Some patients have fever at a fixed time, such as in the afternoon or in the middle of the night, which is mostly due to pathological phenomena, such as tuberculosis, tumors, or abnormalities in the thermoregulatory center, etc.; it may also be due to physiological phenomena, such as nervousness, anxiety, or the result of the temperature imbalance of the surrounding environment, so there is no need to be overly concerned about it. If the fever in the middle of the night is not caused by the above reasons, then we should consult the doctor in time and carry out relevant examinations. Clinically, fever is considered to be a persistent axillary temperature of more than 37.4°C. It is recommended that patients take several measurements at different times of the day and forward the recorded results to the doctor to provide an effective basis for subsequent treatment.