Blood is mainly composed of three types of cells: red cells, white cells, and platelets. In a WBC, the number and types of white blood cells present in the blood are measured. Normal results for a WBC range from 4,500-10,000 white blood cells/mcL (cells per microliter).
The information from the WBC can help diagnose and manage diseases. Many different diseases can cause changes in the numbers of white blood cells. For example, if an infection is present, the number of white blood cells may be higher, or if bone marrow failure is present, the number of white blood cells may be lower.