What it is used for
- Underactive thyroid (hypothyroidism)
- Thyroid hormone replacement after thyroid surgery or radioactive iodine
- Certain types of goitre and thyroid cancer follow-up (when prescribed)
How it works
It is a synthetic version of thyroxine, the hormone your thyroid gland normally makes. It replaces missing thyroid hormone so your body's metabolism works normally.
How it is taken
Usually taken as a once-daily tablet, and also available as a liquid or capsule. It is generally taken on an empty stomach with water, often before food. Take it exactly as your doctor or pharmacist directs, at the same time each day, and do not change the brand or dose without advice, as regular blood tests guide adjustments.
No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.
Common side effects
- Usually none when the dose is correct
- Symptoms of too much hormone if the dose is too high, such as palpitations, tremor, sweating, or weight loss
- Symptoms of too little if the dose is too low, such as tiredness, weight gain, or feeling cold
Serious effects — get help
- Chest pain
- Fast or irregular heartbeat
- Severe shortness of breath
- Signs of a serious allergic reaction
If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.
Interactions to watch
- Calcium and iron supplements (separate by several hours)
- Some indigestion remedies and antacids
- Some medicines for osteoporosis, cholesterol, and seizures
- Certain diabetes medicines may need dose review
- Soya, coffee, and high-fibre foods taken too close to the dose can reduce absorption
Who should take care
- Tell your clinician if you have heart disease, as doses are usually started low and increased slowly
- Dose needs often change during pregnancy, so tell your clinician promptly if you are or might be pregnant
- Take it consistently in relation to food and other medicines
- Do not stop suddenly without advice