Radioactive iodine treatment is used to treat certain thyroid diseases and thyroid cancer. The procedure is done with a radioactive form of the element iodine. Radioactive iodine is taken up by the thyroid gland. There, it treats thyroid disease by destroying the cells. Though the radioactivity has minimal spread to other parts of the body, it will appear in the urine.
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It may be done to treat:
Possible side effects and complications of radioactive iodine therapy include:
Pregnant women are at an increased risk of complications. The procedure may be harmful to the fetus. It should not be done in pregnant women. Nursing mothers should stop breastfeeding for at least a week after the procedure.
You will be given some tablets or liquids that contain radioactive iodine. After the iodine is swallowed, it will be taken up by the thyroid.
At least an hour
The treatment is painless.
Any radioactive iodine that is not taken up directly by the thyroid will be passed through the urine. Instructions may include:
The majority of people who undergo the treatment for hyperthyroidism will have their thyroid levels return to normal within 8-12 weeks. However, in a small number of people, a second dose of radioactive iodine treatment is needed.
A follow-up visit with your doctor may be scheduled 4-6 weeks after treatment. Radioactive iodine treatment can cause hypothyroidism (low thyroid function). This can occur at any time after treatment. It may be temporary or permanent. Your doctor will need to check your thyroid status every few months until levels are stable.
Call your doctor if any of these occur:
If you think you have an emergency, call for emergency medical services right away.
American Thyroid Association
Hormone Health Network—Endocrine Society
Thyroid Foundation of Canada
Pluijmen MJ, Eustatia-Rutten C, Goslings BM, et al. Effects of low-iodide diet on postsurgical radioiodide ablation therapy in patients with differentiated thyroid carcinoma. Clin Endocrinol (Oxf). 2003;58(4):428-435.
Radioactive iodine for hyperthyroidism. Endocrine Society Hormone Health Network website. Available at: http://www.hormone.org/questions-and-answers/2012/radioactive-iodine-treatment-for-hyperthyroidism. Accessed November 28, 2017.
Radioiodine (I-131) therapy. Radiological Society of North America Radiology Info website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=radioiodine. Updated March 17, 2016. Accessed November 28, 2017.
Rivkees SA, Dinauer C. An optimal treatment for pediatric Graves’ disease is radioiodine. J Clin Endocrinol Metab. 2007;92(3):797-800.
Last reviewed November 2018 by EBSCO Medical Review Board James Cornell, MD Last Updated: 12/14/2015