The Free T3 test measures the level of free triiodothyronine (T3), a hormone produced by the thyroid gland that plays a significant role in regulating metabolism and energy levels. Unlike total T3, this test focuses specifically on the unbound form of the hormone, which is biologically active. Abnormal Free T3 levels can indicate thyroid dysfunction, impacting energy, weight, and mood. By providing insight into your thyroid hormone status, this test helps you understand your body's metabolic processes and can be a vital part of managing thyroid health.