Every afternoon low fever to be alert to tuberculosis, systemic lupus erythematosus and other diseases. 1. Tuberculosis: Tuberculosis is a common infectious disease of the respiratory system, which is caused by Mycobacterium tuberculosis infection. Its symptoms usually manifest as prolonged low afternoon fever, emaciation, night sweats (abnormal sweating after going to sleep and stopping after waking up), coughing, coughing up sputum or sputum with blood in it. 2. Systemic lupus erythematosus: Systemic lupus erythematosus is a kind of diffuse connective tissue disease whose etiology is still unclear, due to the large amount of autoantibodies in the body attacking its own tissues, resulting in damage to many tissues in the body. Typical symptoms include low-grade fever, anorexia, hallucinations, butterfly-shaped erythema on the face, painful nodules on the fingers, and symmetrical swelling and pain in the joints. If low fever occurs frequently in the afternoon, you should go to the hospital as soon as possible and get a clear diagnosis with the help of a doctor to avoid delaying your condition.