A complete blood count (CBC) is a blood test done to check the levels of cells in the blood, including the red blood cells, white blood cells, and platelets. Checking a CBC is helpful in making the diagnosis of a large number of medical conditions ranging from infections to the causes of bleeding.
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Purpose of Test
CBC Numbers and Indexes
A CBC gives much more information than the total number of a particular blood cell present.
Red blood cells: In addition to providing just the number of red blood cells present, this test gives “indexes” - parameters in which to understand whether red blood cells are normal in several ways.
White blood cells: A CBC can give the number of white blood cells present in the blood, but a “differential” can also describe what types of white blood cells are present, and if they are in greater or lesser numbers than what would be expected. White blood cells are also called leukocytes.
Platelets: A CBC will give the number of platelets present in the blood. Unfortunately, a CBC can look at numbers, but cannot tell us how “active” the platelets are - someone may still be predisposed to bleeding with a normal platelet count.
Interpreting Results
There are many reasons for doctors to check a CBC. With cancer, a complete blood count (CBC) is often checked at the time of diagnosis, and to follow the levels of blood cells during treatment. Chemotherapy interferes with cell division in rapidly dividing cells such as cancer cells but also affects rapidly dividing cells in the bone marrow. Abnormal levels of cells in the blood duringchemotherapy is called bone marrow suppression.
2 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.NIH U.S. National Library of Medicine.CBC blood test.Fava C, Cattazzo F, Hu ZD, Lippi G, Montagnana M.The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype?Ann Transl Med. 2019;7(20):581. doi:10.21037/atm.2019.09.58Additional ReadingU.S. National Library of Medicine. MedlinePlus. CBC blood test. https://www.nlm.nih.gov/medlineplus/ency/article/003642.htm
2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.NIH U.S. National Library of Medicine.CBC blood test.Fava C, Cattazzo F, Hu ZD, Lippi G, Montagnana M.The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype?Ann Transl Med. 2019;7(20):581. doi:10.21037/atm.2019.09.58Additional ReadingU.S. National Library of Medicine. MedlinePlus. CBC blood test. https://www.nlm.nih.gov/medlineplus/ency/article/003642.htm
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
NIH U.S. National Library of Medicine.CBC blood test.Fava C, Cattazzo F, Hu ZD, Lippi G, Montagnana M.The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype?Ann Transl Med. 2019;7(20):581. doi:10.21037/atm.2019.09.58
NIH U.S. National Library of Medicine.CBC blood test.
Fava C, Cattazzo F, Hu ZD, Lippi G, Montagnana M.The role of red blood cell distribution width (RDW) in cardiovascular risk assessment: useful or hype?Ann Transl Med. 2019;7(20):581. doi:10.21037/atm.2019.09.58
U.S. National Library of Medicine. MedlinePlus. CBC blood test. https://www.nlm.nih.gov/medlineplus/ency/article/003642.htm
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