Treatment Overview

Radioactive iodine, given in a capsule or liquid form, is absorbed and concentrated by the thyroid gland . The treatment destroys thyroid tissue but does not harm other tissue in the body.

While radiation can cause thyroid cancer, treatment of hyperthyroidism with radioactive iodine does not increase your chances of getting thyroid cancer.

What To Expect

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}

• Keep your distance from other people, especially children and pregnant women.
• Do not sit next to someone in a motor vehicle for more than 1 hour.
• Avoid close contact, kissing, or sex.
• Sleep alone in a separate room.
• Use separate towels, washcloths, and sheets. Wash these and your personal clothing separately for 1 week.
• Flush the toilet twice after each use. Rinse the bathroom sink and tub thoroughly after you use them.

After treatment, you may have follow-up examinations every 4 to 6 weeks to check your thyroid hormone levels.

Why It Is Done

Radioactive iodine may be used to treat hyperthyroidism in people who have non-cancerous (benign) thyroid nodules that make too much thyroid hormone.

Radioactive iodine is also used if you have your thyroid removed (thyroidectomy) because of thyroid cancer. Radioactive iodine therapy destroys any remaining thyroid tissue or cancer cells that were not removed during surgery.

Learn more

How Well It Works

In almost all cases, your thyroid hormone levels will return to normal or below normal after radioactive iodine treatment. This may take 8 to 12 weeks or longer. If your thyroid hormone level does not go down after 6 months, you may need another dose of radioactive iodine.

If you have thyroid cancer and you are treated with radioactive iodine, it may take from several weeks to many months for your body to get rid of any remaining cancer cells.

Your thyroid nodule is unlikely to grow after being treated with radioactive iodine.

Risks

Some side effects from radioactive iodine treatment include:

• Metallic taste in your mouth.
• Dry mouth.
• Sore throat.
• Neck pain. Radioactive iodine treatment can make your neck swell up or hurt.
• Nausea or vomiting, which is usually mild.
• Constipation or diarrhea.
• Fatigue.
• Unusually low (hypothyroidism) or unusually high (hyperthyroidism) thyroid levels.

If you have Graves' ophthalmopathy, also called thyroid eye disease, it may get worse temporarily after radioactive iodine therapy.