Free Thyroxine (T4) Test

The free T4 test is a blood test that measures the levels of free thyroxine (T4), a thyroid hormone, in the bloodstream. T4 is an important hormone produced by the thyroid gland that plays a key role in regulating metabolism, growth, and development in the body. This test specifically measures the unbound or "free" T4 hormone, which is not bound to proteins in the blood. This test provides a more accurate assessment of the active thyroid hormone levels in the body compared to total T4 levels, which include both bound and unbound forms. The free T4 test is commonly used to assess thyroid function, diagnose thyroid disorders, and monitor treatment for thyroid-related conditions. Abnormal levels of free T4 can indicate an overactive thyroid (hyperthyroidism) or an underactive thyroid (hypothyroidism).