A fever blood test is performed after a hospital visit and a lab order is issued. If the fever is caused by an infectious disease, there are usually abnormalities in the blood count, such as elevated total white blood cells, elevated neutrophils, or abnormal changes in lymphocyte count. The interpretation of specific laboratory results needs to be analyzed and judged in the context of the patient’s overall status. Therefore, in case of clinical fever, routine blood tests should be performed in a timely manner, and other relevant screening tests should be performed in conjunction with the overall condition to clarify the diagnosis and provide targeted treatment.