High total thyroxine can be caused by hyperthyroidism, but it can also be caused by changes in thyroid hormone levels due to infections, pregnancy, and other factors. Total thyroid hormone is a very important indicator of thyroid function, and elevated levels are usually seen in hyperthyroidism. Hyperthyroidism is mainly characterized by symptoms such as fatigue, low-grade fever, irritability, cardiac arrhythmia, weight loss, hyperphagia, and diarrhea. Combined with other thyroid hormones, thyroid-stimulating hormone levels, and thyroid autoantibodies, further diagnostic evaluation is possible. However, it should be noted that pregnancy, liver abnormalities, infections, immunization and other factors may affect the total thyroxine level, and the diagnosis should be confirmed in conjunction with other relevant tests. Prompt medical attention is recommended for high total thyroxine.