A body temperature of 35.5°C usually does not belong to the category of low fever, but hypothermia. It is usually related to factors such as the environment the patient is in, hypothyroidism and taking medication. It can be treated by adjusting living habits and taking medication. 1. Environment: If the patient is exposed to low temperature for a long time, it may cause the body temperature to drop to 35.5℃. When the human body is in a cold environment for a long time, the body’s heat production is less than heat dissipation, causing the body temperature to drop. At this time, the patient should promptly get out of the cold environment, pay attention to the cold to keep warm. 2. Hypothyroidism: when suffering from hypothyroidism, the body produces less or insufficient supply of thyroxine, resulting in insufficient heat production, triggering a drop in body temperature, which may fall to 35.5 ℃. You can use levothyroxine sodium tablets, thyroxine tablets, prednisolone acetate according to the doctor’s advice, and usually take more iodine-containing food. 3. Taking drugs: If you take chlorpromazine and other drugs that have an effect on the regulation of body temperature, it can also cause the body temperature to drop to 35.5 ℃. Generally, after stopping the drug, the body temperature will rise again. However, if the temperature does not rise after stopping the medication, you should seek medical attention. A patient’s body temperature of 35.5°C can usually be normalized with the use of warming devices, but if other adverse symptoms develop, prompt medical attention should be sought.