Radioactive iodine is considered by many doctors to be the best treatment for hyperthyroidism. You swallow it in a liquid form or capsule, and the iodine is taken up by your thyroid gland. The radioactivity in the iodine kills most or all of the tissue in your thyroid gland. But it does not harm any other parts of your body.

What to think about

Most people are cured of hyperthyroidism after one dose of radioactive iodine.

The main drawback of radioactive iodine is that it can damage your thyroid gland so that your body no longer produces enough thyroid hormone. This is a common result of treatment. And most people who receive radioactive iodine eventually develop hypothyroidism (having too little thyroid hormone). If you develop hypothyroidism, you will need to take thyroid hormone medicine for the rest of your life. For more information, see the topic Hypothyroidism.

Radioactive iodine should not be used by children or by women who are pregnant, women who are breast-feeding, or women who want to become pregnant within 6 months of treatment.

Doctors have used radioactive iodine to treat hyperthyroidism for more than 60 years. There is no evidence that radioactive iodine causes cancer, infertility, or birth defects.

Hyperthyroidism: Should I Use Antithyroid Medicine or Radioactive Iodine?