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CBC blood test

Complete blood count

 

A complete blood count (CBC) test measures the following:

  • The number of red blood cells (RBC count)
  • The number of white blood cells (WBC count)
  • The total amount of hemoglobin in the blood
  • The fraction of the blood composed of red blood cells (hematocrit)

The CBC test also provides information about the following measurements:

  • Average red blood cell size (MCV)
  • Hemoglobin amount per red blood cell (MCH)
  • The amount of hemoglobin relative to the size of the cell (hemoglobin concentration) per red blood cell (MCHC)

The platelet count is also usually included in the CBC.

How the Test is Performed

 

A blood sample is needed.

 

How to Prepare for the Test

 

There is no special preparation needed.

 

How the Test will Feel

 

When the needle is inserted to draw blood, you may feel moderate pain. Some people feel only a prick or stinging. Afterward there may be some throbbing or slight bruising. This soon goes away.

 

Why the Test is Performed

 

A complete blood count (CBC) is a commonly performed lab test. It can be used to detect or monitor many different health conditions. Your health care provider may order this test:

  • As part of a routine check-up
  • If you are having symptoms, such as fatigue, weight loss, fever or other signs of an infection, weakness, bruising, bleeding, or any signs of cancer
  • When you are receiving treatments (medicines or radiation) that may change your blood count results
  • To monitor a chronic health problem that may change your blood count results, such as chronic kidney disease

 

Normal Results

 

Blood counts may vary with altitude. In general, normal results are:

RBC count:

  • Male: 4.7 to 6.1 million cells/mcL (4.7 to 6.1 x 10^12/L)
  • Female: 4.2 to 5.4 million cells/mcL ( 4.2 to 5.4 x 10^12/L)

WBC count:

  • 4,500 to 10,000 cells/mcL (4.5 to 11.0 x10^9/L)

Hematocrit:

  • Male: 40.7% to 50.3% (0. 41 to 0.50)
  • Female: 36.1% to 44.3% (0.36 to 0.44)

Hemoglobin:

  • Male: 13.8 to 17.2 gm/dL (138 to 172 g/L)
  • Female: 12.1 to 15.1 gm/dL (121  to 151 g/L)

Red blood cell indices:

  • MCV: 80 to 95 femtoliter
  • MCH: 27 to 31 pg/cell
  • MCHC: 32 to 36 gm/dL (320 to 360 g/L)

Platelet count:

  • 150,000 to 450,000/dL (150 to 450 x 10^9/L)

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

 

What Abnormal Results Mean

 

High RBC, hemoglobin, or hematocrit may be due to:

  • A lack of enough water and fluids, such as from severe diarrhea, excessive sweating, or water pills used to treat high blood pressure
  • Kidney disease with high erythropoietin production
  • Low oxygen level in the blood for a long time, most often due to heart or lung disease
  • Polycythemia vera
  • Smoking

Low RBC, hemoglobin, or hematacrit is a sign of anemia, which can result from:

  • Blood loss (either sudden, or from problems such as heavy menstrual periods over a long time)
  • Bone marrow failure (for example, from radiation, infection, or tumor)
  • Breakdown of red blood cells (hemolysis)
  • Cancer and cancer treatment
  • Certain long-term (chronic) medical conditions, such as chronic kidney disease, ulcerative colitis, or rheumatoid arthritis
  • Leukemia
  • Long-term infections such as hepatitis
  • Poor diet and nutrition, causing too little iron, folate, vitamin B12, or vitamin B6
  • Multiple myeloma

A lower than normal white blood cell count is called leukopenia. A decreased WBC count may be due to:

  • Alcohol abuse and liver damage
  • Autoimmune diseases (such as systemic lupus erythematosus)
  • Bone marrow failure (for example, due to infection, tumor, radiation, or fibrosis)
  • Chemotherapy medicines used to treat cancer
  • Disease of the liver or spleen
  • Enlarged spleen
  • Infections caused by viruses, such as mono or AIDS
  • Medications

A high WBC count is called leukocytosis. It can result from:

  • Certain medicines, such as corticosteroids
  • Infections
  • Diseases such as lupus,rheumatoid arthritis or allergy
  • Leukemia
  • Severe emotional or physical stress
  • Tissue damage (such as from burns or a heart attack)

A high platelet count may be due to:

  • Bleeding
  • Diseases such as cancer
  • Iron deficiency
  • Problems with the bone marrow

A low platelet count may be due to:

  • Anemia (various types)
  • Disorders where platelets are destroyed
  • Pregnancy
  • Enlarged spleen
  • Bone marrow failure (for example, due to infection, tumor, radiation, or fibrosis)
  • Chemotherapy medicines used to treat cancer

 

Risks

 

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)

 

Considerations

 

RBCs transport hemoglobin which, in turn, carries oxygen. The amount of oxygen received by body tissues depends on the amount and function of RBCs and hemoglobin.

WBCs are mediators of inflammation and the immune response. There are various types of WBCs that normally appear in the blood:

  • Neutrophils (polymorphonuclear leukocytes)
  • Band cells (slightly immature neutrophils)
  • T-type lymphocytes (T cells)
  • B-type lymphocytes (B cells)
  • Monocytes
  • Eosinophils
  • Basophils

 

 

References

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 30.

 
  • Red blood cells, sickle cell

    Red blood cells, sickle cell - illustration

    Sickle cell anemia is an inherited blood disease in which the red blood cells produce abnormal pigment (hemoglobin). The abnormal hemoglobin causes deformity of the red blood cells into crescent or sickle-shapes, as seen in this photomicrograph.

    Red blood cells, sickle cell

    illustration

  • Megaloblastic anemia - view of red blood cells

    Megaloblastic anemia - view of red blood cells - illustration

    This picture shows large, dense, oversized, red blood cells (RBCs) that are seen in megaloblastic anemia. Megaloblastic anemia can occur when there is a deficiency of vitamin B-12.

    Megaloblastic anemia - view of red blood cells

    illustration

  • Red blood cells, tear-drop shape

    Red blood cells, tear-drop shape - illustration

    This photomicrograph shows one of the abnormal shapes that red blood cells (RBCs) may assume, a tear-drop shape. Normally, RBCs are round.

    Red blood cells, tear-drop shape

    illustration

  • Red blood cells, normal

    Red blood cells, normal - illustration

    This photomicrograph shows normal red blood cells (RBCs) as seen in the microscope after staining.

    Red blood cells, normal

    illustration

  • Red blood cells, elliptocytosis

    Red blood cells, elliptocytosis - illustration

    Elliptocytosis is a hereditary disorder of the red blood cells (RBCs). In this condition, the RBCs assume an elliptical shape, rather than the typical round shape.

    Red blood cells, elliptocytosis

    illustration

  • Red blood cells, spherocytosis

    Red blood cells, spherocytosis - illustration

    Spherocytosis is a hereditary disorder of the red blood cells (RBCs), which may be associated with a mild anemia. Typically, the affected RBCs are small, spherically shaped, and lack the light centers seen in normal, round RBCs.

    Red blood cells, spherocytosis

    illustration

  • Red blood cells, multiple sickle cells

    Red blood cells, multiple sickle cells - illustration

    Sickle cell anemia is an inherited disorder in which abnormal hemoglobin (the red pigment inside red blood cells) is produced. The abnormal hemoglobin causes red blood cells to assume a sickle shape, like the ones seen in this photomicrograph.

    Red blood cells, multiple sickle cells

    illustration

  • Basophil (close-up)

    Basophil (close-up) - illustration

    Basophils are a specific type of white blood cell. These cells are readily stained with basic dyes (this is where the name comes from). Note the dark grains inside the cellular fluid (cytoplasm) of this basophil. Basophils make up only a small portion of the number of white blood cells but are important parts of the body's immune response. They release histamine and other chemicals that act on the blood vessels when the immune response is triggered.

    Basophil (close-up)

    illustration

  • Malaria, microscopic view of cellular parasites

    Malaria, microscopic view of cellular parasites - illustration

    Malarial parasites are visible within the red blood cells. They are stained a dark bluish color.

    Malaria, microscopic view of cellular parasites

    illustration

  • Malaria, photomicrograph of cellular parasites

    Malaria, photomicrograph of cellular parasites - illustration

    Malaria is a disease caused by parasites. This picture shows dark orange-stained malaria parasites inside red blood cells (a) and outside the cells (b). Note the large cells that look like targets; it is unknown how these target cells are related to this disease.

    Malaria, photomicrograph of cellular parasites

    illustration

  • Red blood cells, sickle cells

    Red blood cells, sickle cells - illustration

    These crescent or sickle-shaped red blood cells (RBCs) are present with Sickle cell anemia, and stand out clearly against the normal round RBCs. These abnormally shaped cells may become entangled and block blood flow in the small blood vessels (capillaries).

    Red blood cells, sickle cells

    illustration

  • Red blood cells, sickle and pappenheimer

    Red blood cells, sickle and pappenheimer - illustration

    This photomicrograph of red blood cells (RBCs) shows both sickle-shaped and Pappenheimer bodies.

    Red blood cells, sickle and pappenheimer

    illustration

  • Red blood cells, target cells

    Red blood cells, target cells - illustration

    These abnormal red blood cells (RBCs) resemble targets. These cells are seen in association with some forms of anemia, and following the removal of the spleen (splenectomy).

    Red blood cells, target cells

    illustration

  • Formed elements of blood

    Formed elements of blood - illustration

    Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

    Formed elements of blood

    illustration

  • Complete blood count - series

    Complete blood count - series

    Presentation

    • Red blood cells, sickle cell

      Red blood cells, sickle cell - illustration

      Sickle cell anemia is an inherited blood disease in which the red blood cells produce abnormal pigment (hemoglobin). The abnormal hemoglobin causes deformity of the red blood cells into crescent or sickle-shapes, as seen in this photomicrograph.

      Red blood cells, sickle cell

      illustration

    • Megaloblastic anemia - view of red blood cells

      Megaloblastic anemia - view of red blood cells - illustration

      This picture shows large, dense, oversized, red blood cells (RBCs) that are seen in megaloblastic anemia. Megaloblastic anemia can occur when there is a deficiency of vitamin B-12.

      Megaloblastic anemia - view of red blood cells

      illustration

    • Red blood cells, tear-drop shape

      Red blood cells, tear-drop shape - illustration

      This photomicrograph shows one of the abnormal shapes that red blood cells (RBCs) may assume, a tear-drop shape. Normally, RBCs are round.

      Red blood cells, tear-drop shape

      illustration

    • Red blood cells, normal

      Red blood cells, normal - illustration

      This photomicrograph shows normal red blood cells (RBCs) as seen in the microscope after staining.

      Red blood cells, normal

      illustration

    • Red blood cells, elliptocytosis

      Red blood cells, elliptocytosis - illustration

      Elliptocytosis is a hereditary disorder of the red blood cells (RBCs). In this condition, the RBCs assume an elliptical shape, rather than the typical round shape.

      Red blood cells, elliptocytosis

      illustration

    • Red blood cells, spherocytosis

      Red blood cells, spherocytosis - illustration

      Spherocytosis is a hereditary disorder of the red blood cells (RBCs), which may be associated with a mild anemia. Typically, the affected RBCs are small, spherically shaped, and lack the light centers seen in normal, round RBCs.

      Red blood cells, spherocytosis

      illustration

    • Red blood cells, multiple sickle cells

      Red blood cells, multiple sickle cells - illustration

      Sickle cell anemia is an inherited disorder in which abnormal hemoglobin (the red pigment inside red blood cells) is produced. The abnormal hemoglobin causes red blood cells to assume a sickle shape, like the ones seen in this photomicrograph.

      Red blood cells, multiple sickle cells

      illustration

    • Basophil (close-up)

      Basophil (close-up) - illustration

      Basophils are a specific type of white blood cell. These cells are readily stained with basic dyes (this is where the name comes from). Note the dark grains inside the cellular fluid (cytoplasm) of this basophil. Basophils make up only a small portion of the number of white blood cells but are important parts of the body's immune response. They release histamine and other chemicals that act on the blood vessels when the immune response is triggered.

      Basophil (close-up)

      illustration

    • Malaria, microscopic view of cellular parasites

      Malaria, microscopic view of cellular parasites - illustration

      Malarial parasites are visible within the red blood cells. They are stained a dark bluish color.

      Malaria, microscopic view of cellular parasites

      illustration

    • Malaria, photomicrograph of cellular parasites

      Malaria, photomicrograph of cellular parasites - illustration

      Malaria is a disease caused by parasites. This picture shows dark orange-stained malaria parasites inside red blood cells (a) and outside the cells (b). Note the large cells that look like targets; it is unknown how these target cells are related to this disease.

      Malaria, photomicrograph of cellular parasites

      illustration

    • Red blood cells, sickle cells

      Red blood cells, sickle cells - illustration

      These crescent or sickle-shaped red blood cells (RBCs) are present with Sickle cell anemia, and stand out clearly against the normal round RBCs. These abnormally shaped cells may become entangled and block blood flow in the small blood vessels (capillaries).

      Red blood cells, sickle cells

      illustration

    • Red blood cells, sickle and pappenheimer

      Red blood cells, sickle and pappenheimer - illustration

      This photomicrograph of red blood cells (RBCs) shows both sickle-shaped and Pappenheimer bodies.

      Red blood cells, sickle and pappenheimer

      illustration

    • Red blood cells, target cells

      Red blood cells, target cells - illustration

      These abnormal red blood cells (RBCs) resemble targets. These cells are seen in association with some forms of anemia, and following the removal of the spleen (splenectomy).

      Red blood cells, target cells

      illustration

    • Formed elements of blood

      Formed elements of blood - illustration

      Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

      Formed elements of blood

      illustration

    • Complete blood count - series

      Presentation

    A Closer Look

     

    Talking to your MD

     

      Self Care

       

      Tests for CBC blood test

       

       

      Review Date: 11/26/2014

      Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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