Free Triiodothyronine (T3) Test

The free triiodothyronine (T3) test is a blood test that measures the levels of triiodothyronine (T3), a thyroid hormone, in the bloodstream. T3 is the active form of thyroid hormone that plays a crucial role in regulating metabolism, growth, and development in the body. This test specifically measures the unbound or "free" T3 hormone, which is not bound to proteins in the blood. This test provides a more accurate reflection of the active thyroid hormone levels in the body compared to total T3 levels, which include both bound and unbound forms. The free T3 test is primarily used to assess thyroid function, diagnose thyroid disorders, and monitor treatment for thyroid-related conditions. Abnormal levels of free T3 can indicate an overactive thyroid (hyperthyroidism) or an underactive thyroid (hypothyroidism).