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Home > Patient & Family Resources > Health Library > Radioactive Iodine
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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.
See a picture of the thyroid gland.
While radiation can cause thyroid cancer, treatment of hyperthyroidism with radioactive iodine does not increase your chances of getting thyroid cancer.
Within days, the radioactive iodine passes out of your body in your urine and saliva. How long it takes will depend on the dose you received and your age. Young people get rid of radioactive iodine faster than older adults.
Most people don't feel different after treatment. But a few people may feel a little nauseated.
Your doctor will give you written instructions. To avoid exposing other people to radioactivity, it is important to follow your doctor's instructions 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 directed to avoid close contact, kissing, sex, and sharing cups, dishes, or utensils.
Some general recommendations include:footnote 1
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.
In almost all cases, your thyroid hormone levels will return to normal or below normal after radioactive iodine treatment. This may take 8 to 12 weeks or longer. If your thyroid hormone level does not go down after 6 months, you may need another dose of radioactive iodine.
If you have thyroid cancer and you are treated with radioactive iodine, it may take from several weeks to many months for your body to get rid of any remaining cancer cells.
Your thyroid nodule is unlikely to grow after being treated with radioactive iodine.
The risks from radioactive iodine treatment include:
If you are pregnant, you should not receive radioactive iodine treatment. This kind of treatment can damage your fetus's thyroid gland or expose your fetus to radioactivity.
You should not breastfeed your baby after you have been treated with radioactive iodine. Ask your doctor when it is safe to breastfeed.
Different people with thyroid cancer will receive different doses of radioactive iodine. If you are young and you do not have a great risk of your cancer coming back, you will probably need less radioactive iodine than an older person. Sometimes this means that a younger person who receives radioactive iodine treatment will not have to stay overnight in a hospital.
Traveling after treatment
If you have had radioactive iodine treatment and you want to travel 3 to 4 days after treatment, 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.
Sisson JC, et al. (2011). Radiation safety in the treatment of patients with thyroid diseases by radioiodine 131I: Practice recommendations of the American Thyroid Association. From the American Thyroid Association Taskforce on Radioiodine Safety. Thyroid, 21(4): 335–346.
Current as of: July 29, 2019
Author: Healthwise StaffMedical Review: E. Gregory Thompson, MD - Internal MedicineKathleen Romito, MD - Family MedicineMatthew I. Kim, MD - Endocrinology, Diabetes and Metabolism
Current as of: July 29, 2019
Author: Healthwise Staff
Medical Review:E. Gregory Thompson, MD - Internal Medicine & Kathleen Romito, MD - Family Medicine & Matthew I. Kim, MD - Endocrinology, Diabetes and Metabolism
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