What It Is Used For
Levothyroxine replaces thyroid hormone when the thyroid gland does not make enough (hypothyroidism). It is also used after thyroid surgery and in some types of goitre and thyroid cancer.
How to Take It
Take it once a day on an empty stomach, with a glass of water, 30 to 60 minutes before breakfast, at the same time each day. The dose is set for each person from blood tests (TSH). Adults often start on 50 mcg to 100 mcg a day; older people and people with heart disease usually start lower, such as 12.5 mcg to 25 mcg. Most people need it for life, so do not stop unless your doctor tells you to. It takes several weeks to feel the full effect.
Who Should Not Take It
Do not take it if you are allergic to levothyroxine, have an overactive thyroid that is not treated, untreated adrenal gland problems, or have just had a heart attack. It must not be used to lose weight.
Side Effects
At the right dose there are usually no side effects. A dose that is too high can cause a fast or pounding heartbeat, shaking, sweating, feeling hot, diarrhoea, weight loss, trouble sleeping or anxiety. Get medical help straight away for chest pain or a very fast or irregular heartbeat.
Precautions
Tell your doctor if you have heart disease, high blood pressure, diabetes (your diabetes medicine may need adjusting) or weak bones. You will need regular blood tests to check the dose.
Pregnancy and Breastfeeding
It is safe and important to keep taking it during pregnancy and breastfeeding. Tell your doctor as soon as you know you are pregnant, because the dose often needs to be increased.
Interactions
Calcium, iron, antacids, some stomach medicines (omeprazole and similar), cholestyramine and orlistat can reduce how much is absorbed, so take them at least 4 hours apart. It can increase the effect of warfarin. Carbamazepine, phenytoin and rifampicin can lower its effect.
Storage
Store below 25°C in the original pack, protected from light and moisture, out of the reach of children.