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Complete blood count (CBC) test

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What is a Complete blood count (CBC) test?

The CBC test measures the important components of blood and offers a general picture of a person’s health. It is also known as full blood test. This panel of tests is a routine screening test that not only helps to diagnose various blood disorders, but also underlying infection and diseases within the body. The parameters tested, in general, are related to the three main components of blood- white blood cells, red blood cells and platelets:

  • Total White blood cells (leukocyte count): total count in given volume of blood.
  • Differential White blood cells: the percentage of the various types of white blood cells, namely, neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
  • Red blood cells count: indicates number of red blood cells in a given volume of blood.
  • Red blood cell indices: MCV (mean corpuscular volume) size of RBC, MCH (mean corpuscular hemoglobin) how much hemoglobin in RBC on an average, MCHC (mean corpuscular hemoglobin concentration) hemoglobin concentration in RBC on an average.
  • Hemoglobin: quantity of hemoglobin that is present in the bloodstream.
  • Hematocrit(PCV): volume taken by RBC in blood.
  • Platelet count: total count of platelets in a given volume of blood.

Why is it conducted?

The complete blood count test is frequently carried out as part of a general physical examination. Almost every condition of the body has some effect on the blood of the person and this test helps to understand the overall health of the individual.

Who should go for it?

  • It may be ordered when certain infections or diseases are suspected as changes in the various parameters help in diagnosis.
  • Persons who are suffering from fatigue, easy bruising, feeling of weakness or any kind of fever are advised to have this test.
  • In the case of certain blood disorders, a CBC helps to diagnose and monitor the efficacy of the treatment being given.
  • This test is also advised before surgery to check for general health.
  • It is also carried out to gauge blood loss in case of abnormal bleeding.


This is a routine blood test that requires no special preparation or precautions beforehand. Blood will be drawn by a technician from your arm.

Interpretation of results

Total White blood cells:

4,300 and 10,800 cells/cmm or otherwise expressed as 4.3 to 10.8 x 109 cells per liter.

Higher levels can indicate infection, inflammation or even leukemia. Low values may be due to bone marrow problems or autoimmune diseases.

Differential White blood cells:

The normal range for neutrophils is 54-62 %, lymphocytes is 20- 40 %, monocytes is 3-7 %, eosinophils is 1-4 %, basophils is < 1 %.

Raised levels may indicate : neutrophils - bacterial or acute viral infection, lymphocytes-viral, CLL, monocytes- bacterial, Tuberculosis, eosinophils – parasites in the body, asthma and basophils- bone marrow disorders.

Since each WBC has specific roles in fighting infection, this yields important information regarding the possible cause of inflammation or disease.

Red blood cells count:

the normal levels are from 4.2 to 5.9 x 1012 cells per liter.

Low count indicates anemia due to any cause, high count may lead to clumping and thereby cause blockage.

Red blood cell indices:

MCV: 80 - 100 femtoliters, MCH: 27 - 32 picograms, MCHC: 32% -36%.

These help to find out the possible causes of anemia.


Normal ranges for males are between 13g/dL to 18g/dL and 12g/dL to 16g/dL for females.

It reflects the oxygen carrying capacity of blood.

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45% - 52% for males and 37% - 48% for females.

It indicates anemia or excess RBC volume.

Platelet count:

150 to 400 x 109/liter.

Low count may increase clotting time. High may cause clot formation in arteries.

It is important to remember that certain conditions, like an enlarged spleen or pregnancy can cause changes in blood components.

Written by: Nandita tripati

Date last updated: January 10, 2015