What is complete blood count used for?

A complete blood count test is used to detect abnormalities in the blood. Any deviations in number, size, or maturity from what is considered the normal range may be indicative of an infection. For example, an abnormal increase in the number of white blood cells may be a sign of an infection. If the CBC shows a higher number of immature white blood cells, it may indicate leukemia. Abnormally low hemoglobin levels are linked to anemia or sickle cell disease.