Radioactive Iodine Treatment

Medically Reviewed By William C. Lloyd III, MD, FACS
Was this helpful?

What is radioactive iodine treatment?

Radioactive iodine treatment uses radioactive iodine medication to treat thyroid cancer or an overactive thyroid (hyperthyroidism). The thyroid gland efficiently absorbs and concentrates iodine. Once in the thyroid, radioactive iodine destroys thyroid cancer cells, as well as the thyroid. Radioactive iodine treatment, also called radioiodine therapy or I-131 treatment, is available in a capsule or liquid form.

Radioactive iodine treatment is only one method of treating thyroid diseases, disorders and conditions. Discuss all your treatment options with your doctor to understand which options are right for you.

Other procedures that may be performed

Your doctor may recommend one or more additional procedures to treat thyroid cancer or hyperthyroidism including: 

  • Chemotherapy uses medications to slow or stop the growth of thyroid cancer cells.

  • External radiation therapy uses X-ray beams to kill thyroid cancer cells.

  • Surgery removes an overactive thyroid gland. You may also need surgery to remove all or part of a cancerous thyroid and possibly lymph nodes in the neck if the thyroid cancer has spread.

  • Thyroid hormone therapy uses drugs to prevent your body from making thyroid hormones or blocks their action to stop cancer cells from growing.

Why is radioactive iodine treatment performed? 

Your doctor, typically an endocrinologist, may recommend radioactive iodine treatment to treat thyroid cancer or an overactive thyroid gland, also called hyperthyroidism and Graves’ disease.

Who performs radioactive iodine treatment?

The following types of doctors determine the type and dose of oral radioactive iodine used in treatments:

  • Nuclear medicine doctors specialize in using radioactive materials to diagnose disease and guide treatment plans.

  • Nuclear radiologists specialize in using imaging technologies and radioactive materials to diagnose and treat disease.

  • Radiation oncologists specialize in treating cancer and related diseases with radiation.

  • Oncologists specialize in diagnosing, treating and preventing cancer.

  • Pediatric hematologist-oncologists specialize in researching, diagnosing and treating blood disorders and cancer in children.

How is radioactive iodine treatment performed?

Radioactive iodine treatment involves swallowing a prescribed dose of radioactive iodine in a capsule or liquid form. The thyroid efficiently absorbs and concentrates iodine from foods that contain iodine, such as iodized salt, as well as radioactive iodine. Once in the thyroid, radioactive iodine destroys thyroid tissue and thyroid cancer cells.

Will I feel pain?

Your comfort is important to both you and your care team. Radioactive iodine treatment is not painful. Some people have temporary side effects. They can include neck tenderness or pain, dry mouth, nausea, dry eyes, and swollen, sore salivary glands. Tell your doctor if you have side effects.

What are the risks and potential complications of radioactive iodine treatment?

Risks and potential complications of radioactive iodine treatment include:

  • Loss of taste and dry mouth

  • Low sperm counts or infertility in men

  • Temporary ovary dysfunction and irregular periods in women

  • Slight increased risk of developing leukemia (rare)

How do I prepare for my radioactive iodine treatment?

You are a very important member of your own healthcare team. The steps you take before your treatment can improve your safety and comfort, and help your doctor obtain the best results.

You can prepare for a radioactive iodine treatment by:

  • Abstaining from sex or using effective birth control to avoid pregnancy before and for up to a year after treatment

  • Answering all questions about your medical history, allergies, and medications. This includes any possible allergy to iodine or shellfish, and your prescriptions, over-the-counter drugs, herbal treatments, and vitamins. It is a good idea to carry a current list of your medical conditions, medications, and allergies at all times.

  • Following your doctor’s instructions for taking or stopping your medications

  • Telling your doctor if there is any possibility of pregnancy or if you are breastfeeding. Stop breastfeeding before radioactive iodine begins as directed by your doctor.

Questions to ask your doctor

Having radioactive iodine treatment can be stressful. It is common for patients to forget some of their questions during a doctor’s office visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before your procedure and between appointments.

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need radioactive iodine treatment? Are there any other options for treating my condition?

  • How should I take my regular medications?

  • Will I need to stay in the hospital after my radioactive iodine treatment? For how long?

  • What precautions do I need to take to protect others from radiation exposure?

  • What other treatments or tests might I need?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours.

What can I expect after my radioactive iodine treatment?

Knowing what to expect after a radioactive iodine treatment can help you get back to your everyday life as soon as possible. 

How will I feel after radioactive iodine treatment?

Most people feel fine after their radioactive iodine treatment. There are a few potential side effects, but they are uncommon and are generally temporary and treatable. Call your doctor if you have side effects including:

  • Change in taste

  • Dry eyes. If you have contacts, ask your doctor for instructions about wearing them.

  • Dry mouth and swollen or sore salivary glands. Your doctor may recommend sucking on hard candy or other strategies.

  • Nausea. Your doctor may recommend not eating immediately before to several hours after treatment.

  • Neck tenderness

  • Pain (rare)

Symptoms of hyperthyroidism improve gradually after radioactive iodine treatment. 
The symptoms and prognosis of thyroid cancer will vary depending on your specific case. Because radioactive iodine destroys the thyroid tissue, you will likely need to take thyroid hormone replacement for the rest of your life.

What precautions are necessary after radioactive iodine treatment?

Radioactive iodine treatment that is beneficial for you can be harmful to others. You will give off radiation after radioactive iodine treatment until it dissipates. You may need to stay in a special room in the hospital for a few days to avoid exposing others to radiation. This will depend on the dose of radioactive iodine and other factors. 

You will need to take special precautions at home for a short time to protect others from radiation exposure. Precautions vary depending on the dose of radioactive iodine. Your doctor will give you specific instructions for precautions such as:

  • Avoid close contact with others. Stay at least an arm’s length away from others for about 11 days after treatment. Avoid activities that put you in close contact with others, such as taking a trip by jet or in a car with your family.

  • Do not breastfeed.

  • Do not share food, utensils, dishes or bottles with others. Wash these items thoroughly and immediately after you use them. Do not cook for others if it involves touching the food with your bare hands.

  • Drink plenty of fluids to help flush out the radiation.

  • Sleep alone and do not have sex. Do not become pregnant for up to a year after treatment.

  • The radiation in your body may set off certain security systems, such as at the airport, for about three months. Your care team will give you a card that explains this. Carry the card with you for several months.

  • Urinate frequently. Flush the toilet immediately and twice after urination.

  • Wash your hands frequently.

  • Wash linens, clothing and towels daily and separately from laundry of others.

When should I call my doctor?

You should keep your follow-up appointments after radioactive iodine treatment. Call your doctor if you have any side effects, concerns, or questions between appointments. 

Was this helpful?
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 3
View All Thyroid Disorders Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. General Nuclear Medicine. American College of Radiology.
  2. Radioactive iodine (radioiodine) therapy for thyroid cancer. American Cancer Society.
  3. Radioactive Iodine Treatment. Diabetes & Hormone Center of the Pacific.
  4. Radioiodine (I -131) Therapy for Hyperthyroidism. American College of Radiology.
  5. Thyroid Cancer Treatment. National Cancer Institute.