Version July 2025
Please read the Disclaimer at the end of this page.
What is a thyroid uptake and scan? —
This is a test to check the thyroid gland. The thyroid is in the middle of the neck (figure 1). It makes thyroid hormone, which controls how the body uses and stores energy. The thyroid gland uses a mineral called "iodine" to make thyroid hormone. This test measures how much iodine the thyroid is absorbing.
For the test (figure 2):
●You swallow a pill that contains a chemical called a "radioactive tracer." Often, the tracer is a special form of iodine. Sometimes, you get a different tracer injected into a vein instead.
●A device measures how much of the tracer has been absorbed by your thyroid. This is the "uptake" part of the test.
●A special camera creates pictures of your thyroid. This is the "scan" part of the test. It can show the size and shape of your thyroid, and where it absorbed the tracer.
The test is generally done between 20 minutes and 24 hours after you get the tracer. The timing depends on why you are getting the test and the type of tracer.
Why might I get a thyroid uptake and scan? —
Your doctor might want you to get this test:
●To learn the cause of hyperthyroidism – This is when the thyroid makes too much thyroid hormone. Different things can cause this. If a blood test showed you have hyperthyroidism, your doctor might order a thyroid uptake and scan to learn more.
●If you have thyroid nodules – These are round or oval-shaped growths in the thyroid. They are common and usually not harmful. But sometimes, they can be related to a more serious condition such as cancer. A thyroid uptake and scan can help the doctor decide if nodules need more testing.
In some cases, doctors do a thyroid scan to check for thyroid cancer. When the test is used for this, a bigger dose of the tracer is used. The whole body is also scanned, not just the thyroid, and the scan might happen several days after getting the tracer.
How do I prepare for a thyroid uptake and scan? —
The doctor or nurse will tell you if you need to do anything special to prepare.
They will also ask about your "health history." This involves asking about any health problems you have or had in the past, past surgeries, and any medicines you take. Tell them about:
●Any medicines you are taking – This includes any prescription or "over-the-counter" medicines, plus any herbal supplements. It helps to write down and bring a list of your medicines, or bring a bag with all your medicines with you.
●Any allergies you have
●Any recent imaging tests (such as a CT scan or X-ray) that used "contrast"
●Whether you are pregnant, could be pregnant, or are breastfeeding – A thyroid uptake and scan is not done during pregnancy, because it is not safe for a developing baby.
If you are breastfeeding, you can get a thyroid uptake and scan if needed. But you will need to temporarily stop breastfeeding. During this time, you can pump and discard the milk. Your doctor will tell you how long you will need to avoid breastfeeding.
You will also get information about:
●Eating and drinking before the test – You need to "fast" before the test. This means not eating or drinking anything for a period of time.
●Whether to stop any of your medicines or change your diet before the test
Ask the doctor or nurse if you have questions or if there is anything you do not understand.
What happens during a thyroid uptake and scan?
●Your doctor or nurse will give you the tracer:
•If you are getting it by mouth, you will swallow a capsule. This might happen either 4 to 6 hours or 24 hours before the scan.
•If you are getting it through a vein, you will first get an "IV." This is a thin tube that goes into a vein. The person doing the scan (called a "technologist") will use your IV to inject the tracer. This happens about 20 minutes before the test.
●When it is time for the test, you might will be asked to remove any metal objects from your body, like jewelry, glasses, dentures, and hearing aids. You might be asked to change into a hospital gown.
●The technologist will use a device to measure how much of the tracer has been absorbed by your thyroid. They will hold the device close to your neck to do this. It only takes a few minutes.
●For the scan, you will most likely lie on a table with your head tilted back. The special camera will be moved around to take pictures of your thyroid. In some cases, it will take pictures of your whole body. The technologist might leave the room while the pictures are taken, but will be nearby.
●The scan usually takes about 30 minutes, but can take longer depending on how many pictures are needed.
What happens after a thyroid uptake and scan? —
The medical staff will remove your IV, if you had one. In most cases, you can go home right away.
The tracer used for this test is radioactive. For the next 1 to 2 days:
●Drink plenty of water to help your body get rid of the tracer.
●The tracer will come out of your body through your urine.
●Because the amount of radiation is very small, you do not need to avoid being around other people.
What are the risks of a thyroid uptake and scan? —
Your doctor will talk to you about all the possible risks, and answer your questions. Possible risks include:
●A minor or serious allergic reaction to the tracer
●Radiation exposure – A thyroid uptake and scan exposes you to some radiation. In general, exposure to radiation very slightly raises your risk of developing cancer later in life. But the amount of radiation used for this test is very small. The overall risk increases if you have to get many imaging tests over time.
What else should I know? —
You might get your test results the same day, or it might take a few days for them to be read by an expert. Your doctor or nurse will tell you when to expect your results.
If your thyroid uptake and scan shows any abnormal results, your doctor or nurse will talk to you about what to do next.
Patient education: Hyperthyroidism (overactive thyroid) (The Basics)
Patient education: Graves' disease (The Basics)
Patient education: Thyroid nodules (The Basics)
Patient education: Thyroid cancer (The Basics)
Patient education: Thyroid-stimulating hormone test (The Basics)
Patient education: Hyperthyroidism (overactive thyroid) (Beyond the Basics)
Patient education: Thyroid nodules (Beyond the Basics)
