Free T4

Supporting to diagnose and monitor thyroid disease and conditions

Free T4 test measures the level of the hormone thyroxine (T4) in your blood. The thyroid gland produces T4 in response to thyroid-stimulating hormone (TSH). T4 is found in the body in two forms: free T4 and bound T4. A total T4 test can measure the total amount of both free and bound T4 in the blood, while a free T4 test will only measure the amount of T4 in its free form, so it more accurately reflects how the thyroid gland is functioning.