: Regular TSH monitoring (every 3 months initially, then 6 monthly when stable). Adjust in 12.5–25 mcg increments.

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4. Secondary (Central) Hypothyroidism

Mandatory Clinical Notes:

1. When to prefer: Only option for central hypothyroidism (pituitary/hypothalamic disease). [Evidence-based]
2. 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.
3. NLEM India status: ✅ Yes.
4. Time to response: Same as primary hypothyroidism.
5. Treatment failure: fT4 does not rise despite adequate doses → investigate adherence, malabsorption.
6. Mandatory baseline: Full pituitary hormone panel (ACTH-cortisol axis is CRITICAL), MRI pituitary.
7. Specialist only: Yes — Endocrinology.
8. Indian guideline source: API Textbook. Endocrine Society clinical practice guidelines.
9. ⚠️ Key safety warning: Adrenal crisis risk as stated above. This is one of the most dangerous prescribing errors in endocrinology.
10. Dose adjustment: Guided by fT4, not TSH.

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5. Myxedema Coma (IV Route)

Mandatory Clinical Notes:

1. When to prefer IV: Always, when available. IV levothyroxine bypasses unpredictable GI absorption in the critically ill patient.
2. 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.
3. NLEM India status: ✅ Yes (injection formulation listed).
4. 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).
5. Treatment failure: Mortality remains high despite treatment. Poor prognostic factors: advanced age, bradycardia, hypothermia <32°C, high APACHE score.
6. Mandatory baseline:
7. • 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.
8. Specialist only: Yes — ICU/Endocrinology/Critical Care.
9. Indian guideline source: API Textbook — Myxedema Coma management. AIIMS Endocrinology protocol. Endocrine Society guidelines.
10. ⚠️ 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.
11. Dose adjustment: Lower loading dose in cardiac disease. Adjust maintenance based on clinical response and fT4 levels.

• 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.

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

Mandatory Clinical Notes:

1. 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]
2. 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.
3. NLEM India status: ✅ Yes.
4. Time to response: Goitre reduction (if any) over 6–12 months.
5. Treatment failure: No reduction in goitre size after 12 months → discontinue levothyroxine. Consider surgery for symptomatic goitre.
6. Mandatory baseline: TSH, fT4, thyroid ultrasound, anti-TPO antibodies. FNAC if nodule present.
7. Specialist vs primary care: Specialist initiation recommended.
8. Indian guideline source: API Textbook. Indian Thyroid Society.
9. Key safety warning: Risk of iatrogenic thyrotoxicosis with TSH suppression.
10. Dose adjustment: Target only mild TSH suppression (0.3–0.5), not full suppression.

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

1. Depression Augmentation — OFF-LABEL

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

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PAEDIATRIC DOSING (Specialist Only)

• ⚠️ 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.

Neonatal Congenital Hypothyroidism (NICU/Neonatology Supervision)

• 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.

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Primary Indications — Paediatric (Approved / Standard in India)

1. Congenital Hypothyroidism

Clinical Notes:

1. When to prefer: Levothyroxine is the only treatment for congenital hypothyroidism. No alternatives. [Evidence-based]
2. When NOT to use: No contraindication in congenital hypothyroidism — treatment is mandatory.
3. NLEM India status: ✅ Yes.
4. Time to response: fT4 normalises in 1–2 weeks. TSH normalises in 2–4 weeks.
5. Treatment failure: Persistent high TSH → check adherence (most common issue), dosing adequacy, absorption (soy formula?).
6. 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.
7. Specialist: Paediatric Endocrinology. If unavailable, neonatologist or paediatrician with guidance from endocrinology.
8. Indian guideline source: IAP Guidelines on Newborn Screening and Congenital Hypothyroidism (2018). Indian Society for Paediatric and Adolescent Endocrinology (ISPAE) Guidelines. RBSK-NNSP protocol.
9. ⚠️ 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.
10. Dose adjustment: Frequent dose adjustments needed in first 3 years due to rapid growth. Weight-based dosing recalculated at each visit.

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

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).

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

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MISSED DOSE / DELAYED DOSE GUIDANCE

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RECONSTITUTION / ADMINISTRATION QUICK REFERENCE

Oral Administration

IV Administration (Myxedema Coma — ICU Only)

Stability After Reconstitution

Multi-Dose Vial Handling

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)

• 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

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RENAL ADJUSTMENT

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HEPATIC ADJUSTMENT

• 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.

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CONTRAINDICATIONS

• 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).

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CAUTIONS

⚠️ High-Priority Cautions

Standard Cautions

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PREGNANCY

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.

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LACTATION

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ELDERLY

Extra Risks Specific to Elderly:

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.

• ⚠️ 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.

• 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.

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MAJOR DRUG INTERACTIONS

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MODERATE DRUG INTERACTIONS

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COMMON ADVERSE EFFECTS

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SERIOUS ADVERSE EFFECTS

• 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

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MONITORING REQUIREMENTS

Baseline (Before Starting)

After Initiation / Dose Change

Long-Term / Maintenance

Therapeutic Drug Monitoring (TDM)

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.

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PATIENT COUNSELLING

• ”⚠️ 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).“

• 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."

• 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)"

• ”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“

• 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

• 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.

• 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.“

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BRANDS AVAILABLE IN INDIA

Commonly Prescribed FDCs:

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PRICE RANGE (INR)

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CLINICAL PEARLS

1. 💡 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.
2. 💡 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.
3. 💡 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.
4. 💡 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.
5. 💡 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.
6. 💡 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.

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REFERENCES

1. CDSCO Product Insert — Thyronorm (levothyroxine sodium), Abbott India Ltd, Indian product insert (most recent available revision).
2. CDSCO Product Insert — Eltroxin (levothyroxine sodium), Mylan/Viatris, Indian product insert.
3. Indian Pharmacopoeia 2022 — Levothyroxine Sodium monograph.
4. National List of Essential Medicines (NLEM) India, 2022 — Levothyroxine sodium listed under Section 18: Hormones, Other Endocrine Medicines and Contraceptives.
5. API Textbook of Medicine, 11th Edition — Chapters on Thyroid Disorders: Hypothyroidism, Myxedema Coma, Thyroid Cancer, Thyroid in Pregnancy.
6. Indian Thyroid Society (ITS) Guidelines — Management of Hypothyroidism; Subclinical Hypothyroidism; Thyroid Disorders in Pregnancy.
7. ISPAE (Indian Society for Paediatric and Adolescent Endocrinology) Guidelines — Congenital Hypothyroidism screening and management (2018).
8. IAP (Indian Academy of Pediatrics) Guidelines — Newborn Screening for Congenital Hypothyroidism.
9. RBSK (Rashtriya Bal Swasthya Karyakram) — NNSP Protocol — Newborn screening for congenital hypothyroidism.
10. ICMR Guidelines — National Iodine Deficiency Disorders Control Programme (NIDDCP).
11. 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.
12. 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.
13. ATA/Endocrine Society Guidelines — Thyroid Disease in Pregnancy and Postpartum (Alexander EK, et al. Thyroid 2017;27(3):315-389). Referenced for pregnancy management.
14. 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.
15. Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 14th Edition — Chapter: Thyroid and Antithyroid Drugs. Pharmacokinetics, mechanism of action.
16. Harrison’s Principles of Internal Medicine, 21st Edition — Chapters on Disorders of the Thyroid Gland.
17. AIIMS Endocrinology Protocols — Myxedema coma management; Thyroid cancer follow-up.