Definition

By Mayo Clinic Staff

A low white blood cell count is a lower number of the cells in the blood that fight illness.

What's thought of as low in a white blood cell count varies from one lab to another. This is because labs set their own reference ranges based on the people they serve. Most often, a count lower than 3,500 white blood cells per microliter of blood is thought to be low for adults. For children, an expected count depends on the age.

Some people can have white blood cell counts that are lower without being ill. For instance, Black people tend to have lower counts than white people do.

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Feb. 19, 2026

See also

  1. Pediatric white blood cell disorders