A low white blood cell count, or leukopenia, is a decrease in disease-fighting cells (leukocytes) circulating in your blood.

The threshold for a low white blood cell count varies from one medical practice to another. Some healthy people have white cell counts that are lower than what's considered normal. A count lower than 4,000 white blood cells per microliter of blood is generally considered a low white blood cell count. The threshold for a low white blood cell count in children varies with age and sex.

Jan. 03, 2013