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What is a CBC Complete Blood Count Test?

What a CBC Blood Tests Says About Your Health


Updated June 02, 2014

female doctor taking blood sample
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What is a CBC and What Does It Mean?

A CBC, also known as a complete blood count, is a common blood test performed before and after surgery. By measuring the types of blood cells that are in your blood and how many appear, doctors can determine if your blood is normal.

This test also reveals if your blood shows signs of infection, dehydration, anemia, the need for a post-surgery transfusion and more.

Blood can be drawn from a vein, or if you have a special IV inserted for surgery, it may be drawn from that line. Keep in mind that "normal" values can vary slightly based upon the elevation at which you live and the diagnosis listed for high and low levels are not diagnostic. Don't assume anything about your blood tests without speaking to your physician.

Red Blood Cell Count (RBCs): The cells that carry oxygen to the body.

Normal Values:

Men: 4.7 to 6.1 million cells per microliter.

Women: 4.2 to 5.4 million cells per microliter

Low results can indicate blood loss, problems with the bone marrow, leukemia and malnutrition. High results can indicate heart problems, kidney disease, over transfusion and dehydration.

White Blood Cell Count (WBCs): These cells are the infection fighting portion of the blood and play a role in inflammation.

Normal Values: 4,500 to 10,000 cells/mcl

A low count can indicate bone marrow problems, chemical exposure, autoimmune disease, and problems with the liver or spleen. High levels can indicate the presences of tissue damage (burns), leukemia and infectious disease.

Hematocrit: This is the percentage of the blood that is composed of red blood cells.

Normal Values:

Men: 40.7% to 50.3%

Women: 36.1% to 44.3%

Low hematocrit levels can indicate anemia, blood loss, bone marrow problems, malnutrition and more. High levels can indicate dehydration, polycythemia vera, smoking, living at a high altitude and congenital heart disease.

Hemoglobin: Hemoglobin is a protein on red blood cells that carries oxygen.

Normal Values:

Men: 13.8 to 17.2 grams/deciliter

Women: 12.1 to 15.1 grams/deciliter.

Low levels may indicate blood loss or anemia.

Platelet Count (thrombocytes): Platelets are the part of the blood that make the blood clot.

Normal Values: 150,000 to 400,000 per mm3.

Low levels may indicate the person is receiving chemotherapy, hemolytic anemia, the presence of a replacement heart valve, leukemia or a recent blood transfusion. High levels can be caused by anemia, specific types of cancer, polycythemia vera, a recent surgery to remove the spleen and other health issues.


CBC. National Institutes of Health http://www.nlm.nih.gov/medlineplus/ency/article/003642.htm#Normal%20Values

Platelet Count. National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003647.htm

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