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Radioiodine is a form of iodine that is radioactive. It is given as a tablet or capsule and is used to treat thyroid glands that are over-active or very large. Most of the radioactivity is taken up by the over-active thyroid, where it damages the gland, slowing down the production of thyroid hormone and causing it to get smaller in size. The rest of the radioiodine is passed harmlessly out of the body in the urine. Radioiodine is a permanent, painless and effective treatment for thyroid-activity which avoids the need for surgery.
The main side effect is an under active thyroid gland which happens eventually in many people.
Usually one treatment with radioiodine is enough, but some patients require two or more treatments. You will need to see your specialist at the hospital and your GP after the treatment for regular checks.
Radioiodine treatment is safe and effective and has been used for many decades. Studies have shown that radioiodine treatment is not associated with a higher risk of any cancer compared to other ways of treating an overactive thyroid.
It is NOT safe for pregnant or breastfeeding women to be given radioactive treatment, because the radioactive iodine would damage the baby’s thyroid.
Women should avoid pregnancy for 6 months following treatment. Men should avoid fathering a child for 4 months.
Radioiodine patients give off invisible radiation, similar to x-rays. At a distance of 2 metres or more, the radiation is extremely weak. Nearer to a patient it is stronger. The radiation given off is strongest immediately after the treatment, and becomes a little weaker each day. After a period of between two and four weeks, the radiation hazard will become so small that it can be completely disregarded.
You will need to follow certain precautions for the safety of other people. Precautions will apply for between two and four weeks, depending on the size of your treatment-dose, and on your particular home and work situation.
On your first visit to the Nuclear Medicine Department, a specialist doctor will discuss your situation and advise you on precautions. You should tell the doctor if any of the following apply:
In this hospital, radioiodine is given as a capsule and the treatment is painless. You will first be seen by a specialist Nuclear Medicine doctor, and the treatment will follow at a later date.
At your consultation with the Nuclear Medicine doctor:
On your second visit to the Nuclear Medicine Department you will be seen by a radiation specialist:
The response to treatment varies from person to person. Follow-up visits with blood tests are ESSENTIAL, to ensure that your continuing care is right for your individual response. Your first follow-up visit will be about 6 weeks after the treatment.
Your doctor should discuss the reasons for recommending a particular treatment with you.
Patient self help groups and further information:
There is a short video about radioactive iodine treatment available on our website.
This information is intended for patients receiving care in Brighton & Hove or Haywards Heath.
This information is for guidance purposes only and is in no way intended to replace professional clinical advice by a qualified practitioner.
Publication Date: July 2021
Review Date: April 2024