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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.
While radiation can cause thyroid cancer, treatment of hyperthyroidism with radioactive iodine does not increase your chances of getting thyroid cancer.
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:footnote 1
After treatment, you may have follow-up examinations every 4 to 6 weeks to check your thyroid hormone levels.
Radioactive iodine may be used to treat hyperthyroidism in people who have non-cancerous (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.
Some side effects from radioactive iodine treatment include:
If you have Graves' ophthalmopathy, also called thyroid eye disease, it may get worse temporarily after radioactive iodine therapy.
CitationsSisson 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: March 1, 2023
Author: Healthwise Staff
Medical Review:E. Gregory Thompson MD - Internal Medicine & Kathleen Romito MD - Family Medicine & Matthew I. Kim MD - Endocrinology
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