The complete blood count (CBC) remains one of the most common blood tests performed. The CBC includes counts of all three types of blood cells present in a blood sample: red blood cells (RBC), white blood cells (WBC) and platelets (thrombocytes).

The CBC provides important information on the types of blood cells present, and their condition, number and percentage in relation to other cells. The results of a CBC can help diagnose many conditions and diseases. For instance, high WBC levels may indicate a heart attack, infection, an inflammatory disease or leukemia, whereas low levels (leukopenia) can be caused by a wide range of diseases or conditions, including kidney or liver disease, radiation exposure or the presence of a toxic substance in the body.

High RBC levels may indicate a lack of fluid in the body (dehydration), whereas low levels are usually an indicator of anemia. High platelet levels may be due to severe bleeding, infection, strenuous exercise, pregnancy or other factors, whereas low levels (thrombocytopenia) are usually caused by an infection, cancer or a lack of either folic acid or vitamin B-12.

Some medications and dietary supplements may interfere with a CBC. Patients are urged to follow their physician’s orders carefully about how to take their medications before the test in order to ensure its accuracy. There is no need to stop eating or drinking beforehand.