Higher free thyroxine (FT4) suggests that there may be thyroid function abnormalities, of which hyperthyroidism is more common, affecting the patient’s daily life, and in severe cases, inducing thyroid crisis, which may threaten the patient’s life. Free thyroxine is a physiologically active form of thyroxine, which can directly reflect the thyroid function. Elevated indexes are mostly seen in patients with hyperthyroidism, which can cause a series of symptoms such as palpitations (accelerated heartbeat, often accompanied by panic), fatigue, weight loss, diarrhea, insomnia and other symptoms, which will affect the patient’s daily life, and can be relieved after standardized treatment. However, thyroid crisis may be triggered by unstandardized treatment or stress factors such as mental stimulation, which requires immediate rescue treatment or may threaten the patient’s life. It is recommended to go to the hospital and ask the doctor to make a judgment when there is a high level of free thyroxine.