. FT3 is used to evaluate the function of the thyroid gland, which regulates metabolism, energy production, and overall growth and development.
. FT3 measures the unbound, active form of T3. The FT3 is the form that the body uses directly to regulate various physiological processes.
. FT3, along with other TFT, is used to diagnose thyroid dysfunction (e.g., hyperthyroidism, hypothyroidism), to monitor treatment for thyroid disorders (especially in those taking thyroid hormone replacement or anti-thyroid medications), to evaluate conditions such as Graves' disease, Hashimoto's thyroiditis, or thyroid nodules, and to detect non-thyroidal illness (conditions affecting thyroid hormone levels independently of thyroid function).