Thyroid Hormone Tests: About This Test

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What is it?

Thyroid hormone tests are blood tests that check how well your thyroid gland is working. The thyroid gland is a butterfly-shaped gland that lies in front of your windpipe (trachea), just below your voice box (larynx). The thyroid gland makes hormones that control the way your body uses energy (metabolism).

This test will give your doctor information about your thyroid hormone levels. You may have hyperthyroidism when your thyroid makes too much thyroid hormone. You may have hypothyroidism when your body does not make enough thyroid hormone.

Why is this test done?

Thyroid hormone tests are done to:

  • Find the cause of an abnormal thyroid-stimulating hormone (TSH) test, which is a blood test that checks for thyroid gland problems.
  • Check how well treatment for thyroid disease is working.
  • Test a newborn to find out if his or her thyroid gland is working as it should.

How can you prepare for the test?

Talk to your doctor about all your health conditions before the test. For example, tell your doctor about all medicines you take. If you are taking thyroid medicines, tell your doctor when you took your last dose. You may need to stop taking thyroid medicines for a short time before having this test.

What happens during the test?

Blood test

A health professional will take a sample of your blood.

Heel stick

A newborn's heel is pricked with a sharp, short needle (lancet). Then, several drops of blood are collected for the test. Your child may have a tiny bruise where his or her heel was pricked.

What happens after the test?

You can go back to your usual activities right away.

When should you call for help?

Watch closely for changes in your health, and be sure to contact your doctor or nurse call line if you have any questions about this 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 call line 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.

Where can you learn more?

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