How to Prepare for Thyroid Function Testing

Prepare Thyroid

What Is Thyroid Function Testing?

Thyroid function testing is a screening process that determines if your thyroid, a butterfly-shaped gland in the throat, is functioning properly. The thyroid produces hormones that regulate several body functions, including metabolism. By determining if your thyroid is functioning normally, your doctor can diagnose any potential problems and prescribe the right treatment.

Reasons to Get Thyroid Function Testing

Your doctor may order thyroid function testing if they suspect you are experiencing thyroid issues. These tests can help determine if you have an overactive or underactive thyroid, or if you have a related disorder such as Graves’ disease, Hashimoto’s thyroiditis, or thyroid nodules. Testing is also done prior to starting thyroid medications.

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Preparing for Thyroid Function Testing

Your doctor may suggest certain tests to prepare for your thyroid function testing. If you are to undergo blood tests, you should fast for 8 to 12 hours before the test. You may also be asked to avoid foods or medications that can interfere with the accuracy of the test results, such as iron supplements. Tell your doctor about any family history of thyroid issues or skin conditions, as these can also affect the results. It is important to discuss any medications you are taking prior to thyroid function testing, as some drugs may interfere with test results.

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What to Expect During the Test

Thyroid function testing can be done in various ways. Your doctor may order a physical exam to look for any enlargement or lumps in the thyroid. Blood tests can measure the levels of hormones produced by your thyroid as well as any antibodies that may be present.
Your doctor may also order an imaging test, such as an ultrasound or CT scan, to look for any abnormalities in the thyroid.

Key Points To Remember

  • Thyroid function testing is a screening process that helps diagnose potential thyroid problems or disorders.
  • Your doctor may ask you to fast for 12 hours and to avoid certain foods and medications prior to the test.
  • It is also important to discuss any medications you are taking prior to the test.
  • Thyroid function testing can include physical exams, blood tests, and imaging tests.


Thyroid function testing is an important preventative measure that helps diagnose any potential thyroid issues. Preparing for the test is essential to ensure accurate results. By fasting and avoiding certain foods or medications, as well as discussing any medications you may be taking, you can help ensure that your thyroid function testing will be accurate.