White Blood Cell Count (WBC)

About The Test

White blood cells (WBCs), also called leukocytes, are an important part of the immune system. Made in the bone marrow, WBCs help to defend the body against infections and disease. There are five types of white blood cells, each supporting the immune system in a different way.

A white blood cell count is a test that measures the number of leukocytes in the blood. This test is most often conducted at the same time as other measurements in a complete blood count (CBC), a common test used to diagnose and monitor a wide variety of health conditions.

A WBC count can help diagnose infections, inflammation, and other health conditions that affect white blood cells. If the results of a WBC count are outside of the healthy range, additional tests are performed to diagnose the cause.

A related test, called a white blood cell differential, measures the percentage of each type of white blood cell in the blood and may also be included with a complete blood count.