Treatment Overview

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.

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 exams every 4 to 6 weeks to check your thyroid hormone levels.

Why It Is Done

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.

How Well It Works

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.

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.