Unexplained low-grade fever can usually be examined with blood tests and sedimentation, lung X-ray or CT, and liver function to help determine the cause. 1. Blood test and blood sedimentation: According to the results of white blood cells and neutrophils in the blood test, if they are high, it indicates that the low fever may be caused by bacterial infection, etc. If they are low, it may be caused by viral infection or tuberculosis. If it is low, it may be caused by viral infection or tuberculosis. To determine whether it is tuberculosis, it is necessary to combine with the blood sedimentation test. 2. Lung X-ray or CT: Lung X-ray or CT can generally help to determine whether there is a lung infection, bronchitis, etc. If there is inflammation and infection, the texture of the lungs will become thicker and more disorganized, and small patchy shadows can be seen in both lungs. 3. Liver function: In addition, liver problems may also cause low-grade fever, and liver function tests are needed to see if there are liver problems. It is recommended that patients with unexplained low-grade fever should go to the hospital in time to find out the cause of the problem and follow the doctor’s instructions for symptomatic treatment.