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Treating an overactive thyroid (hyperthyroidism)

The treatment options for an overactive thyroid (hyperthyroidism) include medicines, radioactive iodine and surgery. The treatment you'll need depends on the cause of your overactive thyroid and how well it responds to the treatment.

You may also need treatment if you have Graves' eye disease, which affects about one in 20 people who have Graves' disease. If you're experiencing irritation and redness, bulging eyes and double vision, you may need to see an ophthalmologist (specialist eye doctor). Treatment may include drops, medicines and rarely surgery.

Medicines for an overactive thyroid

woman taking tabletAnti‑thyroid medications like carbimazole block your thyroid producing thyroxine. They take four to six weeks to bring your levels back to normal.

You often start on a high dose, which can be reduced once your thyroxine levels have dropped. If the medicine works and doesn't cause side effects, you'll usually keep taking it for six to 12 months.

In cases where Graves' disease is causing an overactive thyroid, this will permanently cure about half of those treated. The rest will have their overactive thyroid problem come back and will need more treatment.

Most people don't get side effects with these medicines, but they can cause stomach upset, rash and joint pains. Very rarely, you can get a low white blood cell count (fewer white blood cells in your blood). These cells help your body fight infection. If you have a high temperature, sore throat or mouth ulcer, stop taking your thyroid medicine and see a doctor urgently to have a blood test.

You might also get a medicine called a beta blocker, like propranolol. This doesn't affect your thyroid but helps with some of the symptoms, such as the shakes (tremor), racing heart (palpitations), and nervousness.

Radioiodine treatment

In radioiodine treatment you drink or take a capsule of iodine that has been made radioactive. This destroys your thyroid cells, causing your thyroid to shrink. It takes several weeks to be effective and is successful in most people.

This is a very safe and effective treatment. The radiation dose you receive is very small and isn't enough to cause cancer later in life.

You'll need to take precautions for two to three weeks after your treatment, while your body clears the low‑dose radiation. This includes limiting close contact with children and pregnant women. Your health professional will advise you to avoid pregnancy for several months after treatment.

The main side effect of treatment is that your thyroid may become underactive (hypothyroidism). You'll have blood tests to check for this and it's easily treated with thyroid tablets.


Sometimes people need surgery to remove part or all of their overactive thyroid. Surgery is particularly useful if you have a very large thyroid or if other treatments haven't worked.

Thyroid surgery is generally very safe but can have some side effects, such as affecting your calcium balance or damaging your vocal cords.

After surgery, your thyroid may become underactive (hypothyroidism). You'll have blood tests to check for this and it's easily treated with thyroid tablets.

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Written by HealthInfo clinical advisers. Last reviewed May 2020.


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