The FT4 test is not a definitive test, but an indicative one. Along with T4, T3 is also a major hormone produced by the thyroid gland that helps regulate the body’s metabolism. If you have normal FT4 levels but have symptoms that may be associated with thyroid abnormalities, you may be advised to take the T3 and TSH tests as well to ensure if the thyroid gland is functioning properly. You may also need to have antithyroid antibodies checked for a more accurate diagnosis in case of abnormalities.