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A thyroid scan uses a radioactive tracer and a special camera. The tracer can be swallowed or can be injected into a vein. It travels through your body, giving off radiation signals. The camera "sees" the signals and can measure how much tracer the thyroid absorbs from the blood.
A thyroid scan is done to:
You may need to stop eating for several hours before the test. If the test is being done to check for thyroid cancer, you may have to eat a low-iodine diet for several days before the test. Your doctor may have you stop taking thyroid medicines for some time before this test.
If you are breastfeeding, you may want to pump enough breast milk before the test to get through 1 to 2 days of feeding. The radioactive tracer used in this test can get into your breast milk and is not good for the baby.
After you get the tracer, you may have a scan about 30 minutes later. Or you may need to return up to 24 hours later for one or more scans. Each scan takes only a few minutes.
Anytime you're exposed to radiation, there's a small chance of damage to cells or tissue. That's the case even with the low-level radioactive tracer used for this test. But the chance of damage is very low compared with the benefits of the test.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.
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Current as of: December 19, 2022
Author: Healthwise Staff
Medical Review:Kathleen Romito MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine
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