It is unlikely that a fever of 39 degrees in adults will go down on its own. You need to take ibuprofen or acetaminophen to reduce the fever, and treat the cause of the illness at the same time. 39 degrees is a high fever, the possibility of self-reduction of fever is unlikely, because 39 degrees high fever has exceeded the body’s self-regulation range, need to be actively treated before the fever can be reduced. At the same time, if you don’t take measures to reduce fever in time, it will affect the normal metabolism of the body, which in turn affects the normal function of the body, so you need to take treatment in time. Patients with high fever, you can take oral ibuprofen or acetaminophen and other antipyretics, but also through the physical cooling methods to assist in reducing fever, but also need to address the cause of the treatment. If the symptoms of high fever are not relieved, or accompanied by other symptoms, you should go to the hospital in time to clarify the cause of the disease and then give targeted treatment.