Complete Blood Count (CBC) Normals and Abnormals

Hematology / Oncology. Gloved hand of technician holding vial of blood and examining blood for clots prior to CBC count and chemotherapy.
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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.

Purpose of Test

Information on a CBC

A CBC provides information on the numbers of the major types of blood cells produced by the bone marrow and released into the circulation.

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 cell present, this test gives "indexes" - parameters in which to understand whether red blood cells are normal in several ways.

  • RBC count - 4.7-6.1 million cells/mcL for men, 4.2-5.4 million cells /mcL for women
  • Hemoglobin - 13.8-17.2 grams/dL for men, 12.1-15.1 grams/dL for women
  • Hematocrit - 40.7-50.3 percent for men, 36.1-44.3 percent for women
  • MCV - 80-95 femtoliter
  • MCH - 27-31 pg/cell
  • MCHC - 32-36 gm/dL

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. 

  • Total WBC - 4,500-10.000 cells/mcL
  • Differential - In a "WBC and diff" the percentage of different white blood cells are listed. These cells include granulocytes and lymphocytes. There are 3 primary types of granulocytes: neutrophils, eosinophils, and basophils.

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.

  • Platelet count 150,000-400,000/dL

During the Test

Interpreting Results

Abnormal Levels and Cancer Treatments

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 during chemotherapy is called bone marrow suppression.​

  • A low level of red blood cells during cancer treatment is called chemotherapy-induced anemia and can occur due to blood loss from surgery as well as the effect of chemotherapy on the production of red blood cells in the bone marrow.
  • A low level of white blood cells during cancer treatment is usually called chemotherapy-induced neutropenia. Neutrophils are just one type of white blood cell but are most important in predisposing someone to infection when numbers are decreased due to chemo.
  • A low level of platelets during cancer treatment is called chemotherapy-induced thrombocytopenia. Platelet levels may also be low during treatment due to bleeding from surgery.
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Article Sources

  • U.S. National Library of Medicine. MedlinePlus. CBC blood test. Updated 08/14/18. https://www.nlm.nih.gov/medlineplus/ency/article/003642.htm