Complete Blood Count (CBC)

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Complete Blood Count (CBC) gives important information about all the kinds and number of blood cells in the body. These cells include red blood cells, white blood cells , hemoglobin, and platelets. This test is used to evaluate your over all health and to diagnose diseases and medical conditions. Abnormal increase and decrease in these cells may indicate an underlying problem.


Evaluate your overall health : This test may be required as part of a routine medical checkup. This is to monitor your health and screen for a lot of diseases and disorders.

Diagnose a medical problem: If you are experiencing symptoms such as fatigue, weakness, bleeding and so on, your doctor will order a CBC. This will help him know the cause of your symptoms.

Monitor a medical condition : If you’ve been diagnosed with a disease that affects your blood count such as thalassemia, your doctor will use a CBC to monitor your condition.

Monitor a treatment : CBC is used to monitor treatment that may affect your blood count.


There are no special preparations for this test. You can eat or drink normally for this test. If your blood sample will be used for other tests, you may be required to fast before the test. However, your doctor will give you instructions if need be.


A needle is inserted into your vein to take a blood sample. The blood is then sent to the lab for analysis.


There is very little risk associated with having your blood drawn. Some of the possible risks include

  • fainting
  • excessive bleeding
  • accumulation of blood under the skin – hematoma
  • infection


Normal results for adults

Red blood cell count Male: 4.32-5.72 trillion cells/L*          (4.32-5.72 million cells/mcL**) Female: 3.90-5.03 trillion cells/L             (3.90-5.03 million cells/mcL)
Hemoglobin Male: 13.5-17.5 grams/dL***             (135-175 grams/L) Female: 12.0-15.5 grams/dL             (120-155 grams/L)
Hematocrit Male: 38.8-50.0 percent Female: 34.9-44.5 percent
White blood cell count 3.5-10.5 billion cells/L             (3,500 to 10,500 cells/mcL)
Platelet count 150-450 billion/L             (150,000 to 450,000/mmol****)

* L = liter ** mcL = microliter *** dL = deciliter **** mmol = micromole

Source : Mayo Foundation. Accessed January 9, 2014

Abnormal results

A high RBC or hematocrit may be due to

  • dehydration
  • polycythemia vera
  • smoking
  • low oxygen level in the blood due to heart or lung disease

A lower than normal RBC may indicate

  • blood loss
  • leukemia and other blood cancers
  • hemolysis
  • deficient in iron, folate, vitamin B12 or vitamin B6
  • multiple myeloma

Lower than normal white blood cells is called  leukopenia and can be caused by the following

  • autoimmune disease
  • bone marrow problems or cancer
  • liver or spleen disease

Higher than normal white blood cells mean

  • inflammatory diseases such as rheumatoid arthritis
  • infectious disease
  • leukemia

Low hemoglobin may mean anemia or blood loss.

Lower or higher than normal platelet count may indicate an underlying medical condition or effects of medications. Further testing is however needed to diagnose the problem.

Blood test : Compelete blood count. The Nemours Foundation. Accessed January 9,2014

CBC. National Library of Medicine. MedlinePlus. Accessed January 9, 2014

Complete blood count CBC. Mayo Foundation. Accessed January 9, 2014

The American Heritage® Stedman’s Medical Dictionary. Retrieved January 2014 from website.

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