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High White Blood Cell Count

(Leukocytosis)

By

Mary Territo

, MD, David Geffen School of Medicine at UCLA

Last full review/revision Aug 2021| Content last modified Aug 2021
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White blood cells (leukocytes) are an important part of the body’s defense against infectious organisms and foreign substances (the immune system The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more ). The number of white blood cells (white cell count) is normally less than 11,000 cells per microliter of blood (11 × 109 per liter).

The most common cause of an increase in the white blood cell count is

  • The normal response of the body to an infection

Other causes include

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Test your knowledge

Anemia of Chronic Disease
Anemia is often caused by chronic disease, defined as any disease lasting 3 or more months. Autoimmune disorders, in which the body attacks its own tissues, are a common cause of this type of anemia. Which of the following autoimmune disorders most often causes anemia?
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