Radioactive Iodine Therapy

What is radioactive iodine (RAI) therapy?

Radioactive iodine (RAI) therapy can treat hyperthyroidism (overactive thyroid) and certain types of thyroid cancer.

The term “radioactive” may sound frightening, but it’s a safe, generally well-tolerated treatment. It targets thyroid cells specifically to permanently destroy them. There’s little exposure to the rest of your body’s cells. Still, there are certain precautions you’ll have to take because you can emit (give off) small amounts of radiation that could affect other people.

Your thyroid gland needs iodine to make thyroid hormones. You typically get the iodine you need naturally through the foods you eat and iodized salt. In RAI therapy, your thyroid takes up radioactive iodine, which kills thyroid cells using radiation. It’s a type of nuclear medicine treatment.

Healthcare providers use iodine-131 for radioiodine therapy. It’s available as oral capsules, an oral drinking solution and IV injections.

Radioactive iodine therapy for hyperthyroidism

Hyperthyroidism can happen due to Graves’ disease, in which your entire thyroid gland is overactive. Or thyroid nodules can become overactive — called “toxic” nodules.

There are other treatments for hyperthyroidism, like antithyroid medications and thyroid removal surgery (thyroidectomy). Healthcare providers typically only recommend radioactive iodine therapy for hyperthyroidism if:

• Antithyroid medications haven’t worked or you’re unable to take them.
• Surgery is too risky based on your health or other factors.
• You have a decreased life expectancy.

RAI usually leads to permanent destruction of your thyroid, which will cure hyperthyroidism. Most people who receive this treatment must take thyroid hormone medication (levothyroxine) for the rest of their lives to maintain normal thyroid hormone levels.

Radioactive iodine therapy for thyroid cancer

If you have papillary thyroid cancer (PTC) or follicular thyroid cancer, radioactive iodine therapy may be part of your treatment plan.

Your healthcare team may recommend RAI therapy to destroy any thyroid tissue that they couldn’t remove with surgery. It can also treat thyroid cancer that’s spread (metastasized) to your lymph nodes and other parts of your body.

RAI therapy doesn’t work for anaplastic thyroid cancer and medullary thyroid cancer because these types of cancer don’t take up iodine.

Who isn’t a good candidate for radioactive iodine therapy?

Healthcare providers won’t let you receive radioactive iodine therapy if you:

• Are pregnant. Radioiodine can pass through the placenta and negatively affect fetal development.
• Are breastfeeding (chestfeeding).
• Have moderate to severe Graves’ ophthalmopathy.
• Have severe thyrotoxicosis (very high thyroid hormone levels).
• Are vomiting and/or have diarrhea.

How do I prepare for radioactive iodine therapy?

You’ll likely meet with your healthcare team at least a month in advance to go over the details of RAI therapy and how to prepare. Preparation steps may include:

• Blood tests to check your thyroid hormone levels.
• Stopping any thyroid-suppressing medicines (propylthiouracil or methimazole) at least one week before the procedure.
• Following a low-iodine eating plan for one to two weeks before the procedure. Your healthcare provider will let you know which foods to avoid.
• Receiving injections of thyroid-stimulating hormone (TSH) to increase how much radioactive iodine your thyroid will absorb.
• If you’re currently breastfeeding and are willing to stop, you’ll need to stop at least six weeks before the procedure.

Just before the procedure, you may:

• Need to take a pregnancy test. RAI therapy isn’t safe for pregnancy.
• Have a body scan if you have thyroid cancer to check for any remaining cancer cells in your body.
• Take medication to prevent nausea and vomiting during the procedure.

Your healthcare team will go over all these preparation steps in detail. Be sure to follow their instructions, and don’t hesitate to ask questions.

What happens during radioactive iodine therapy?

The procedure for RAI therapy is typically brief — it’s just a matter of swallowing the radioiodine or getting an IV injection in a hospital. The preparation for the procedure and the precautions you need to take after are more time-intensive than the treatment itself.

RAI therapy procedure for hyperthyroidism

For hyperthyroidism, you take radioactive iodine by mouth in a single capsule or liquid dose. This is usually an outpatient procedure, which means you take the dose in a hospital and can then go home afterward. After you swallow the radioiodine, your bloodstream quickly absorbs it in your gastrointestinal (GI) tract, and it collects in your thyroid gland. The radioactive iodine causes your thyroid to shrink and thyroid hormone levels to go down.

RAI therapy procedure for thyroid cancer

If you’re getting RAI therapy for thyroid cancer, you’ll take a dose of radioactive iodine by mouth or through an IV injection. This dose is larger than it is for treating hyperthyroidism. You may need to stay in a hospital after this procedure.

Most people just need one dose. But some need a second treatment. The radioiodine will destroy any remaining thyroid cancer tissue.

What happens after RAI therapy?

After you receive radioactive iodine, a healthcare provider will monitor you for any issues or complications. Depending on the size of the dose and other factors, you may be able to go home afterward, or you may need to stay in the hospital.

Your healthcare team will go over all the precautions to take if you go home.

What happens to your body after radioactive iodine therapy?

Radioactive iodine stays in your body for only a brief time. Your body gets rid of most of it during the first few days after treatment. Radioactive iodine leaves your body mainly through your pee. But there may be small amounts in your spit, sweat and poop.

What precautions should I take after RAI therapy?

RAI therapy doesn’t generally harm the rest of your body — just your thyroid. But you can emit (give off) radiation through bodily fluids (like pee, spit and sweat), which can affect other people. Because of this, you’ll need to take certain precautions to protect the people around you.

Your healthcare team will go over in detail what you should do. Steps to take may include:

• For the first 8 hours after treatment, maintaining a distance of at least 3 feet from people. Stay 6 feet away from pregnant people and children.
• Sleeping alone and avoiding prolonged intimate contact (including sexual intercourse and kissing) for three or four days. You can still have brief periods of close contact, like handshaking or hugging.
• Drinking enough fluids to “flush out” the radiation.
• Sitting when you go pee and flushing twice after you use the bathroom. If possible, designate one bathroom in your home as your own that nobody else can use after RAI therapy. Avoid using public restrooms.
• Washing your hands frequently.
• Bathing or showering daily.
• Washing your clothes, sheets (linens) and towels daily. Don’t share these items. Wash them separately from other people’s laundry.
• Avoiding preparing food for others that requires prolonged handling with your bare hands.
• Using your own dishware, cups and eating utensils and washing them separately from others’. Don’t share these items.
• Avoiding public transportation, if possible.
• Avoiding long automobile trips with others.

Your healthcare provider will let you know how long to follow these precautions.

Most healthcare providers recommend that people assigned female at birth (AFAB) avoid pregnancy for six to twelve months following treatment. People assigned male at birth (AMAB) should avoid conception for at least six months following treatment.

How long do you have to stay isolated after radioactive iodine?

You typically need to isolate or distance yourself from others after radioactive iodine therapy for at least three days. But it could be as long as two weeks. The length of time varies based on your dose of radioiodine and other factors. People who get RAI for thyroid cancer generally need to isolate for longer than those who get the treatment for hyperthyroidism.

Your healthcare team will give you specific instructions for your situation. Don’t hesitate to ask questions.

What are the advantages of radioactive iodine therapy?

Radioactive iodine is effective at destroying thyroid tissue, specifically. So, it’s a reliable form of treatment for certain thyroid conditions.

How successful is radioactive iodine therapy?

Radioactive iodine therapy generally has high rates of success. One study of 138 people who had RAI therapy for hyperthyroidism found that the success rate (cure rate) was 87.7% for those who had one dose of radioiodine.

What are the side effects of radioactive iodine therapy?

Short-term side effects of RAI therapy may include:

• Neck tenderness and swelling.
• Salivary (spit) gland swelling. This may look like cheek swelling.
• Dry mouth.
• Inflammation in your stomach lining (gastritis).
• Taste changes.
• Dry eyes.

Chewing gum or sucking on hard candy after the procedure may help with salivary gland issues and dry mouth.

One long-term side effect of RAI therapy is very low or absent thyroid hormone levels that require lifelong hormone replacement medication. This is a common and expected side effect.

Is radioactive iodine therapy painful?

You may experience mild pain in your thyroid after radioactive iodine therapy. It may feel like a sore throat. Ask your healthcare provider about over-the-counter (OTC) pain relievers you could take if this happens to you.

What are the risks of radioactive iodine therapy?

Risks of radioactive iodine therapy include:

• Low sperm count and male infertility for up to two years after treatment.
• Irregular periods (menstruation) for up to one year after treatment.
• Thyroid storm (extremely high thyroid levels).

All of these risks or complications are rare.

You may also have a slightly increased risk of developing:

• Leukemia.
• Salivary gland cancer.
• Stomach cancer.
• Thyroid cancer (if you had RAI for hyperthyroidism).

You can expose others around you to radiation in the days after the procedure. Because of this, your healthcare team will give you specific instructions for decreasing the risk of exposure to others. Exposure is especially risky for pregnant people, babies and young children.

How long does it take for radioactive iodine therapy to work?

For hyperthyroidism, it can take between one and three months before you start seeing the effects of RAI therapy. The full effect occurs three to six months after treatment. Usually, a single dose is all you need to treat hyperthyroidism. Rarely, you may need a second treatment.

When can I go back to work after RAI therapy?

Your healthcare provider will likely recommend not going back to work for at least three days after the procedure if you work near others. But this could be shorter or longer based on the dose you received and what you do for work.

When should I call my healthcare provider?

If you have any follow-up questions about the procedure or have any bothersome side effects, call your healthcare provider.

If you have trouble breathing, go to the nearest emergency room as soon as possible.

A note from Cleveland Clinic

The thought of swallowing a radioactive substance can be alarming. But know that radioactive iodine therapy is generally safe and effective. While it’s safe for you, the radiation you emit in the days following may be harmful to others. Because of that, you’ll need to take several precautions. Make sure you understand all of them and have a plan for after the procedure. Your healthcare team is available to answer any questions.