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Radioactive Iodine Treatment

(Radioiodine Treatment)

Pronounced: RAY-dee-oh-AK-tiv I-oh-dine



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.

The Thyroid Gland

Copyright © Nucleus Medical Media, Inc.


Reasons for Procedure    TOP

It may be done to treat:


Possible Complications    TOP

Possible side effects and complications of radioactive iodine therapy include:

  • Inflammation of the salivary glands causing painful cheeks and dry mouth
  • Metallic taste in the mouth
  • Dry mouth
  • Sore throat
  • Neck pain
  • Nausea or vomiting
  • Fatigue
  • Flushing
  • Tightness in throat
  • Abnormally high or abnormally low thyroid hormone levels

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    TOP

Prior to Procedure

  • If advised by your doctor, eat a special diet. Your doctor may want you on a special low iodine diet prior to the procedure. This may help your procedure to be more successful.
  • Talk to your doctor about your medications. Some thyroid hormone medications should be discontinued up to 4 weeks before the procedure. Other medications used to treat hyperthyroidism should be discontinued a minimum of 5-7 days before the procedure.
  • For 2 hours before the procedure, do not eat or drink anything. Water may be allowed.
  • If you are a woman of childbearing age, the doctor will do a pregnancy test.
  • A thyroid uptake and scan may be done before the treatment.

Description of 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.

How Long Will It Take?    TOP

At least an hour

Will It Hurt?    TOP

The treatment is painless.

Postoperative Care    TOP

Any radioactive iodine that is not taken up directly by the thyroid will be passed through the urine. Instructions may include:

  • Do not eat any solid foods for at least 2 hours after treatment. Drink a lot of clear liquids, such as water or juice.
  • For the first 8-12 hours following treatment, use the bathroom every hour. This will help flush the excess iodine from your body.
  • Limit your contact with others. Do not enter a room with any infants or children. Stay at least 3 feet away from other adults. Do not stay near any other adult for more than a few minutes. Do not share a bed with anyone for 48 hours following the treatment.
  • Do not share any food, drink, or dishes with anyone for the first week. Do not allow your saliva to come into contact with anyone. Avoid kissing and sexual contact.
  • Flush the toilet twice after use.
  • Wash hands often and thoroughly.
  • Resume normal thyroid medications 48 hours after the treatment.

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    TOP

Call your doctor if any of these occur:

  • Signs of infection, such as fever and chills
  • Nausea or vomiting
  • Excessive fatigue
  • Worsening pain or swelling in the neck
  • Passing little urine
  • Tightness in throat or trouble breathing
  • Facial numbness
  • Rapid pulse

If you think you have an emergency, call for emergency medical services right away.


American Thyroid Association

Hormone Health Network—Endocrine Society


Health Canada

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:
...(Click grey area to select URL)
Accessed November 28, 2017.

Radioiodine (I-131) therapy. Radiological Society of North America Radiology Info website. Available at:
...(Click grey area to select URL)
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

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