What a High and Low Neutrophil Count Means (2024)

A high neutrophil count and a low neutrophil count can occur as a result of certain infections, diseases, autoimmune disorders, cancers, medications, or medical treatments. This type of white blood cell is part of the immune system's frontline defense, and having too many or too few can mean vastly different things.

A healthy adult has between 2,500 and 6,000 neutrophils per microliter (µL) of blood. There are several reasons why neutrophils may fall outside of this reference range of values:

• A count below 2,500 (neutropenia) can occur with chronic infections, autoimmune diseases, medication side effects, and congenital conditions you are born with.
• A count above 6,000 (neutrophilia) can occur with acute infections, injuries, inflammatory conditions, cancers, and medications like steroids.

This article explains what neutrophils are and their role in maintaining your health. It also discusses neutrophil blood testing, as well as the causes of neutropenia and neutrophilia

What Are Neutrophils?

Neutrophils are a type of white blood cell that makes up approximately 40% to 60% of all of your white blood cells (WBCs). Neutrophils are produced by bone marrow, but they can be found in the blood, tissues, and lymph nodes throughout the body.

Among their many functions, neutrophils protect you from infection. As part of your innate immune response, neutrophils are one of the first WBCs to arrive on the scene when you get a bacterial infection.

Neutrophils are classified as both granulocytes and phagocytes. By definition:

• Granulocytes contain granules that are released when the cell breaks open (degranulates). The granules have antimicrobial properties that can help control bacterial, fungal, and viral infections.
• Phagocytes engulf and ingest disease-causing microorganisms as part of the immune system's frontline attack. The process, known as phagocytosis, is the main way that the body deals with bacterial and fungal infections.

Neutrophils have a lifespan of less than 24 hours, but your body makes about 100 billion of these WBCs every day.

When You May Need a Neutrophil Count

An absolute neutrophil count (ANC) is part of a battery of tests known as a complete blood count (CBC). This may be done as part of a routine exam or to help your healthcare provider diagnose certain conditions.

The ANC is calculated by multiplying the total number of WBCs by the combined number of mature neutrophils (called "segs" or segmented cells) and immature neutrophils (called "bands").

If the ANC is higher or lower than the normal range of values—between 2,500 and 6,000—further evaluation will be needed to help determine the underlying cause.

High Neutrophil Levels

Neutrophil levels above 6,000 are considered high, a condition known as neutrophilia. This may be due to a number of mechanisms that increase the number of neutrophils in response to various diseases or circ*mstances.

Examples include:

• Reactive neutrophilia: This is an increase in neutrophils to help fight infections. It can also occur when the body is placed under stress by injury or a toxic substance. The increased production is aimed at neutralizing the threat.
• Proliferative neutrophilia: This is an increase in neutrophils caused by cancers that accelerate the production of WBCs from bone marrow.
• Neutrophilic demargination: This occurs when neutrophils detach from the organs where they usually reside (like the spleen, liver, bone marrow, and blood vessels) to freely circulate in the bloodstream. This can happen when the body is placed under stress, faced with an inflammatory disease, or exposed to drugs that trigger the stress hormone cortisol.
  

Conditions That May Cause Neutrophilia

Neutrophilia can be categorized as being either primary (caused by a congenital disorder or disease of the bone marrow specifically) or secondary (caused by infections, inflammation, stress, and other medical conditions).

Causes of primary neutrophilia include:

• Chronic myeloid leukemia (CML)
• Essential thrombocytosis (ET)
• Polycythemia vera (PV)
• Juvenile myelomonocytic leukemia (JMML)
• Chronic neutrophilic leukemia (CNL)

Causes of secondary neutrophilia include:

• Infections
• Inflammation
• Emotional or physical stress (including vigorous exercise)
• Autoimmune disorders, such as rheumatoid arthritis
• Inflammatory diseases like inflammatory bowel disease (IBD) and vasculitis
• Trauma and burns
• Smoking
• Medications such as corticosteroids and lithium
• Solid tumor cancers (including bone marrow metastasis)

Low Neutrophil Levels

Levels of neutrophils less than 2,500 are referred to as neutropenia.A level of less than 1,000 is the most serious and can increase the risk of infection.

Symptoms of neutropenia can vary but may includefever,chills, fatigue, sore throat, mouth sores, cough, shortness of breath, skin sores, painful urination, or diarrhea.

Several mechanisms can result in a low neutrophil count:

• Decreased or absent bone marrow production describes when the bone marrow slows down or ceases to produce white blood cells. This can happen when the bone marrow is injured during chemotherapy or a vitamin deficiency causes inadequate production.
• Bone marrow infiltration occurs when the bone marrow is "taken over" by cancer cells, or by scar tissue (fibrosis) in conditions such as myelofibrosis.
• Demand for more neutrophils may occur when more neutrophils are needed in specific situations, such as to fight an infection or in response to trauma. With serious infections, a low neutrophil count may result as the immune system is overwhelmed by the infection.
• Decreased survival of neutrophils can occur as a result of overwhelming infection. Neutrophils may also face destruction due to antibodies that attack the body itself, such as those produced in autoimmune conditions like lupus.
• Cyclic neutropenia is a rare condition that can be inherited or acquired causing fluctuations in WBC production.
  

Conditions That May Cause Neutropenia

Via the mechanisms above, a decreased neutrophil count could be due to:

• Chemotherapy
• Aplastic anemia
• Radiation exposure
• Vitamin B12 deficiencyand folic acid deficiency
• Systemic lupus erythematosus (lupus)
• Myelodysplasia (a group of bone marrow conditions)
• Drug reactions to penicillin, ibuprofen, and phenytoin
• Parasitic infections like Rocky Mountain spotted fever
• Bacterial infections like tuberculosis and typhoid fever
• Viral infections like HIV and cytomegalovirus (CMV)
• Sepsis
  

Prevention

There are times when neutrophilia or neutropenia cannot be avoided, such as with certain congenital disorders and chronic diseases. Even so, there are ways to better maintain neutrophil levels to fight infection and remain healthy:

• Be aware of signs of infection. Early diagnosis and treatment can limit the severity of neutropenia.
• Wash your hands. Take standard precautions to prevent getting transmittable infections. This includes avoiding sick people.
• Get recommended vaccines. This includes annual vaccination for flu and COVID-19.
• Maintain healthy nutrition. A healthy, balanced diet can help strengthen your immune system and avoid nutritional deficiencies that contribute to neutropenia.

Summary

Neutrophils are a type of white blood cell (WBC) that play a key role in fighting off infection. Your level of neutrophils in the blood can change, depending on a number of factors, including infection, stress, chemotherapy treatment, or nutritional deficiencies.

In some cases, your neutrophil levels will be high. This condition is called neutrophilia. In cases of neutropenia, the level may be low—even dangerously low. Your healthcare provider can begin with blood tests and move forward in diagnosing the cause of any neutrophil level changes.