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What to Know About Neutrophils

Medically Reviewed by Dan Brennan, MD on June 12, 2021

Neutrophils are a type of white blood cell. They make up the biggest number of all kinds of white blood cells. They kill and digest bacteria and fungi to help your body fight infections and heal wounds. 

Neutrophils in White Blood Cells

White blood cells make up about 1% of your body's total blood cells and are an important part of your immune system. Neutrophils are the cells that respond first to any type of infection or wound. These make up 50% to 75% of your white blood cells. Neutrophils are made in your bone marrow. They live less than a day, so your bone marrow constantly makes new ones.

Testing for Neutrophils

If your doctor thinks your neutrophil count may be low or high, they may order an absolute neutrophil count (ANC) test. This 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 your blood. The differential tells how many of each type of white blood cell is in your blood. The ANC tells how many neutrophils are in your blood.  

Normal neutrophil counts depend on different factors such as age — but generally, a low neutrophil level is less than 45% of your total white blood cells or 1,5000 neutrophils per microliter. A normal neutrophil level is between 1,500 and 8,000 neutrophils per microliter. A high neutrophil level is over 8,000 neutrophils per microliter. 

What Can Cause a High Neutrophil Count?

A high neutrophil count is called neutrophilia or neutrophilic leukocytosis. It can be caused by a lot of different conditions, including: 

Infection. This is the most common cause of a high neutrophil count. Most bacterial infections cause a high neutrophil count but not all of them do. Viral infections don't generally cause neutrophilia but they may in the early stage of infection. Some fungal and parasitic infections can cause neutrophilia as well.

Inflammation. Any condition that causes inflammation in your body can increase your neutrophil count. Examples of this include:

  • Rheumatoid arthritis and gout, which are types of arthritis
  • Ulcerative colitis, which is irritation and ulcers in your large intestine
  • Tissue damage from burns, surgery, or trauma
  • Loss of blood
  • Sickle cell crisis, which is a type of red blood cell disorder
  • Acute kidney failure
  • Diabetic ketoacidosis, a serious complication of diabetes when acids build up in your blood
  • Cushing's syndrome, which is when your body has too much cortisol
  • Pre-eclampsia and eclampsia, which are complications of pregnancy that can cause organ damage
  • Heart attack
  • Acute hypoxia, which is a lack of oxygen

Medicines. Some medicines can cause neutrophilia, such as:

  • Lithium
  • Heparin
  • Antiepileptic drugs
  • Minocycline
  • Clozapine 
  • Corticosteroids 

Some types of cancer. Cancers that can cause neutrophilia include:

How Is a High Neutrophil Count Treated?

The treatment for neutrophilia involves treating the underlying cause. A high neutrophil count isn't a problem on its own. Your doctor will do tests to find out what is causing you to have neutrophilia and treat that. 

What Can Cause a Low Neutrophil Count?

A low neutrophil count is called neutropenia. Since neutrophils are cells that are part of your immune response to fight infections, neutropenia can make you more likely to get an infection. If you have severe neutropenia, even normal bacteria on your body can cause serious infections. There are many different conditions and some medications that can cause neutropenia. 

Cancers and cancer treatment. Cancers that affect your bone marrow, such as lymphoma, leukemia, and myeloma, can cause neutropenia. Chemotherapy and radiation prevent your body from producing neutrophils, so neutropenia is an expected side effect of this cancer treatment. 

Infections. Some types of infections can cause neutropenia, such as:

Sepsis, which is an extreme response your body can have to an infection, can also lead to neutropenia.‌

Medicines. Many medicines have been linked with neutropenia. This is called drug-induced neutropenia and usually happens within 6 months of starting the medicine. Once you quit taking the medicine, the neutropenia usually clears up within one week.

Some of these medicines include:

Bone marrow disorders. Conditions that affect your bone marrow such as aplastic anemia, myelodysplastic syndrome, and myelofibrosis can cause neutropenia. 

How Is a Low Neutrophil Count Treated?

The treatment of neutropenia will depend on its cause and severity. It's important to treat any source of infection in people with neutropenia. If you have neutropenia and fever, your doctor may treat you with antibiotics even if no source of infection can be found. If your doctor thinks your medicine may be causing neutropenia, they may switch your prescription to a different medicine.

You may be given medicine that will stimulate your body to make more white blood cells. If you have an autoimmune disorder that is causing your neutropenia, your doctor may prescribe corticosteroids. If your neutropenia is caused by an underlying disorder, treatment of it may clear up the neutropenia. 

WebMD Medical Reference

Sources

SOURCES:

American Cancer Society: "Chronic Myeloid Leukemia (CML)."

American Society of Hematology: "Blood Basics."

Centers for Disease Control and Prevention: "What is sepsis?"

Cleveland Clinic: "Ulcerative Colitis."

GP: "Causes of neutrophilia and treatment."

Lab Tests Online: "Complete Blood Count (CBC)."

Mayo Clinic: "Cushing syndrome," "Neutropenia," "Preeclampsia," "Sickle cell anemia."

The University of Texas MD Anderson Cancer Center: "Cancer treatment side effect: Neutropenia."

Medscape: "What are the causes of neutrophilia in leukocytosis?" "Which medications cause neutropenia?"

Merck Manual: "Neutrophilic Leukocytosis," "Neutropenia."

Self Decode: "Neutrophils: Functions & Related Diseases."

St. Jude Children's Research Center: "Juvenile Myelomonocytic Leukemia."

Stanford Children's Health: "What Are White Blood Cells?"

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