Radioactive Iodine Treatment
Pronounced: RAY-dee-oh-AK-tiv I-oh-dine
by Diana Kohnle
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. The radioactivity is not spread to other parts of the body.
Reasons for Procedure
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.
What to Expect
Prior to Procedure
Description of the Procedure
You will be given some tablets or liquids that contain radioactive iodine. You will swallow the tablets. The iodine will be naturally taken up by the thyroid.
How Long Will It Take?
At least an hour
Will It Hurt?
The treatment is painless.
Any radioactive iodine that is not taken up directly by the thyroid will be passed through the urine. Be sure to follow your doctor's instructions. This 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 will be scheduled 4-6 weeks after treatment. Radioactive active 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
Call your doctor if any of these occur:
If you think you have an emergency, call for medical help right away.
American Association of Clinical Endocrinologists
Thyroid Foundation of Canada
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. The Endocrine Society Hormone Health Network website. Available at:
Radioiodine (I-131) therapy. Radiological Society of North America Radiology Info website. Available at:
Rivkees SA, Dinauer C: An optimal treatment for pediatric Graves’ disease is radioiodine. J Clin Endocrinol Metab. 2007; 92:797-800.
Last reviewed November 2013 by Kim Carmichael, MD