The sudden increase in body temperature may be caused by physiological factors or pathological factors, the body’s heat production and heat dissipation are subject to the deployment of the thermoregulatory center, clinical examination of the patient’s body temperature and observation of changes. It is important for the diagnosis or prognosis of the disease. Under normal circumstances, that is, the physiological state of human body temperature will also fluctuate, generally not more than 1 ℃ difference, generally in the afternoon, the evening body temperature is high or eating, exercise, drinking water, women’s premenstrual period, pregnancy body temperature will be slightly higher. Generally the afternoon body temperature is the highest, the early morning body temperature is the lowest, the body temperature is higher than the normal body temperature is called fever, more than 37.5 ℃ is called hypothermia.