Radioactive Iodine Uptake (RAIU) test: Reference Range

A radioactive iodine uptake (RAIU) is a test used to diagnose thyroid diseases. The test will show your thyroid function conditions.

In a RAIU test, you are asked to swallow radioactive iodine. After 6 to 24 hours, you are required to go back to have the radioactivity measured. A gamma probe is placed over your thyroid gland in the neck in order to measure the amount of radioactivity in the thyroid gland.

With a thyroid scan, the doctor can know the size, shape and position of the glans.

Normal Values

6 hours: 3 to 16%

24 hours: 8 to 25%

Reference Range

Increased (greater than 35% at 24 hours is considered elevated):

  • Hyperthyroidism
  • Hashimoto’s thyroiditis (early)
  • Goiter


  • Hypothyroidism
  • Subacute thyroiditis
  • Iodine overload (excessive iodine ingestion)

Keywords: radioactive iodine uptake test; RAUI test.

* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.