A complete blood count (CBC) is a test that measures the levels of red blood cells (RBC), white blood cells (WBC) and platelets in a person’s blood. A CBC is one of the most common blood tests performed today. It can provide important information on the types of blood cells present, 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. In contrast, low levels can be caused by 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), exposure to high altitude or some primary blood diseases, whereas low levels are usually an indicator of anemia. Anemia may be a sign of several cancers including colorectal, stomach and lymphomas.

High platelet levels may be due to severe bleeding, infection, strenuous exercise, pregnancy or other factors. An indvidual who has low platelet levels may have been affected by an infection or a lack of either folic acid or vitamin B–12. Certain primary benign blood diseases or blood cancers can also cause high or low levels.

CBC is typically performed on cancer patients undergoing chemotherapy or radiation therapy to determine if the treatments have affected bone marrow cell production. In addition, a CBC can help detect diseases such as leukemia or multiple myeloma.

Some medications may affect the results of a CBC. Patients are urged to carefully follow their physician’s orders about how to take their medications before the test in order to ensure its accuracy. There is no need to stop eating or drinking before undergoing a CBC.

CBC tests can be performed in a number of different settings, including a physician’s office, hospital, laboratory or outpatient clinic. They are relatively quick, performed with little pain and can yield valuable information about an individual’s health.