Neutrophils are a type of leukocyte or white blood cell. They are responsible for the body's defense and increase when infection or inflammation is occurring. Segmented neutrophils, are mature neutrophils that are found in the highest number in the blood. They help to surround infected or injured cells and eliminate them.

The normal reference value of circulating segmented neutrophils in the blood may vary depending on the laboratory, however, in general, people will have 1600 to 8000 segmented neutrophils per mm³ of blood. Therefore, when neutrophils are high, it may be a sign of a bacterial or fungal infection.

In addition to the number of segmented neutrophils, a complete blood count may also indicate eosinophil, basophil and rod neutrophils levels. These are neutrophils that are also produced in the presence of infection or inflammation.

Normal levels

Normal levels of neutrophils will usually be between 1600 and 8000 neutrophils per mm³ of blood which corresponds to about 35 to 66% of the blood.

Read more about segmented neutrophils and how they work in the body.

What causes high neutrophils?

An increase in the number of neutrophils, also known as neutrophilia, can happen with several conditions such as:

Infections
Inflammatory disorders
Diabetes
Uremia
Eclampsia in pregnancy
Liver necrosis
Chronic myeloid leukemia
Post-splenectomy polycythemia
Hemolytic anemia
Myeloproliferative syndromes
Bleeding
Burn
Electric shock
Cancer

Neutrophilia can also occur due to physiological conditions in newborns, or during childbirth. Neutrophils can also increase after episodes of repeated vomiting, fear, stress, use of adrenaline medications, anxiety and after excessive physical activity. Therefore, if neutrophil counts are high, the doctor may order other diagnostic tests to correctly identify the cause and initiate appropriate treatment.

2. Low neutrophils

A decrease in the number of neutrophils, also called neutropenia, can occur due to:

Aplastic, megaloblastic or iron deficiency anemia
Leukemia
Hypothyroidism
Use of medications
Autoimmune diseases, such as Systemic Lupus Erythematosus
Myelofibrosis
Cirrhosis

Neonatal neutropenia may occur in cases of severe viral or bacterial infection after birth. Children with Down syndrome also tend to have low neutrophils without any health problems.

Patients with neutropenia may be ordered further blood work to investigate why levels are low. The doctor may also order a bone marrow test to assess the production of neutrophil precursor cells in the bone marrow.