Normally, a 3-month-old baby’s body temperature of 37.5°C is considered a low-grade fever. Measuring your baby’s body temperature is most commonly done with an axillary temperature, and a normal axillary temperature is between 36-37°C. Usually a temperature of 37.3-38°C is considered a low-grade fever. So if a 3-month-old baby’s axillary body temperature is 37.5 ℃ is considered a fever, and belongs to the low fever. However, 3-month-old baby thermoregulation ability is poor, easily disturbed by external factors, such as high-temperature environment, baby crying, etc., may also cause the baby’s body temperature rises to 37.5 ℃, but if you leave the high-temperature environment, the baby’s mood stabilized, remove the interference and then retest the temperature can be restored to normal. If the temperature can not return to normal, repeated measurement of body temperature, is still 37.5 ℃, need to consult a doctor in time to rule out disease factors, such as colds, viral encephalitis and so on. And for the unexplained low fever can not be indiscriminate use of drugs, so as not to cover up the development of the disease, can be through physical methods to help the baby cool down, such as warm water baths.