A thyroid uptake and scan uses a radioactive substance and a scanning tool to test the thyroid gland. The scanner picks up where and how much the radioactive substance was taken up by the thyroid. This helps determine the structure, location, size, and activity of the gland.
Reasons for Test
The scan may be done to:
- Find cause of an overactive thyroid— hyperthyroidism
- Test how well the thyroid is working
- Find out if a thyroid nodule is making thyroid hormone the way it should
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The radioactive substance does not cause short-term health problems. The dose is very small and leaves the body quickly. But radiation doses may build up in the body over time. This can raise the risk of some cancers. The risk is higher in children and women who could get or are pregnant. The care team will weigh a person's risks and benefits before the test is done.
What to Expect
Prior to Test
The care team may meet with you to talk about:
- Any allergies you may have
- Current medicines, herbs, and supplements that you take and whether you need to stop taking them before the test
- Fasting before the test, such as avoiding food or drink after midnight the night before
- Whether you are pregnant or breastfeeding
- Whether you have had any recent imaging tests
- Whether you need a ride to and from the test
- Tests that will need to be done before the test, such as checking the amount of thyroid hormone in the blood
Description of the Test
A radioactive substance will be given by mouth. Once it has had time to collect in the thyroid, the scan begins. You will lie on your back with your head tilted back. You will be asked to lie very still at certain times. A scanner will take pictures of the thyroid from different angles. The camera is not an x-ray machine. It does not expose you to more radiation. You may need to return to the radiology department after 24 hours for more pictures.
How Long Will It Take?
The radioactive substance needs time to be absorbed before the scan. You may need to wait 4 to 6 hours if you take the substance by mouth. The scan itself takes about half an hour.
Will It Hurt?
This test does not cause pain.
At the Care Center
You will be able to leave after the test is done.
The radioactive substance will leave the body in 1 to 2 days. It will not expose other people to radiation.
The pictures of the scan take about an hour to develop. A radiologist will look at them. Based on the results, more tests or treatment may be needed.
Call Your Doctor
Call the doctor if you have any unusual pain or discomfort.
If you think you have an emergency, call for medical help right away.
American Thyroid Association http://www.thyroid.org
Hormone Health Network—Endocrine Society http://www.hormone.org
Public Health Agency of Canada http://www.phac-aspc.gc.ca
The Thyroid Foundation of Canada http://www.thyroid.ca
Hyperthyroidism. Johns Hopkins University website. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/hyperthyroidism. Accessed August 19, 2021.
Hyperthyroidism and causes of thyrotoxicosis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/hyperthyroidism-and-other-causes-of-thyrotoxicosis-37. Accessed August 19, 2021.
Thyroid nodule. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/thyroid-nodule. Accessed August 19, 2021.
Thyroid nodules. American Thyroid Association website. Available at: http://www.thyroid.org/thyroid-nodules. Accessed August 19, 2021.
Thyroid scan and uptake. Radiological Society of North America Radiology Info website. Available at: https://www.radiologyinfo.org/en/info/thyroiduptake. Accessed August 19, 2021.
- Reviewer: EBSCO Medical Review Board James Cornell, MD
- Review Date: 07/2021
- Update Date: 08/19/2021