A fever of 38 degrees that does not go down is commonly caused by infectious factors, such as respiratory tract infections caused by viral infections; it is also caused by non-infectious factors, such as rheumatoid immune diseases and central nervous system diseases, which lead to damage to the thermoregulatory center. 1. Infectious factors: the main cause of fever that does not go away. Usually caused by bacterial infection, viral infection, respiratory system, urinary system infection, if not timely anti-infective treatment, or anti-infective treatment is ineffective, the fever will not go away. 2. Non-infectious factors: such as rheumatic immune disease, hyperthyroidism, can cause fever, advanced malignant tumors can also appear fever, central nervous system diseases, such as massive cerebral hemorrhage, caused by the thermoregulatory center is damaged, there will also be a fever does not go down. If you have a fever of more than 38 degrees, you should go to the hospital in time to find out the cause and carry out standardized treatment under the guidance of the doctor.