If you’ve been told that you need to have treatment with radioactive iodine, knowing more about what to expect can help. This section tells you what’s likely to happen before, during and after the treatment. Your doctors and nurses will also explain things to you and answer your questions.
how does it work?
Radioactive iodine treatment is a way of giving you radiotherapy from the inside. It targets thyroid cells and thyroid cancer cells.
You’re given a radioactive form of iodine called iodine-131. Your thyroid cells and any cancer cells in your body absorb the radioactive iodine and are destroyed by radiation.
Other parts of the body aren’t usually affected by this treatment, because other cells don’t absorb iodine.
Radioactive iodine treatment is only used to treat papillary or follicular thyroid cancer.
how is it given?
It’s usually given as a capsule or as a drink.
preparing for treatment
If you’re taking thyroid hormones, you’ll be asked to stop taking them for 2-4 weeks before the treatment. This is because radioactive iodine works better without these hormones. Some people aren’t started on thyroid hormones until after surgery and radioactive iodine treatment anyway.
For about two weeks before treatment, you eat a low iodine diet. (You’ll be told which foods to eat and what to avoid.) Because you’re not eating any iodine, your body will use up its iodine stores. Then, when you’re given the radioactive iodine, the cancer cells will soak it up because the amount of iodine in your body is low.
what happens during treatment?
The treatment makes you slightly radioactive for about 4-5 days. Your body gets rid of the radioactivity through your urine (pee), sweat and saliva. You’ll usually be kept in hospital during that time and looked after in a side room on the ward, either on your own or with someone else having the same treatment.
The amount of contact you can have with your friends, family and the nurses will be limited, so that they don’t get radiation they don’t need. Anyone younger than 18 usually won’t be allowed to visit you. Take in plenty of books, magazines, computer games and your MP3 player to help pass the time. Anything that comes back out of your room will be checked for radiation levels. Sometimes your things may have to be kept on the ward for a few days or weeks (up to six weeks) if the radiation levels are high. But they’ll be returned to you when they’re safe again.
what happens after treatment?
Once your radiation levels are safe, you’ll be allowed home. You’ll also be able to start eating your usual foods again. Check with the staff about what you can and can’t do when you get home. There may be some precautions to take for a few days.
Fertility in girls and guys isn’t usually affected by the treatment. But occasionally guys who have more than two doses of radioactive iodine can be less fertile afterwards. If the doctors think you might be affected, they’ll talk to you about storing sperm before your treatment starts.
It’s important not to become pregnant or get someone else pregnant during treatment, and for six months afterwards. This is in case the treatment affects a baby conceived within this time.
There's more information about this in our fertility section.
