What Are Neutrophils?

Woman getting a blood test

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Neutrophils are a type of white blood cell. White blood cells help your body fight infections caused by pathogens, which are organisms like bacteria, viruses, fungi, and parasites that can cause diseases. Among the four types of white blood cells, neutrophils are the most common, making up 50-70% of the total amount of white blood cells.

Neutrophil count, which is the number of neutrophils circulating in your blood, can give you and your healthcare provider insight into the health of your immune system. Neutrophil count needs to remain in a specific range for your body to remain healthy. In the case of infection or certain health conditions, the count can become too high or too low.

What Do Neutrophils Do?

Neutrophils are a type of white blood cell. They provide the first line of defense against infection.

When antigens—foreign substances like bacteria and viruses that trigger an immune response—enter the body, neutrophils are one of the first cells to respond. Neutrophils first attack antigens by ingesting them, and then break down and destroy them.

Like the majority of white blood cells, neutrophils are made inside the bone’s soft tissue called the bone marrow. In the bone marrow, neutrophils are programmed to fight off different antigens. As neutrophils mature, they then migrate from the marrow into different body tissues and circulate in the blood. They remain in the blood for about 24 hours.

How Are Neutrophils Measured?

Adults and children should have a certain range of neutrophils in their blood, known as their neutrophil count.

To measure the number of neutrophils in your blood, a healthcare provider will usually draw blood from a vein in your arm and send the blood sample to a lab for analysis. The neutrophil count is typically ordered as a part of a complete blood count (CBC). The CBC is a test that determines the count of each type of blood cell.

Within the CBC, the absolute neutrophil count tells how many neutrophils are in your blood. Absolute neutrophil count has specific ranges for people of different ages. Children usually have a higher count than adults. For a healthy adult, the normal neutrophil count is 2,500-7,000 neutrophils per microliter of blood. 

Counts below or above that normal range can start to fall into categories of concern:

Condition Name Feature Neutrophil Count (neutrophils/microliter)
Severe Neutropenia A very low neutrophil count Below 500
Neutropenia A low neutrophil count Below 1,000
Neutrophilia A high neutrophil count Above 7,700 

What Does a Low Neutrophil Count Mean?

A low amount of neutrophils in the blood is called neutropenia. This can indicate you may be immunodeficient (your immune system cannot adequately fight infections), immunosuppressed (part of your immune system's ability to fight infection is blocked and reduced), or immunocompromised (you have a weakened immune system).

Neutropenia can occur in several conditions, including:

  • Bone marrow disorders and failure (when the bone marrow—the soft center of the bone that produces cells—can no longer make enough healthy cells for the body’s needs)
  • Cancers that directly affect the bone marrow, such as leukemia, lymphoma, and multiple myeloma
  • Infections
  • Autoimmune diseases, such as lupus and rheumatoid arthritis
  • High blood sugar

A low neutrophil count can also be a side effect of some medications, including penicillin, cephalosporins (antibiotics that treat skin infections, meningitis, and other bacterial infections), and drugs containing heavy metals.

Cancer treatments like chemotherapy and radiation therapy may also reduce the neutrophil count, causing it to drop below normal levels.

What Does a High Neutrophil Count Mean?

A high amount of neutrophils in the blood is called neutrophilia. Neutrophilia is typically a sign that your body is fighting an antigen and can suggest an active infection, but the high count can also occur because of:

  • Acute or chronic inflammation
  • Cancer
  • Burns or other types of tissue damage
  • Medication side effects or response
  • Myositis (conditions that cause muscle inflammation)

How Are Abnormal Neutrophil Counts Treated?

Treatment of a high or low neutrophil count depends on the underlying cause. A healthcare provider may order more tests to determine the root cause. Treatment may also depend on how high or low the count is.

Treatment for Low Neutrophils 

Neutropenia treatment mainly depends on the severity, or how low the count is.

The lower the count is, the greater your risk of getting an infection. Your healthcare provider may prescribe an antibiotic if you have a low neutrophil count and are having repeated bacterial infections.

If a medication is causing a low neutrophil count, a healthcare provider may choose to stop your medication or prescribe a new drug.

Some medications work to help your body make more neutrophils. In severe cases, your healthcare provider may prescribe such a drug that increases the neutrophil count as well as the function of the neutrophils.

Your healthcare provider may also order more tests to look for any underlying condition that may be causing the low neutrophil count. In that case, they would then be able to provide specific treatment related to the cause.

Treatment for High Neutrophils 

Neutrophilia treatment is largely dependent on treating the underlying cause of the high neutrophil count. A healthcare provider may do several tests to find the cause of the high neutrophil count so they can then treat the condition.

Some medications may also cause a high neutrophil count. In this case, you may be instructed to stop certain medications or be prescribed an alternative drug.

What to Ask Your Healthcare Provider

A CBC is commonly used as part of a routine checkup. A healthcare provider might also order a CBC if they suspect you have some sort of disorder and want to see if your blood levels reveal anything. If you’ve already been diagnosed with a disorder, a healthcare provider might order a CBC to monitor the condition.

If your doctor orders a CBC to check for neutrophil levels or the test shows reports of an abnormal neutrophil count, these questions may be beneficial to ask:

  • Why is the test being ordered?
  • Do I need to do anything to prepare for the blood test?
  • What other test(s) should I expect based on the results?
  • What happens if I get an abnormal result?
  • Could any of my medications be causing an abnormal count?
  • Are there any lifestyle changes I can make to help improve my blood count?

A Quick Review 

Neutrophils are the most common type of white blood cells and are among the first line of defense against pathogens. Your bone marrow is continuously making neutrophils to help you fight infection. Your neutrophil count can become too high or low based on several conditions.

A healthcare provider can determine your neutrophil count through a CBC. If your count is outside of the normal range, talk to a healthcare provider about finding the cause of abnormal levels so that you can start any necessary treatment or medication changes.

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