What is a thyroid scan?

A thyroid scan is a test of your thyroid gland using a chemical called a radioactive tracer. The chemical is detected by a device called a scanner. Your thyroid gland is in the lower front of your neck. Hormones made by the thyroid gland control the way your body turns the food you eat into energy. They also control body functions such as temperature, heart rate, and appetite.

When is it used?

This test is done to diagnose problems with your thyroid gland. The scan shows the size and shape of your gland and if there are any abnormal areas.

Ask your healthcare provider to explain why you are having the test and any risks.

How do I prepare for this scan?

• You may or may not need to take your regular medicines the day of the test. Tell your healthcare provider about all medicines and supplements that you take. Ask your provider if you need to avoid taking any medicine or supplements before the test.
• Tell your healthcare provider if you have any food or medicine allergies.
• Tell your provider if you have had kidney problems or an allergy to chemicals, such as contrast dye. Contrast dye is used for some scans.
• Before you have a thyroid scan, you may have a blood test to check the level of thyroid hormone.
• Your healthcare provider will give you capsules containing a radioactive chemical, such as iodine. You will swallow these capsules 4 to 24 hours before the test. In some cases, your provider may give you the radioactive chemical through an IV about 30 minutes before the test.
• Follow any other instructions your healthcare provider gives you.
• Ask any questions you have before the test. You should understand what your healthcare provider is going to do. You have the right to make decisions about your healthcare and to give permission for any tests or procedures.

What happens during the scan?

The radioactive tracer will be taken up by your thyroid gland as the gland makes thyroid hormone.

To start the scan, you will lie on an exam table while a scanner is held near your neck. The scan will measure where the tracer goes, and how much of it is in different areas of your thyroid gland. You may have another scan 24 hours later.

What happens after the scan?

You can go home after the scan is completed.

Ask your healthcare provider:

• How and when you will hear your test results
• What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for another scan or checkup.

What are the risks of this scan?

Every procedure or treatment has risks. You could have an allergic reaction to the dye. Ask your healthcare provider how this risk applies to you.

The amount of radioactive material given for this scan is very small and is not a risk.

Be sure to discuss any other questions or concerns that you may have.