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Radioiodine for thyroid cancer

Radioiodine mō te mate pukupuku repe tenga


Pregnant women shouldn't have radioiodine. If you have not gone through menopause, you should practise safe contraception for one month before treatment. Women will routinely have a pregnancy test before they're treated.

Breastfeeding women shouldn't have radioiodine. You should stop breastfeeding two months before radioiodine to make sure the radioactivity doesn't affect your breast tissue.

Men should avoid fathering a child and women should avoid pregnancy for six months after treatment. Radioiodine treatment doesn't affect fertility.

Doctors have recommended that you have radioiodine (also called radioactive iodine) to treat your thyroid cancer. This is done at Christchurch Hospital Molecular Imaging and Therapy. This page has information about how radioiodine works, side effects and any precautions you need to take.

How the radioiodine works

Radioiodine destroys your thyroid cells. You're usually given it as a capsule. Some people need to take it again in six to 12 months.

Radioiodine has been used since the 1940s and is now an essential part of treating thyroid cancer.

Your doctor will decide how much radioiodine you need. It will depend on how much of your thyroid gland is left after surgery and the type of cancer you have.

Side effects

The iodine has no taste. Sometimes people feel a bit sick, and sometimes they have a sore throat for up to a week after treatment. Occasionally, they develop a dry mouth because they make less saliva after radioiodine treatment.

Radioiodine is generally very safe. Very high doses can slightly increase your risk of developing a different cancer. Most people are given a relatively low dose, which is not thought to cause cancer.

Radioiodine effect on children

There is no evidence that children are affected by their parent's treatment. But we still recommend that you reduce your children's radiation exposure to a minimum.

The doctor who prescribes the radioiodine will tell you how long your thyroid will be radioactive after your treatment. During this time, usually seven to 10 days, you shouldn't have children closer than two arms' length for more than a few minutes at a time. But you do not need to stop essential contact such as cuddles, dressing or soothing. It's best to avoid kisses for 48 hours after the radioiodine.

Precautions after treatment

For about one week after the treatment, it's best that you sleep in a separate bed from your partner. Your doctor will talk to you about this.

Whether you should stay off work after your treatment depends on your job. If you work with children or pregnant women, you should take some time off work. If you work with adults, keeping them at two arms' length from you for a few days may be all you need to do. The doctor will talk about this with you.

It's best that you go home by car after your treatment. If you have to take public transport, make sure that you only sit with adults. Move to another seat if a child or pregnant woman sits within two arms' length of you.

Your thyroid takes up much of the radioiodine and you remove the rest through your urine and bowel movements (poo). During the first three days after your radioiodine treatment, flush the toilet immediately. Then flush the toilet a second time and wipe up any spilled urine with a tissue and flush it away. Always wash your hands well afterwards. It's best for men to use the toilet sitting down.

There will also be radioactivity in other body fluids, including saliva, sweat and mucus from your nose. Use tissues to wipe your nose and make sure you put them in the rubbish – preferably not in your living areas. Do not leave tissues lying around. Avoid cooking food for others and use your own crockery and cutlery for several days after your treatment.

If you have any more questions, ask your doctor.

Written by the Department of Endocrinology, Christchurch Hospital. Adapted by HealthInfo clinical advisers. Last reviewed July 2023.


See also:

Thyroid cancer

Page reference: 70796

Review key: HITHY-49064