A high ft3 level usually refers to a high level of free triiodothyronine in the body, which often indicates the presence of hyperthyroidism. However, it should only be used as an indicator of hyperthyroidism and should be combined with other thyroid indicators for a definitive diagnosis. When high ft3 is found, thyrotropin should be added. If thyrotropin is also decreased, hyperthyroidism is indicated and further investigations of thyrotropin receptor antibodies, thyroid peroxidase antibodies and thyroglobulin antibodies are needed to understand the cause of hyperthyroidism and to determine the treatment plan. If thyrotropin is normal, high ft3 is often transient and regular review is usually recommended.