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Radioactive iodine is a medicine that you take one time. After you swallow it, it is taken up by your thyroid gland. Depending on the dosage used, the radioactivity in the iodine destroys most or all of the tissue in your thyroid gland, but it does not harm any other parts of your body.
While radiation can cause thyroid cancer, treatment of hyperthyroidism with radioactive iodine does not increase your chances of getting thyroid cancer.
Radioactive iodine treatment has been safely used on millions of people for more than 60 years.
Most people don't feel different after treatment. But a few people may have nausea.
Within a few days after treatment, the radioactive iodine will leave your body in your urine and saliva. How long it takes will depend on your age and on the dose you received. Young people get rid of radioactive iodine faster than older adults. Drink plenty of fluids during this time to help your body get rid of the radioactivity.
Your doctor will give you written instructions. To avoid exposing other people to radioactivity, it is important to follow these carefully. He or she will instruct you on how far to stay away from people, how long you need to sleep alone, and other ways to stay safe. You will be told to avoid close contact, kissing, sex, and sharing cups, dishes, or utensils.
Some general recommendations include:footnote 1
After treatment, you may have follow-up examinations every 4 to 6 weeks to check your thyroid hormone levels.
Radioactive iodine has the best chance of permanently curing hyperthyroidism. Doctors often use it if your hyperthyroidism comes back after you have been treated with antithyroid medicine. It can also be used if your hyperthyroidism comes back after you have surgery to remove part of your thyroid gland.
For most people, one dose of radioactive iodine treatment will cure hyperthyroidism. Usually, thyroid hormone levels return to normal in 8 to 12 weeks. In rare cases, the person needs a second or third dose of radioactive iodine.
Some side effects from radioactive iodine treatment include:
If you have Graves' ophthalmopathy, also called thyroid eye disease, it may get worse temporarily after radioactive iodine therapy.
CitationsSisson JC, et al. (2011). Radiation safety in the treatment of patients with thyroid diseases by radioiodine 131I: Practice recommendations of the American Thyroid Association. From the American Thyroid Association Taskforce on Radioiodine Safety. Thyroid, 21(4): 335–346.
Current as of: March 1, 2023
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Kathleen Romito MD - Family Medicine & David C.W. Lau MD, PhD, FRCPC - Endocrinology
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