Radioactive iodine for thyroid cancer
The thyroid gland absorbs and stores most of the iodine in your body. It gets iodine from certain foods and uses this to make essential thyroid hormones.
Radioactive iodine treatment is a type of radioisotope therapy. It uses a radioactive form of iodine called iodine 131 (I-131). The radioactive iodine circulates through your body in your bloodstream. The thyroid gland cells take up the radioactive iodine but it has little effect on other cells.
The thyroid cells take in the iodine and get a very high dose of radiation. This destroys the thyroid cells and any cancer cells.
You have radioactive iodine as a drink or capsule which you swallow. The capsule is about the size of a paracetamol capsule.
You won’t be able to eat or drink for a couple of hours afterwards so that your body can absorb the iodine. After that, you should drink plenty of fluids to flush the radioactive iodine out of your system. You can eat as normal.
The treatment makes you radioactive. So your sweat, urine and saliva will be radioactive for a few days. There are certain precautions that you and the staff need to follow. Try not to be alarmed by these. Your treatment contains a low dose of radiation that is necessary to treat your cancer.
A radiation monitor (Geiger counter) may be used to check your levels of radioactivity or test anything that is taken out of your room.
Your meals may be served on disposable plates with disposable cutlery. You put these in a special bin when you have finished with them.
The hospital staff ask you to flush the toilet more than once after you have used it and to shower each day.
Being in a room on your own (isolation) protects other people from radiation. Pregnant women and children are not allowed into your room. Other visitors may be able to stay for a short time when it is safe for them to do so.
The amount of time staff are allowed into your room is limited. They stay at a safe distance from you and can only stay in your room with you for as long as is necessary. This is because they will care for many people who have this treatment. So the amount of radiation they are exposed to has to be carefully controlled. It is important that you know that you are not at any risk from the radiation.
Being alone in a single room can feel lonely. Some people find it frightening. It can help to talk to the nurses about your worries. They can reassure you.
You may be able to take a few personal possessions into your room. The hospital staff will tell you if this is possible and what you can have with you. They may suggest not bringing too many items in and nothing of value. When you are ready to go home, you may need to leave some of your things behind until they don’t have any radiation on them.
Some hospital rooms will have a television and a phone. You could check before you go in to find out if this is the case.
Last reviewed: 15 Aug 2023
Next review due: 15 Aug 2026
You might need to have a low iodine diet for a few weeks before you have your treatment. Your thyroid stimulating hormone levels also need to be high before treatment.
Your healthcare team will tell you about any safety precautions you need to follow after your radioactive iodine treatment.
There are people who can help and things you can do to help cope with a diagnosis of thyroid cancer.
Doctors will arrange for you to have tests and scans at regular follow up appointments.
The thyroid is a small butterfly shaped gland that makes and releases hormones. It’s found at the front of your neck in the lowest part.

About Cancer generously supported by Dangoor Education since 2010. Learn more about Dangoor Education
Search our clinical trials database for all cancer trials and studies recruiting in the UK.
Meet and chat to other cancer people affected by cancer.
Questions about cancer? Call freephone 0808 800 40 40 from 9 to 5 - Monday to Friday. Alternatively, you can email us.