Neutrophils are a type of white blood cell that act as the immune systems first line of defense. They are the most common type of white blood cell and make up anywhere from 50% to 80% of all white blood cells in the body. Neutrophils are made in the bone marrow and migrate through the circulation system in the blood and tissues. They kill and digest bacteria and fungi to help the body fight infections and heal wounds.

An absolute neutrophil count (ANC) is a test that measures the number of neutrophils in the blood. A normal ANC range is between 1,500 and 7,700 neutrophils per microliter of blood. A low absolute neutrophil count is referred to as neutropenia, which occurs when the ANC is less than 2,500 cells/mcL. A lower than normal number of neutrophils (lower than 500) is called severe neutropenia. The lower a persons ANC is, the higher the risk of getting an infection. A high absolute neutrophil count means the body is under stress, and it can be caused by infection, inflammation, stress, and vigorous exercise.

If a doctor thinks a patients neutrophil count may be low or high, they may order an ANC test, which is usually done as part of a complete blood count (CBC) with differential. The CBC tells how many of each type of blood cell is in the blood, while the differential tells how many of each type of white blood cell is in the blood. The ANC tells how many neutrophils are in the blood.