A thyroid uptake and scan is a test that uses a radioactive substance and a scanning tool to evaluate 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.
The scan may be ordered to:
Determine the cause of an overactive thyroid (hyperthyroidism)
- Test how well the thyroid is working
- Determine if a thyroid nodule is functioning (if it is making thyroid hormone)
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Thyroid scans are associated with very few risks. Tell your doctor if you:
Have an allergy to medicine or food (including iodine or
- Are (or might be) pregnant or breastfeeding—the test could expose the baby to radiation
- Take any medicines on a regular basis—some can interfere with test results
If you recently had any
cardiac catheterizations, or other imaging tests that use contrast dye
- You may be asked to avoid certain food (containing iodine) or thyroid medicine before the scan. Some can interfere with the results.
- Jewelry, dentures, and other metallic objects will be removed.
- You may be asked not to eat or drink anything after midnight.
- Your doctor may order some tests to measure the amount of thyroid hormone in your blood.
The procedure is done by a trained technician in the radiology department of a hospital. You will be given a radioactive substance by mouth. Once the substance 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 your 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 additional pictures.
You will be able to leave after the test is done.
Because of the very low dose of radioactive substance used, the majority of the radioactive substance will leave your body within a day or two. You are not at risk for exposing other people to radiation. You can interact normally with them.
The scan itself takes about half an hour. The radioactive substance needs time to be absorbed before the scan. You may need to wait 4-6 hours if you take the substance by mouth.
There is no pain associated with a thyroid scan. There may be times when you find it uncomfortable to lie still with your head tilted backward.
The pictures of the scan take about an hour to develop. A radiologist will examine them. Based on the results of the test, further studies or treatment will be recommended.
Call your doctor if you experience any unusual pain or discomfort.
In case of an emergency, call for medical help right away.
Beers MH, Fletcher AJ, et al.
The Merck Manual of Medical Information: Second Home Edition. Whitehouse Station, NJ: Merck Research Laboratories; 2003.
Thyroid nuclear medicine scan. Dr. Joseph F Smith Medical Library website. Available at:
www.chclibrary.org/micromed/00068040.html. Accessed August 24, 2005.
Last reviewed December 2011 by Lawrence Frisch, MD, MPH
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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