Radioactive iodine uptake

What is a Radioactive Iodine Uptake Test?

A radioactive iodine uptake (RAIU) test is a nuclear medical procedure used to measure the rate at which radioactive iodine (an isotope) is taken up by the thyroid gland. This test helps to diagnose and monitor various thyroid conditions, such as Grave’s disease.

Preparation for a Radioactive Iodine Uptake Test

Your doctor may ask you to stop taking certain medications for at least a few days before your test, as these medications can interfere with the results. If you are pregnant or breastfeeding, be sure to tell your doctor.

You may also be asked to fast for a few hours before the test. Your doctor may also require you to drink several glasses of water, to help flush the radioactivity through your body.

Procedures for a Radioactive Iodine Uptake Test

The test is conducted in two parts. In the first part, you will be given a small oral dose of the radioactive isotope iodine. You will then wait for 1 or 2 hours, during which time the thyroid will absorb the iodine. In the second part of the test, a special camera or a scanning device will be used to measure the amount of iodine that has been taken up from the thyroid.

Types of Radioactive Iodine Uptake Test

There are several types of RAIU tests, which may vary depending on the equipment used and your medical history. Some of the most common types of RAIU tests are:

  • Thyroid Scan—During this type of scan, the radioactive iodine is injected directly into the bloodstream and the amount absorbed by the thyroid is then measured.
  • Urine Test—This test measures the amount of radioactive iodine in the urine over a 24-hour period.
  • Saliva Test—This test measures the amount of radioactive iodine in the saliva.

Risks associated with Radioactive Iodine Uptake Test

It’s important to note that radioactive iodine uptake tests are associated with some risks. The most common risk is radiation exposure, which can cause various symptoms such as headaches, fatigue, and nausea. If the radiation exposure is too high, it can lead to organ damage or even cancer.

Other, less common risks include allergic reactions and infection. If you have kidney or liver disease, your doctor may advise against taking this test.

Why is a Radioactive Iodine Uptake Test Performed?

Radioactive iodine uptake tests are commonly used to diagnose and monitor a wide range of thyroid conditions and diseases, including Grave's disease, thyroid cancer, and hyperthyroidism. The procedure is also used to plan or evaluate treatments, such as thyroid surgery.

When is a Radioactive Iodine Uptake Test Performed?

Your doctor may recommend a RAIU test if you show signs or symptoms of a thyroid disorder or if your blood tests indicate an abnormality of thyroid function. This test may also be recommended after the treatment of a thyroid disorder to assess its effectiveness.