Carbimazole reduces the amount of thyroid hormone the thyroid makes. It works well, and it has one warning that everyone taking it must know, because acting on it quickly can be life-saving.
Usually once or twice daily, with or without food, at the same time each day.
It takes several weeks to bring thyroid levels down, so symptoms improve gradually. A beta blocker such as propranolol is often given alongside at first to control palpitations and tremor.
Blood tests check thyroid function regularly, and the dose is adjusted from those. Treatment often runs 12 to 18 months.
Do not stop without medical advice — symptoms usually return.
Common: nausea, headache, joint or muscle aches, rash and itching. Mild rash is common and not usually a reason to stop, but report it.
Also report yellowing of the eyes or skin, severe stomach pain, or worsening symptoms.
Carbimazole in pregnancy carries a risk of birth defects, particularly in the first trimester. Effective contraception is advised, and if you are planning a pregnancy or become pregnant, contact your specialist promptly — propylthiouracil is often used instead in early pregnancy. Do not simply stop.
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