Radioiodine (I-131) Therapy for Hyperthyroidism

ExitCare ImageRadioiodine (I-131) therapy for hyperthyroidism is a procedure used to treat an overactive thyroid (hyperthyroidism). The patient swallows I-131, which is a radioactive form of iodine. The I-131 destroys thyroid cells.

The thyroid is a gland in the neck. It makes thyroid hormones, which control how cells throughout the body use energy.

Hyperthyroidism is usually caused by Grave's disease or by growths within the thyroid (nodules). Symptoms may include:

  • Nervousness.

  • Irritability.

  • Problems with sleep.

  • Tiredness.

  • Fast heart rate.

  • Shaky hands.

  • Sweating.

  • Heat sensitivity.

  • Unintended weight loss.

  • Brittle hair.

  • Enlarged thyroid gland.

  • Menstrual changes.

  • Frequent stools.


  • All allergies.

  • All medications that you are taking, including over-the-counter and prescription drugs, dietary supplements, vitamins, or herbal preparations.

  • Any previous complications from this or other procedures.

  • Smoking history.

  • Possibility of pregnancy.

  • History of bleeding problems.

  • Any other health problems.


Risks of the procedure include:

  • Slight pain in the area of the thyroid gland.


  • If you are a woman, you may be asked to have pregnancy testing before the procedure.

  • If you have been taking thyroid medicines, you will usually be asked to stop them three days before your procedure.

  • You will usually be asked to stop eating and drinking at midnight the day of your procedure.

  • You will need to plan for someone to drive you home after the procedure.


You will be asked to swallow the radioactive iodine in either pill or liquid form. It can take 1-3 months for the treatment to work. The treatment is most effective at about 3-6 months after the dose of iodine has been given. In most people, a single dose of radioactive iodine resolves their hyperthyroidism, but a few people will require a second dose.


Because you will be giving off tiny amounts of radiation for several days, there are some special precautions you will be asked to follow for about 2-4 days after the procedure:

  • Avoid being around babies or pregnant women.

  • Do not use public bathrooms.

  • Flush twice after using the toilet.

  • Take a bath or shower every day.

  • Practice good hand washing.

  • Drink fluids normally.

  • Use disposable utensils, or clean your utensils separately from those of others.

  • Sleep alone.

  • Do not engage in intimate contact.

  • Wash your sheets, towels, and clothes each day, by themselves.

  • Do not make food for other people.

Other precautions include:

  • Stopping breastfeeding.

  • Do not attempt to become pregnant for at least a year after you have had the procedure.

  • When traveling, bring a letter of explanation from your caregiver for three months. Radioactivity may trip detectors in airports or other places.

Because the point of the procedure is to destroy your thyroid gland, you will need to take thyroid hormone by mouth for the rest of your life.


  • Ask your caregiver when you should resume or start thyroid medications.

  • Take all medications exactly as directed.

  • Follow any prescribed diet.

  • Follow instructions regarding both rest and physical activity.


  • You have a dry mouth.

  • You have a sore throat.

  • You have neck pain.

  • You have a tight sensation in the throat.

  • You have nausea and vomiting.

  • You are fatigued.

  • You have flushing.

  • You have bowel changes (either diarrhea or constipation).