About Radioactive Iodine Uptake Test | Endocrinology

Radioactive iodine uptake test

What is radioactive iodine uptake test?

A radioactive iodine uptake test (RAIU) uses a radioactive tracer and an exceptional probe to measure how considerable tracer the thyroid gland absorbs from the blood. The radioactive iodine uptake test can show how much of the marker is absorbed by the thyroid gland. The RAIU test is often done in conjunction with a thyroid scan, which shows if the marker is evenly distributed in the gland. This helps your physician know if the thyroid gland is working accurately. The radioactive tracer that is commonly used in this test is iodine.

A radioactive iodine uptake test is done to find problems with the functioning of the thyroid gland, such as hyperthyroidism.

Types of radioactive iodine uptake test

Radioactive iodine uptake testis a type of nuclear test that measures the amount of radioactive iodine absorbed by the thyroid gland in a set period of time. You are asked to swallow (swallow) radioactive iodine (I-123 or I-131) in liquid or capsule form.

  • Hypothyroidism
  • Subacute thyroiditis
  • Iodine overload (excessive intake of iodine)

Radioactive iodine uptake test

Depending on the dose, radioactive iodine can kill part or all of the thyroid. Your physician will order a radioactive iodine acceptance and scan to determine your dose, the cause of your hyperthyroidism, and information about your thyroid tissue.

In this test, you swallow a very small dose of radioactive iodine. Your doctor will monitor your thyroid’s activity level by measuring the amount of iodine it absorbs. He or she will do this by scanning your thyroid, which will show healthy and diseased tissues.

In determining the best dose, the size of the thyroid gland (determined by a physical exam) and the results of the uptake test are the two most important factors. The larger the gland, the higher the dose of radioactive iodine. The higher the absorption of iodine, the lower the dose.

How radioactive iodine uptake test works?

Radioactive iodine uptake test is available as an oral pill, so you will not have to be hospitalized. After taking the pill, your doctor will advise you to drink plenty of fluids to cause the release of radioactive iodine through your urine.

Fortunately, radioactive iodine therapy is aimed at treating only the thyroid gland. Thyroid cells are the main cells in the body that can absorb iodine, so there is very little radiation exposure to the rest of the body’s cells. When thyroid cells absorb radiation, they are damaged or destroyed.

About 90% of patients need only one dose before their hyperthyroidism is cured. Although you may only need a single dose, it may take up to six months for the medicine to completely destroy part or all of your thyroid. Fortunately, most patients experience a reduction in symptoms about a month after treatment.

If your symptoms persist 6 months after treatment, you may essential a second dose. In the fewest cases, some patients will not benefit from a second dose and may in its place require surgery.

Side effects of radioactive iodine uptake test

The most common side effect of radioactive iodine may seem ironic, but it makes perfect sense: hypothyroidism. Radioactive iodine often kills too many thyroid cells, leaving the thyroid unable to produce enough hormones – the opposite problem it had before.

It may seem strange to replace one disorder with another, but hypothyroidism is much easier to treat in the long term than hyperthyroidism. If you develop hypothyroidism, you will need to take thyroid hormone replacement therapy for life, but it is a safe, reliable, and cost-effective treatment.

Other side effects of radioactive iodine uptake include:

  • Metallic flavor in the mouth: This can last for a few weeks
  • Nausea: Usually disappears a day or two after treatment
  • Swollen salivary glands: This can last a few weeks. It is caused by iodine absorbed by the salivary glands, although stimulating the flow of saliva one day after treatment (sucking on a drop of lemon, for example) is an effective remedy.

Risks factors for radioactive iodine uptake test

The radiation dose in this test is small and is not associated with any dangerous side effects. However, as an added precautionary measure, the test is not recommended for pregnant or lactating women. There are potential risks when exposing a fetus or baby to radioactive material. Tell your doctor if there is a possibility that you are pregnant or if you are breastfeeding. Your doctor may use other means, such as blood tests and physical exams, to monitor your condition.

Tell your doctor if you are allergic to iodine or shellfish (allergies to shellfish may be due to the iodine they contain). This could interfere with your ability to perform this test.

Procedure of radioactive iodine uptake test

You will be given a pill or liquid that contains radioactive iodine. It will take time for the iodine to get into your system so that your thyroid can absorb it.

You will be allowed to eat again within an hour or two after ingesting the radioactive iodine. However, until the test is complete, you will have to follow the same dietary limitations that you monitored in preparation for the test.

You will be asked to return to the testing center at certain intervals (usually six and 24 hours after ingesting the radioactive iodine). At this time, you will be asked to sit down and the technologist will place a device called a gamma probe over your thyroid gland (on the outside of your neck). There is no pain. Each scan takes only about five minutes, although you may be asked to sit for additional images if the first ones are not clear.

The gamma probe measures the amount of radioactive iodine that the thyroid has absorbed at the time of the scan.

You will excrete the radioactive iodine in your urine for 24 to 48 hours after the test. The amount of radioactive iodine uptake test used in an RAIU scan is so small that you don’t need to take any precautions.

Precautions for radioactive iodine uptake test

Because your body retains and then emits radiation after treatment with radioactive iodine, you will need to follow certain precautions to ensure your safety and the safety of others.

These precautions also apply if a family member or friend brings you to your treatment. You will be advised to keep a distance of three feet from others for several days after radioactive iodine therapy. You will also need to wait several days before taking an extended car trip with other people.

Over time, the amount of radiation in your body will decrease and eventually disappear. Depending on the dose of treatment you initially received, you may need to break in the hospital for several days to allow the level of radiation in your body to reduce before you go home. Once you are home, you may need to cut back on certain activities, such as having contact with children and pregnant women, and return to work immediately, so that radiation levels can drop to safer levels.


The greater the distance you have from others; the less radiation they will receive. You will be advised to sleep only for the first few days after your treatment. During this period, you should avoid kissing or sexual intercourse. Also avoid prolonged physical contact with other people, especially children, and pregnant women.


Exposure to radiation from other people depends on how long you stay in close contact with them. You will be advised to minimize the time you spend in close contact with other people. Drink plenty of fluids, such as water or juices, to help you urinate frequently. This should help eliminate radioactive iodine, thereby reducing the amount in your body.


Good hygiene reduces the chance of contaminating others. The guidelines are to wash your hands with soap and plenty of water every time you go to the bathroom. Keep the toilet very clean. Also, flush the toilet two or three eras after each use. Rinse the sink and bathtub well after use to reduce the chance of exposing others to the radioisotope in your saliva and sweat. Use separate eating utensils for the first few days and wash them separately to reduce the chance of contaminating other family members with radioactive iodine in your saliva.

Pregnant women and nursing mothers

If you are pregnant or think you are, tell your doctor that radioactive iodine uptake test should not be given during pregnancy. If you plan to become pregnant, ask your doctor how long to wait after treatment.

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