What is radioactive iodine treatment?

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Radioactive iodine 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.

Radioactive iodine therapy

Radioactive iodine therapy is used to destroy thyroid cells.

Radioactive iodine therapy can be used for thyroid cancer to kill cancer cells that remain after surgery has been done to remove the thyroid gland. It may also be used to treat an overactive thyroid gland (hyperthyroidism).

Radioactive iodine is usually given as a liquid or capsule that is swallowed.

How can you care for yourself after radioactive iodine treatment?

General recommendations

  • For a period of time, you will need to keep your distance from other people, especially young children and pregnant women.
  • Avoid close contact, kissing, and sexual activity. You may need to sleep in a separate bed from your partner.
  • Keep the toilet very clean. Men should urinate sitting down to avoid splashing. Flush the toilet 2 or 3 times after each use. Wash your hands well with soap and lots of water each time you use the toilet.
  • Rinse the bathroom sink and tub well after you use them.
  • Use separate towels, washcloths, and sheets. Wash these and your personal clothing by themselves. Don't wash them with other people's laundry.
  • You may want to use a special plastic trash bag for all your trash, such as bandages, paper or plastic dishes, menstrual pads, tissues, or paper towels. Talk to your treatment facility to see if they will handle the disposal. Or after 80 days, this bag can be thrown out with your other trash.
  • Wash your dishes in a dishwasher or by hand. If you use disposable dishes, they must be thrown away in the special plastic trash bag.
  • Don't cook for other people. If you must cook, use plastic gloves. Then throw them away in the special plastic trash bag. Don't share cups, dishes, or utensils.

Pregnancy and children

  • Your doctor will tell you when it is safe to have sex and become pregnant.
  • You should not breastfeed your baby after you have been treated with radioactive iodine. Ask your doctor when it's safe to breastfeed.


  • Don't take public transportation. If you are able, it's best to drive yourself.
  • It is important to prepare for any problems you may have at airport security. People who have had radioactive iodine treatment can set off the radiation detection machines in airports for a week to 10 days. Check with local authorities about any steps or permission you may need to travel.
  • If you plan to travel on the interstate, you may set off radiation detectors. Most police and transportation workers are aware of medical radiation, but it may help to carry some paperwork from your doctor.

How well does radioactive iodine treatment for hyperthyroidism work?

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.

What are the risks of radioactive iodine treatment?

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.

What can you expect after radioactive iodine treatment?

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:

  • 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.

After radioactive iodine therapy: When to call

Watch closely for any changes in your health, and be sure to contact your doctor if:

  • You have a sore throat.
  • You vomit.
  • You have diarrhea.

After radioactive iodine treatment: Overview

Radioactive iodine is absorbed and concentrated by the thyroid gland. You get it in liquid or pill form. The radiation will pass out of your body through your urine within days. Until that time, you will give off radiation in your sweat, your saliva, your urine, and anything else that comes out of your body. It is important to avoid exposing other people to the radioactivity from your body.

Your doctor will give you more written instructions. Follow these carefully. The instructions will tell you how far to stay away from people and how long you need to follow precautions. They will list other ways to keep other people safe. They will also tell you when it will be safe to go out, go to work, and do other activities.

Why is radioactive iodine treatment done?

Radioactive iodine may be used to treat hyperthyroidism in people who have noncancerous (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.

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.