Neutrophils are the most abundant type of white blood cell in the body and are responsible for helping your body fight infection. When a germ is initially detected by the body, neutrophils are the defence system which go out and attack the germ before any of your other white blood cells. When neutrophils are low you can be more vulnerable to illness and infection.
What might a low result mean?
A low level of neutrophils in the blood is called neutropenia, and is generally a temporary finding after an infection when your neutrophils can be depleted. Low neutrophils can also be caused by taking certain medications which may directly or indirectly lower neutrophil levels. Examples of these medications include chemotherapies, immunosuppressants and some antibiotics.
Low levels of neutrophils can also be found with conditions which suppress the bone marrow, such as aplastic anaemia, and in conditions such as AIDS, in which the HIV virus attacks the immune system.
What might a high result mean?
An elevated level of neutrophils in the blood is called neutrophilia, and generally indicates that you have a infection. When under attack from bacteria or a virus your immune system produces more neutrophils to send out into the blood to destroy the invader.
Elevated levels of neutrophils can also be found in people who exercise intensively, who have high stress levels or who take steroid medication such as prednisolone or cortisone.