By Mayo Clinic Staff

Neutropenia (noo-troe-PEE-nee-uh) is an abnormally low level of neutrophils. Neutrophils are a common type of white blood cell important to fighting off infections — particularly those caused by bacteria.

For adults, counts of less than 1,500 neutrophils per microliter of blood are considered to be neutropenia. For children, the cell count indicating neutropenia varies with age.

Some people have lower-than-average neutrophil counts, but not an increased risk of infection. In these situations their neutropenia isn't a concern. Neutrophil counts less than 1,000 neutrophils per microliter — and especially counts of less than 500 neutrophils per microliter — are always considered to be neutropenia, where even the normal bacteria from your mouth and digestive tract can cause serious infections.

Jan. 20, 2016