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Women's Health

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Thyroid Scan

How To Prepare continued...

Before a thyroid scan, blood tests are usually done to measure the amount of thyroid hormones (TSH, T3, and T4) in your blood.

To prepare for a thyroid scan:

  • Do not eat for 2 hours before the test.
  • Tell your doctor about all of the medicines, vitamins, and supplements you are taking. You may need to stop taking some medicines or supplements for a while before the test.

Your doctor may ask you to eat a low-iodine diet for several days if this test is being done to check for thyroid cancer.

For a thyroid scan, you will either swallow a dose of radioactive iodine or be given technetium in a vein (intravenously) in your arm. When and how you take the radioactive tracer depends on which tracer is used.

  • Iodine can be taken as a capsule or a fluid 4 to 24 hours before the scan is done. Iodine has little or no taste.
  • Technetium is given 5 to 30 minutes before the scan is done.

Just before the test, you will remove your dentures (if you wear them) and all jewelry or metal objects from around your neck and upper body.

You will be asked to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

A thyroid scan is done in the nuclear medicine section of a hospital's radiology department by a person trained in nuclear medicine (nuclear medicine technologist).

The tracer used in this test is either radioactive iodine or technetium. You will either swallow a dose of iodine 4 to 24 hours before the scan or be given technetium in a vein (intravenously) in your arm 5 to 30 minutes before the scan.

WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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