What Is Granulocytosis and When Does It Occur?

It can be a sign of disease

Granulocytosis is an overabundance of granulocytes in the blood. Granulocytes include some types of white blood cells that play many different roles in the immune system.

Blood smear from chronic myeloid leukemia shows granulocytosis and immature blasts


Your granulocytes can temporarily increase when you have an infection, and they can also be persistently elevated due to inflammatory or autoimmune conditions. Some types of cancer can make granulocyte levels change—causing either granulocytosis or low levels of granulocytes at different stages of the disease. 

What Is a Granulocyte?

A granulocyte is a type of white blood cell that has a granular appearance when viewed under a microscope. White blood cells, including granulocytes, develop in the bone marrow. 

Types of Granulocytes

Granulocytes are produced in the bone marrow and they all come from the same precursor. They differentiate as they mature and prepare to fight disease. They include:

  • Neutrophils: The most common type of white blood cell, neutrophils help with tissue healing and fighting infections, especially bacterial infections.
  • Eosinophils: Eosinophils are associated with allergies, parasitic infections, and cancer.
  • BasophilsBasophils are granulocytes that are involved with inflammation. They can release histamine, which causes a variety of responses, and heparin, which prevents blood from clotting.
  • Mast cells: Mast cells recognize harmful infectious organisms and they aid in releasing inflammatory chemicals to help augment the immune response.


Granulocytes normally increase when you have an infection. They help your body fight infections, and they will go back to normal levels as the infection resolves. 

Some medical conditions can cause granulocytes to increase. In these situations, granulocytes can increase due to excessive and abnormal production, and this can cause symptoms such as swelling, pain, fatigue, and fever.

Causes of increased granulocytes include:

  • Inflammatory diseases such as vasculitis (inflammation of the blood vessels)
  • Bacterial infections, such as tuberculosis
  • Viral infections, such as Ebola
  • Sepsis (a severe reaction to a blood infection)
  • Autoimmune diseases, such as rheumatoid arthritis (which affects the joints and other areas of the body) or lupus (which can affect many systems within the body) 
  • Medication toxicity
  • Bone marrow disorders 
  • Cancer 

Granulocytes also increase in response to certain lifestyle conditions, including smoking and chronic sleep disruption.

In research studies, these lifestyle issues have been found to induce a low-grade granulocytosis, not the same degree of granulocytosis as an infection or medical illness. The effect of this low-grade granulocytosis isn’t fully understood, but it is believed to contribute to health complications.

Chronic Myeloid Leukemia 

Chronic myeloid leukemia (CML), also called chronic myelogenous leukemia or chronic granulocytic leukemia, is a type of blood cancer that occurs when the bone marrow makes too many white blood cells.

Chronic myeloid leukemia can cause granulocytosis. Depending on the phase of CML, immature white blood cells called blast cells may also be seen in the peripheral blood and be increased in the bone marrow.

Some people may not have noticeable symptoms of chronic myeloid leukemia, and the first sign could be granulocytosis noted on a blood test. 

This type of cancer can also cause low numbers of red blood cells and platelets, which are blood cells that also develop in the bone marrow. 

Signs and Symptoms 

Granulocytosis can cause symptoms related to the high white blood cell count, and it can also cause symptoms that are associated with the underlying causes. 

Examples include: 

  • Tuberculosis can cause a cough, hemoptysis (coughing blood), chest pain, and a fever.
  • Vasculitis can cause fever, as well as an area of swelling, redness, and tenderness. This may develop on the leg or other areas of the body. 
  • Bone marrow inhibition due to medications can cause bleeding, increased risk of infections, and symptoms of anemia, such as fatigue, pale skin, dizziness, headaches, and a rapid pulse. 


Granulocytosis is diagnosed with a blood test called a complete blood count (CBC). This test measures different types of blood cells, including white blood cells, red blood cells, platelets, and some other characteristics of blood, such as hemoglobin and hematocrit (the ratio of red blood cells to other blood elements by volume).

Granulocytes are measured as the number of cells per cubic millimeter and as a percentage of total leukocytes (white blood cells). Lymphocytes are a type of leukocyte, and granulocytes are a type of leukocyte. Standard values may vary from one lab to another, but the values below are widely accepted.

Normal granulocyte values
  Cells per cubic millimeter Percent of total leukocytes
Total lymphocyte count 1,000–4,000 20%–40%
Neutrophils 2,500–6,000 40%–60%
Eosinophils 50–300 1%–3%
Basophils 0–100 0%–1%
Mast cells not measured by standard tests

If you have granulocytosis, you may need further testing with a blood smear, imaging tests, or a biopsy (removing a sample of tissue for analysis in a lab), such as a bone marrow biopsy, to identify the cause.

With some conditions, including cancer and bone marrow disease, granulocytes can increase at times and decrease at other times. In fact, the change in number can signal different disease stages.

For example, granulocytes can be elevated during flare-ups of inflammatory disease. And some cancers may cause granulocytosis in early stages, with decreased granulocytes in later stages or as a result of treatment that affects the bone marrow. 


Granulocytosis is an increase in granulocytes in the blood. Granulocytes are a type of white blood cell that helps the body fight infections. Granulocytosis can be an increase in mature or immature granulocytes, and it can occur due to infections, inflammation, or cancer.

Sometimes granulocytosis resolves if the condition is temporary, like an infection. At times, granulocytosis is a sign of a serious medical illness and further tests, such as a biopsy, may be needed. 

A Word From Verywell 

Having granulocytosis can mean many different things. While many causes of granulocytosis resolve on their own, some causes require further testing, as well as treatment. For instance, you may need to have a biopsy or imaging tests.

If you need treatment, you will likely have repeat blood tests to see if your granulocytosis is resolving. Follow-up blood tests can help monitor treatment and follow the progression of your underlying condition.

Frequently Asked Questions

  • Is granulocytosis treatable?

    Yes, often granulocytosis can be treated. Generally, specific therapies that treat the cause are used. For example, chronic myeloid leukemia is treated with chemotherapy, and inflammatory disorders may be treated with interventions that suppress excessive immune system activity.

  • What is an immature granulocyte?

    An immature granulocyte is not fully developed into the mature version of the cell. It might be at a stage in which it is not differentiated and might not show signs of a specific type of mature granulocyte.

    Immature granulocytes are normally found in the bone marrow, and some medical conditions can cause them to enter the blood.

  • Can somebody have a low granulocyte count?

    Yes, one or more types of granulocytes can be low. This is a sign of health problems, such as bone marrow disorders, and it can also occur as a side effect of medications and treatments that interfere with the production of blood cells in the bone marrow.

9 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 Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.