What is neutropenia?

Neutropenia, sometimes called febrile neutropenia, is a form of fever combined with low white blood cell counts. Specifically, neutrophils are infection-fighting white blood cells that decrease in number in neutropenia.

Typically, people at risk for neutropenia are those whose immune systems have been weakened by cancer treatments such as chemotherapy and hematopoietic stem cell transplants. Others at risk are those who are immunosuppressed due to organ transplantation or treatment for autoimmune diseases.


neutrophils Because they are a type of immune cell that responds to bacterial and fungal infections, they play an important role in the body. If the level of neutrophils in the blood is low, the body’s ability to fight infection is limited.

In febrile neutropenia, a person has a low neutrophil count and a fever at the same time. Definitions used in neutropenia include:

  • Neutropenia or low neutrophil levels determined by blood tests and defined as an absolute neutrophil count (ANC) below 500 cells per microliter (cells/µL) or an expected level to be below 500 cells/µL for 48 hours.
  • A fever is defined as a temperature consistently above 100.4 degrees Fahrenheit for at least an hour, or a single temperature reading above 101 degrees.

In people with weakened immune systems, neutropenia can be a sign of infection. It is considered a medical emergency requiring prompt evaluation and treatment.

Signs and symptoms of neutropenia

In addition to fever, you may also notice symptoms such as chills, cough, sore throat or fatigue. However, when the immune system is weakened, normal signs of infection may not always be present. Therefore, neutropenia may be one of the first signs of infection in your body.

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Cause and Risk

The first step in the evaluation is to determine what may be causing the neutropenia, i.e. whether it is caused by an infection or another cause, such as chemotherapy, drugs to treat cancer. Chemotherapy can reduce your immune system’s ability to fight infections and make those infections worse.

In many cases, chemotherapy and stem cell therapy for cancer may be directly related to neutropenia. During chemotherapy, neutrophil levels naturally reach low levels around 7 to 10 days after treatment.

Certain cancer treatments, such as stem cell transplantation and chimeric antigen receptor T-cell (CAR-T) therapy, may also play a role in the development of neutropenia.


Neutropenia occurs in 5 to 30 percent of people who receive chemotherapy for solid tumors, usually during the first treatment cycle. Neutropenia persisted longer in people who received chemotherapy for leukemia or who were preparing for a stem cell transplant, and more than 80% of them developed neutropenia.

Diagnosis and treatment of neutropenic fever

Neutropenia is diagnosed when a low neutrophil count is accompanied by fever. Neutrophil counts are determined as part of a differential complete blood count (CBC), a common blood test.

Treatment of neutropenia focuses on identifying and evaluating underlying causes, such as chemotherapy and infection. If your neutropenia is severe enough, you may be treated with antibiotics that have broad coverage against a variety of bacteria.

Blood tests to evaluate bacteria and viruses can be used to help guide antibiotic treatment. It’s worth noting, however, that blood tests are limited and can only identify the culprit in about 50 percent of people with neutropenia.

Most of the bacteria that cause neutropenia are actually normal bacteria that live in the body and gut. When the immune system is weakened, bacteria from the gut can cross the mucosal surfaces of the gastrointestinal tract and enter the bloodstream, causing widespread infection.

Other common sources of infection are catheters and central lines used to deliver chemotherapy drugs into veins. If these centerlines and catheters are left in the body for a long time, or if they are not cleaned properly, bacteria that live on the skin can enter the body.

In some cases, bacteria from the skin can enter these ducts and enter the entire bloodstream and cause widespread infection. Fortunately, antibiotic treatment can help the body fight these infections even if the immune system is weakened.

Treatments of choice designed to support immune system function are also used. A treatment called granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) is used to strengthen the immune system. Neupogen and Neulasta (filgrastim) are G-CSF-based drugs.

These colony-stimulating factor treatments promote the production of white blood cells in the bone marrow and work to increase circulating levels of neutrophils and macrophages (another type of white blood cell).

In some cases, your healthcare provider may prescribe these colony-stimulating factors along with chemotherapy to prevent neutropenia (prophylactic treatment).


Neutropenic fever is persistent or severe fever in patients with low white blood cell counts. Cancer treatments such as chemotherapy and hematopoietic stem cell transplantation (HSCT) are the most common causes of neutropenic fever. A bacterial infection may or may not be detected.

Treatment may include antibiotics. Drugs that stimulate leukogenesis, such as Neupogen and Neulasta, can be used.

VigorTip words

Neutropenic fever can occur at any time during cancer treatment and does not always indicate that the cancer is progressing or getting worse. Finding neutropenia early and starting treatment can go a long way.

Frequently Asked Questions

  • What causes neutropenia?

    Neutropenia can have a variety of potential causes. Neutropenia is common in people undergoing cancer treatment, such as chemotherapy. Some of these treatments are known to cause neutropenia. Additionally, these treatments may increase the risk of developing an infection that can lead to neutropenia.

  • What is the most common source of infection that causes neutropenia?

    The most common bacteria that cause neutropenia are those that occur naturally in places like the gut and skin. While these bacteria usually don’t cause problems, when the immune system is weakened, the bacteria can lead to infections.

  • Is neutropenia an emergency?

    Neutropenic fever is a medical emergency that requires prompt evaluation and treatment. Because many people with febrile neutropenia are being treated for cancer, it is important to seek emergency medical care right away if you have neutropenia.

  • How to prevent neutropenia?

    Prediction and prevention of neutropenia can be challenging, but hygiene practices, such as thorough hand washing, avoiding crowded places, and limiting contact with children, are known to reduce the risk of neutropenia.

    In some cases, your healthcare provider may recommend that you take regular antibiotic medication to prevent neutropenia. Treatments called colony-stimulating factors, which aim to increase immune cell counts, may also help prevent neutropenia.