Hyperthyroidism, or hyperthyroidism, is classified as mild to moderate to severe and can generally be determined by the level of free thyroxine. In general, the normal range of free thyroxine levels, as measured by chemiluminescence, is 11.5 to 22.7 pmol/L. In mild hyperthyroidism, the level of free thyroxine is measured by the chemiluminescence method. In mild hyperthyroidism, the free thyroxine level is usually 1-1.5 times the upper limit of normal; in moderate hyperthyroidism, the free thyroxine level is usually 1.5-2 times the upper limit of normal; and in severe hyperthyroidism, the free thyroxine level is usually 2-3 times the upper limit of normal. Patients with symptoms related to hyperthyroidism are advised to seek prompt medical attention for a definitive diagnosis and early treatment.