Free T4

Last updated: March 25, 2019

What Does Free T4 Mean?

Free T4 is a blood test ordered by medical practitioners to determine how much thyroxine is present in the blood. Thyroxine is supplied by the thyroid gland and attaches to protein that is circulated through the bloodstream. Free T4 is the measure of how much thyroxine is not attached to protein and is indicative of whether the thyroid is functioning properly. The Free T4 test is sometimes called the thyroxine test, free thyroxine test, or free thyroxine index.


WorkplaceTesting Explains Free T4

The Free T4 test is typically ordered to assist in diagnosing medical conditions such as hyperthyroidism, hypothyroidism, thyroid cancer, pituitary gland disorders, Graves disease, female fertility problems, and thyroiditis. Free T4 results should ideally fall within a specific range – results above or below this range may be caused by thyroid disorders. However, there are some medical practitioners who believe that patients may begin to experience thyroid malfunction symptoms even if the Free T4 test results are within the average range. The test is also used to evaluate the effectiveness of treatment of thyroid disorders and thyroid cancer. The thyroid stimulating hormone test (TSH) and Free T3 test may be performed in combination with the Free T4 test. Infants are often subjected to the Free T4 test to catch problems in time to prevent intellectual disabilities caused by hypothyroidism.



thyroxine test, free thyroxine, free thyroxine index

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