Overview & Description

A CBC, also called a complete blood count, is a screening test used todiagnose and manage many diseases. A CBC measures the status of importantfeatures of the blood, including the following:

  • mean corpuscular hemoglobin, which is also called MCH
  • mean corpuscular hemoglobin concentration, which is also called MCHC
  • mean corpuscular volume, also called MCV
  • number of platelets
  • number of red blood cells, also called RBCs
  • number of white blood cells, also called WBCs
  • percentage of blood composed of cells, called the hematocrit
  • total amount of hemoglobin in the blood
  • Who is a candidate for the test?

    A CBC is a part of routine blood testing done with physical examinations.It is also used to help diagnose many disorders, including problems with yourblood, heart, kidneys, and nutritional status.

    How is the test performed?

    A blood sample is taken from a vein on your forearm or hand. First, the skinover your vein is cleaned with an antiseptic. Next, a strong rubber tube, called a tourniquet,is wrapped around your upper arm. This enlarges the veins in your lower arm by restrictingblood flow through them. A fine needle is gently inserted into a vein, and the tourniquetis removed. Blood flows from your vein through the needle and into a syringeor vial. After the needle is withdrawn, the puncture site is covered with a bandage for ashort time. This helps stop or prevent bleeding at the site.

    Preparation & Expectations

    What is involved in preparation for the test?

    Request specific instructions from your doctor.

    Results and Values

    What do the test results mean?

    Normal values are as follows:

  • RBC (value changes with altitude): Male, 4.7-6.1 million cells/mcl; female,4.2-5.4 million cells/mcl
  • WBC: 4,500-10,000 cells/mcl
  • hematocrit (varies with altitude): Male, 40.7-50.3%; female, 36.1-44.3%
  • hemoglobin (varies with altitude): Male, 13.8-17.2 gm/dcl; female, 12.1-15.1gm/dcl
  • MCV: 80-95 femtoliter
  • MCH: 27-31 pg/cell
  • MCHC: 32-36 gm/dl
  • Abbreviations:

  • cells/mcl = cells per microliter
  • gm/dl = grams per deciliter
  • pg/cell = picograms per cell
  • Abnormally high numbers of red blood cells may be a sign of the following:

  • congenital heart disease,which is a heart condition that you are born with
  • cor pulmonale,which means a condition in which the right lower part of the heart becomes swollen
  • dehydration,which is a lack of fluid in the body that can occur with conditions such as severe diarrhea
  • kidney disease with high levels of erythropoietin, a hormone producedin the kidney
  • low oxygen tension in the blood
  • pulmonary fibrosis, which is a hardening of the lung tissue that can make hard for you to breathe
  • Abnormally low numbers of red blood cells, or anemia, may be a sign of the following:

  • blood loss
  • bone marrow failure
  • erythropoietin deficiency,which occurs when the kidney does not produce enough of the hormone
  • hemolysis, which is the destruction of RBCs from a transfusion reaction
  • hemorrhage, which is a loss of blood
  • leukemia,which is cancer of the blood and bone marrow
  • malnutrition
  • multiple myeloma,a cancer of the bone marrow
  • overhydration, which means absorption of too much fluid in your body tissues
  • Abnormally low numbers of white blood cells may be a sign of the following:

  • bone marrow failure
  • collagen-vascular diseases, which are any diseases that cause the small blood vessels and tissue to swell
  • exposure to radiation
  • liver or spleen disease
  • the presence of substances toxic to cells
  • High numbers of white blood cells may point to the possible presence of the following:

  • emotional or physical stress
  • infections
  • inflammatory diseases
  • leukemia
  • tissue damage
  • High hematocrit may be a sign of the following:

  • burns
  • dehydration
  • diarrhea
  • eclampsia,a serious condition involving high blood pressure, protein in the urine and swelling of yourface and hands during pregnancy that can lead to seizures and coma
  • erythrocytosis, which is an unhealthy rise in the number of red blood cells
  • polycythemia vera,which is an increase in the cell mass or red blood cell levels in your blood
  • shock
  • Low hematocrit may indicate that one of these conditions is present:

  • anemia
  • blood loss
  • bone marrow failure
  • hemolysis, which is the separation of hemoglobin, the oxygen-carrying component of redblood cells, from the red blood cells
  • leukemia
  • malnutrition
  • multiple myeloma
  • overhydration
  • rheumatoid arthritis,a long-term disease in which the connective tissue is destroyed
  • specific nutritional deficiency
  • Low hemoglobin values may indicate:

  • anemia
  • blood loss
  • Article type: xmedgeneral