Content overview

What is radioactive iodine?

How is RAI treatment given?

What happens after RAI treatment?

For which people is RAI not a suitable treatment?

Further information 

What is radioactive iodine?

Radioactive iodine (RAI) has been used to treat overactive thyroid disorders (hyperthyroidism) since the early 1940s. It is a safe and very effective treatment and is now being offered as first-line definitive treatment rather than surgery. RAI is taken up by the thyroid, and destroys the cells in the thyroid gland. This reduces the amount of thyroxine made by the thyroid gland and may also reduce the size of the gland.

How is RAI treatment given?

The treatment is taken either as a simple capsule swallowed with mouthfuls of water, or as a drink. The gland has to be working when this treatment is taken, so antithyroid tablets should be stopped usually at least one week before the treatment is given and not taken for at least one week afterwards. You will be given instructions on when to stop the tablets.

What happens after RAI treatment?

After treatment, and depending on the amount of daily contact you have with others, you may be asked to avoid contact with other people for a short time. In particular you should avoid close contact with babies, children under five years and pregnant women. As a general rule you should keep at arm’s length for two to three weeks, but the length of time depends on the dose used and the people you will be in contact with. There is no reason to worry about the exposure to a pet.

Women should avoid getting pregnant for at least six months after treatment and men should not father a child for at least four months.

For which people is RAI not a suitable treatment?

RAI is not suitable for women who are pregnant or breastfeeding. It is also not suitable if your overactive thyroid is causing eye problems as the treatment may worsen thyroid eye disease.

Further information

Read our guide to treatment of an overactive thyroid with RAI

Radioactive iodine treatment for hyperthyroidism

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