Levothyroxine

Thyroid hormone
PRESCRIPTION ONLY IN INDIA

Levothyroxine is a thyroid hormone found in 3 medicines sold in India, such as Thyronorm, Eltroxin, Thyrox. Below: what it is for, how it works, how to take it, side effects, interactions and pregnancy advice.

Also called: thyroxine, t4

What it is used for

Replaces thyroid hormone in an underactive thyroid (hypothyroidism).

How it works

A synthetic copy of the thyroid hormone T4, replacing what an underactive thyroid cannot make.

How to take it

Take once a day on an empty stomach with water, 30 to 60 minutes before breakfast and tea or coffee, at the same time daily. Blood tests (TSH) guide the dose; it takes 6 weeks to settle after a change.

Common side effects

Usually none at the right dose. Too much: palpitations, sweating, weight loss, anxiety, trouble sleeping

Get medical help straight away if

Chest pain, very fast or irregular heartbeat

Be careful

Take on an empty stomach, 30 to 60 minutes before breakfast; keep away from calcium and iron.

Other medicines and interactions

Iron, calcium, antacids, PPIs, soy and fibre supplements reduce absorption; separate by 4 hours. Can change warfarin and diabetes medicine needs.

Pregnancy and breastfeeding

Essential to continue in pregnancy; the dose often needs to go up early, so tell your doctor as soon as you are pregnant. Safe while breastfeeding.

Brands of Levothyroxine (3)

EltroxinThyronormThyrox

Common questions

What is Levothyroxine used for?

Replaces thyroid hormone in an underactive thyroid (hypothyroidism).

How does Levothyroxine work?

A synthetic copy of the thyroid hormone T4, replacing what an underactive thyroid cannot make.

How should I take Levothyroxine?

Take once a day on an empty stomach with water, 30 to 60 minutes before breakfast and tea or coffee, at the same time daily. Blood tests (TSH) guide the dose; it takes 6 weeks to settle after a change.

What are the side effects of Levothyroxine?

Common: Usually none at the right dose. Too much: palpitations, sweating, weight loss, anxiety, trouble sleeping. Get help straight away for: Chest pain, very fast or irregular heartbeat.

Does Levothyroxine interact with other medicines?

Iron, calcium, antacids, PPIs, soy and fibre supplements reduce absorption; separate by 4 hours. Can change warfarin and diabetes medicine needs.

Is Levothyroxine safe in pregnancy and breastfeeding?

Essential to continue in pregnancy; the dose often needs to go up early, so tell your doctor as soon as you are pregnant. Safe while breastfeeding.

Does Levothyroxine need a prescription in India?

Yes. In India it is a prescription (Schedule H) medicine, so a pharmacist should sell it only with a doctor's prescription.

Which brands contain Levothyroxine?

Eltroxin, Thyronorm, Thyrox.

Sources and further reading

NHS (UK National Health Service) and MedlinePlus (US National Library of Medicine) are free, reviewed medicine guides. Brand names and doses there may differ from India.

Last reviewed 31 October 2026. Written by Satya Babu from standard prescribing information.

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For information only, not medical advice. This page is a plain-language summary written from standard prescribing information and the public guides linked below. Brands sometimes change their formula, so always check the composition printed on the pack. Doses here are typical adult doses; yours may differ. Do not start, stop or change a medicine without your doctor or pharmacist, and keep all medicines away from children. In an emergency, call 112 (India) or your local emergency number.