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A free T4 (FT4) blood test is a laboratory test that measures the level of free thyroxine (T4) in the blood. T4 is a hormone produced by the thyroid gland that plays a key role in regulating metabolism. The FT4 test is used to assess thyroid function and to help diagnose and monitor conditions such as hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). The FT4 test measures the amount of free T4 in the blood, which is the portion of T4 that is not bound to proteins and is available to be used by the body. The test is typically done by drawing a small amount of blood from a vein in the arm and sending it to a laboratory for analysis.
This page is provided for educational and informational purposes only and does not constitute the provision of medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease, and those seeking personal medical advice regarding any of the tests and conditions referenced above are advised to consult with a licensed clinician. Always seek the advice of your qualified health provider regarding a medical condition and do not disregard professional medical advice or delay in seeking it because of any information on this page. If you think you may have a medical emergency, immediately call 911 or go to the nearest urgent care center or hospital.
