Radio-iodine treatment procedure in case of hyperthyroidism

The function of the thyroid gland is to produce hormones that regulate the body's development, growth and metabolism. When the thyroid is overactive, it produces too much of the thyroid hormones.

In autoimmune hyperthyroidism (diffuse toxic goiter or Graves' disease), the entire thyroid gland is overactive. In autonomous thyroid adenoma and toxic multinodular goiter, thyroid nodules produce excess thyroid hormones.

Indications for radioiodine therapy:

  • autoimmune hyperthyroidism (diffuse toxic goiter or Graves' disease)
  • autonomous thyroid adenoma (toxic adenoma)
  • toxic multinodular goiter


If you have been taking tablets to control your hyperthyroidism, you will need to stop taking them at least two days before radioiodine therapy. Sometimes it is necessary to continue taking tablets for some time after radioiodine therapy, in which case treatment is resumed on the third day after administration of radioiodine. Your doctor will give you detailed instructions.

You should not eat for 4 hours before taking the radioiodine capsule. You may drink water. The radioiodine capsule looks like those used for many other medications and you swallow it with water.

After the administration of the radioactive capsule, you must follow the instructions in the document ‘Radiation safety requirements for patients receiving radioisotope therapy’.

The decision on the need for radioiodine therapy is made by a nuclear radiologist and your treating physician. The dose of radioiodine required for treatment is determined based on previous tests. The therapeutic effect is only achieved after a couple of months. To assess the outcome, levels of thyroid hormones in the blood are measured.

The procedure is performed in an outpatient setting. The patient is not hospitalised.

For more information about the procedure, see patient information.


Eve Kelk
Eve Kelk
Chief Physician
Diagnostic Clinic, Centre of Nuclear Medicine