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How to use white blood cell tests

by — Last updated: 2017-08-17 in Cardiovascular Disorders and Diseases
Reviewed by Medical Team — 2017-06-14

Table of Contents

White blood cells have nuclei, participate in protecting the body from infection, and consist of lymphocytes and monocytes with relatively clear cytoplasm, and three types of granulocytes, whose cytoplasm has granules.
Conditions or medications that weaken the immune system, such as a HIV infection or chemotherapy, cause a decrease in white blood cell count, so the white blood cell (WBC) count detects dangerously low numbers of these cells. [9]

The WBC count helps to suggest the presence of an infection or leukemia. It is also used to help monitor the body’s response to various treatments and to monitor bone marrow function as well. [9]

Definition Of White Blood Cell Count

A white blood cell count or leukocyte count is, simply said,  the number of white blood cells in the blood. The doctor will usually measure WBC as part of the CBC, or complete blood count. White blood cells are the infection-fighting cells in the blood and are distinct from the red oxygen-carrying blood cells, known as erythrocytes.

All the types of white blood cells are reflected in the white blood cell count:

  • The normal range for the white blood cell count varies between laboratories but is usually between 4,300 and 10,800 cells per cubic millimeter of blood. [10]
This can also be referred to as the leukocyte count and expressed in international units as 4.3-10.8 x 109 cells per liter. A WBC count below 4300 is below normal.

A low white blood cell count is termed leucopenia, and a high white blood cell count is termed leukocytosis.

What Does The WBC Test Result Mean?

Since reference values are dependent on many factors including [12]:

  • Patient age
  • Gender
  • Sample population
  • Test method 

numeric test results have different meanings in different labs.

Your lab report should include the specific reference range for your test and you should discuss your test results with your doctor.

  • An elevated number of white blood cells (leukocytosis) can result from bacterial infections, inflammation, leukemia, trauma, or stress.
  • A decreased WBC count (leucopenia) can result from many different situations, such as chemotherapy, radiation therapy, or diseases of the immune system.
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