What Is Granulocytopenia?

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Granulocytes are a family of specialized white blood cells produced in the bone marrow that include neutrophils, basophils, and eosinophils. Low granulocyte levels, also known as granulocytopenia, occur when the levels of one or all of these cell lines fall below normal limits.

Granulocytopenia puts you at risk for bacterial, viral, or fungal infection and should be treated promptly.

An illustration with treatment of granulocytopenia

Illustration by Jessica Olah for Verywell Health

When granulocyte levels are extremely low, you have a more severe disorder known as agranulocytosis. Agranulocytosis is considered to be an absence of granulocytes and occurs when the body fails to make granulocytes.

This article reviews the functions of granulocytes and what happens if levels become too low, causing granulocytopenia.

Functions and Types of Granulocytes

The granulocytes are a subset of white blood cells that work to control and coordinate the immune system.

The granulocytes are named after collections of granules contained inside the cells that help them perform specific functions. The granules inside the cells give the cells a dark coloration that makes them distinct from other cells such as red blood cells or macrophages, another type of white blood cell.

Granulocytes found in the blood include:

  • Basophils: These white blood cells trigger a response to allergies and inflammation. They play a critical role in recruiting other immune cells to the source of an allergen in the body. 
  • Eosinophils: Responsible for managing chronic inflammation and parasitic infections, these cells can be involved in the body's response to allergies, cancer, and parasitic infections.
  • Neutrophils: These cells move to a site of infection and eliminate bacteria, viruses, fungi, and parasites. Neutrophils are the most abundant cells at the site of an infection and make up the majority of your granulocyte level. Neutrophil levels can be used to evaluate granulocytopenia. 

What Causes Granulocytopenia?

The granulocyte levels are evaluated using blood work and laboratory tests such as a complete blood count.

A complete blood count (CBC) is a laboratory test that can count the specific populations of white blood cells circulating in the bloodstream. If the granulocyte populations are low then you may be diagnosed with granulocytopenia. This may be an indicator of one or more of the following disorders:

  • Immunocompromised state 
  • Autoimmune disorders (systemic lupus erythematosus)
  • Bone marrow failure
  • Cancer neoplasms
  • Genetic disorders 

Certain medications can also cause granulocytopenia. Myelosuppressive chemotherapy, which makes the bone marrow less able to produce blood cells, can cause the disorder in some people. HIV medications can interfere with hematopoiesis, the process by which blood cells are formed, and that can lead to low granulocyte levels. Other drugs that can contribute to granulocytopenia include immunosuppressants, antipsychotics, and anti-epileptics.

Treatments for Low Granulocytes

Specific medications aimed at increasing the production of white blood cells are used to treat low granulocyte levels. This includes:

  • Neupogen (filgrastim): Commonly known as granulocyte colony-stimulating factor (G-CSF), this growth factor helps increase the production of granulocytes by the bone marrow, which can increase the population of granulocytes in the blood and correct granulocytopenia.  
  • Antibiotics are often used as treatments for granulocytopenia due to the increased risk of infection. Antibiotics can be used as prophylaxis before an infection develops or as a treatment for current infection. Appropriate selection and optimization of antibiotic therapy is necessary to target the most likely infections you may be at risk for.
  • Bone marrow transplant: This procedure may be necessary if drugs are unable to correct the granulocyte levels. A bone marrow transplant involves implanting bone marrow from a donor to help restart the production of granulocytes.


Granulocytopenia, low levels of certain white blood cells, can compromise the body's ability to fight infections. The disorder may be a sign of an underlying health condition or a side effect of certain prescription drugs. Medication and, in some instances, a bone marrow transplant may be necessary to treat or manage granulocytopenia.

A Word From Verywell

Low granulocyte levels are a challenging diagnosis to navigate. Since granulocytopenia is often the result of other disorders, treatment may be complex. Your healthcare provider must balance the low white blood cell count while protecting you from underlying health problems. It's completely normal to feel like the terminology and treatments sound strange and unfamiliar. Working with your healthcare provider will help you get through the process so you can enjoy better health.

Frequently Asked Questions

  • What is the difference between agranulocytosis and granulocytopenia?

    Agranulocytosis is a more severe form of granulocytopenia where there are extremely low, or absent, levels of granulocytes in the blood. Agranulocytosis is considered a form of bone marrow failure and may require more advanced treatments such as bone marrow transplants. 

  • What are the common causes of granulocytopenia?

    The most common causes of granulocytopenia are chemotherapy treatments for cancer, adverse drug reactions, autoimmune disorders that affect the bone marrow, and bone marrow failure.

  • What is leukopenic granulocytopenia?

    A leukopenia is a type of granulocytopenia characterized by low levels of white blood cells known as lymphocytes in the bloodstream. Both lymphocyte and granulocyte cell levels are low in leukopenic granulocytopenia and may indicate a more severe disease affecting the bone marrow production of all white blood cells.

  • Which medications cause granulocytopenia?

    There are many medications that have the potential to cause granulocytopenia, including chemotherapy treatments, immunosuppressants, antipsychotics, HIV antivirals, anti-epileptics, anti-thyroid, certain antibiotics, antiarrhythmics, and others).

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Kevin James Cyr
Kevin is a physician-in-training at Stanford University School of Medicine with a focus in cardiovascular disease and bioengineering. His publications have earned international awards, and his work has been featured in major media outlets such as NBC News.