The patient’s fever and low white blood cells may be caused by the following factors: 1, the patient’s fever leads to low white blood cells, which may be caused by viral infections in the body, the upper respiratory tract infection virus will lead to fever phenomenon, some patients will appear low white blood cells. 2, may be the patient after the fever taking antipyretic drugs, such as acetaminophen, aspirin, the patient’s body will also bring certain side effects, low white blood cells is the more common side effects. 3. Some patients have a low immune system and may have a fever that leads to low white blood cells after a viral infection. When the patient has symptoms, he should go to the hospital for examination and treatment after the cause is clear.