Skip to main content Skip to footer
Book now
Log in Book now

Published: June 6, 2024

What Are Thyroid Function Tests?

Written by QuickMD Publications Team
2 minutes
What Are Thyroid Function Tests?
Thyroid function tests are blood tests that assess how well the thyroid gland in the neck produces thyroid hormone and how much it needs to be stimulated.

What is TSH?

Thyroid Stimulating Hormone (TSH), a key player in thyroid function, is produced in the pituitary gland, located in the head. TSH levels can indicate how well the thyroid is functioning:
  • High TSH Levels: This can indicate that the thyroid gland is having difficulty producing enough thyroid hormone and, therefore, requires higher levels of TSH to stimulate it.
  • Low TSH Levels: This can indicate high thyroid hormone levels, which turn off the pituitary function of producing TSH.
A thyroid screening test generally measures only TSH because it is a very sensitive marker for hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). If TSH levels are abnormal, a free T4 test may be ordered separately, or it may be a “reflex” test, automatically done if TSH levels are abnormal.

What is Free T4?

A free T4 test measures the amount of thyroid hormone in the blood.
  • Low Free T4 Levels (Hypothyroidism): This can result in symptoms such as fatigue, weight gain, cold intolerance, hair thinning, poor concentration, constipation, and dry skin.
  • High Free T4 Levels (Hyperthyroidism): This can result in symptoms such as heat intolerance, fast heartbeat, nervousness, and unexplained weight loss.

What Are Normal Ranges for Thyroid Function Test Results?

  • Normal TSH: 0.5 to 5.0 milli-international units per liter (mIU/L)
  • Normal Free T4: 5.0 to 12.0 micrograms per deciliter (µg/dL)

Where Can I Order a Thyroid Test?

You can order your own thyroid function test online through QuickMD. The test can be collected at any LabCorp location in the US, and one of the QuickMD doctors will contact you with the results.

Get Professional Advice on Thyroid Tests with QuickMD

For personalized medical advice and to order a thyroid function test, QuickMD’s telemedicine urgent care services are here to help. Consult with a QuickMD provider.

Disclaimer

Articles on this website are meant for educational purposes only and are not intended to replace professional medical advice, diagnosis or treatment. Do not delay care because of the content on this site. If you think you are experiencing a medical emergency, please call your doctor immediately or call 911 (if within the United States). This blog and its content are the intellectual property of QuickMD LLC and may not be copied or used without permission.

QuickMD has strict referencing policies and relies on reputable sources, including peer-reviewed research, clinical guidelines, medical organizations, and government and public health agencies, among others. Learn more about how we ensure accuracy in our content by reading our editorial guidelines.

Helpful reading about health & wellness

Learn more