The causes of a body temperature of 35.7°C are mainly in the following areas: age factor, environmental factor, disease factor, and so on. 1. Age factor: the body temperature of the elderly is slightly lower than the standard body temperature, mainly related to the basal metabolic rate. 2. Environmental factors: when the human body is in a lower temperature environment, it will make its own body temperature slightly lower than the normal value, and when out of the environment, it can be restored by itself. 3. Disease factors: such as hypothyroidism, anxiety and depression. (1) Hypothyroidism: The decrease in the basal metabolic rate of these patients leads to a decrease in heat production, resulting in a slightly lower body temperature than normal. (2) Anxiety and depression: mild depression and anxiety can cause instability in the autonomic nervous system, resulting in a lack of coordination in the body’s temperature centers and ultimately causing a slightly lower body temperature. If you exclude environmental factors and age factors, you should consult a doctor in time when your body temperature is abnormal, and follow the doctor’s instructions for treatment.