Unexplained low fever when the cause can not be found generally only need symptomatic treatment, under the guidance of the doctor to use physical antipyretic or non-steroidal drugs to reduce fever, do not need to use other drugs. The normal body temperature of the human body is about 36~37℃, when the body temperature is 37.3~38℃ it is called hypothermia, which is a more common clinical disease. According to its etiology, it can be divided into physiological hypothermia and pathologic hypothermia (e.g., infection). Common diseases that cause low fever include tuberculosis, chronic pyelonephritis, hyperthyroidism, rheumatic fever, etc. Treatment varies according to the cause. For unexplained low-grade fever, patients should firstly cooperate with the examination under the guidance of the doctor to clarify the cause of the disease. If the cause of the disease is still unclear after several examinations, but the low-grade fever persists and there are no other symptoms, symptomatic treatment can be taken first, such as adopting physical cooling or taking non-steroidal antipyretic drugs, and then continue to observe the changes of the disease. The best treatment for patients with low fever is still to use drugs according to the disease, but there are many causes of fever, it is difficult to find the specific cause of all of them, there is an unknown cause of fever, we should listen to the doctor’s advice, in the case of perfecting the necessary tests, but still can not be clarified, we need to observe, and at the same time, regular review, to avoid the indiscriminate use of drugs.