Chemotherapy and Low White Blood Cell Counts

Chemotherapy kills fast dividing cancer cells. It also ends up killing some fast dividing normal cells in the body, like those in the bone marrow that maintain the supply of white blood cells, or WBC, in your circulation. WBC counts fall temporarily with many different agents used as chemotherapy to treat cancer. With blood cancers such as leukemia and lymphoma, the cancers themselves can also cause WBC counts to fall when cancerous cells replace the healthy blood-forming cells in the bone marrow.

Often when chemotherapy affects WBC levels, it also causes a decrease in other cells and cell products in the blood, such as red blood cells and platelets.

Blood flowing in veins red and white blood cells
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When Do WBC Counts Fall?

The decrease in white blood cell levels starts a few days after chemotherapy is administered, reaching the lowest levels in the second or third week after chemotherapy. As the bone marrow cells recover from the effects of chemotherapy, the WBC counts start rising again. Before each cycle of chemotherapy, blood counts are verified to ensure that they have returned to the normal range.

Are Low WBC Counts Dangerous?

White blood cells are responsible for protecting the body from infections. When WBC counts are low, the risk of infections increases. When counts are low enough, the body cannot easily control these infections.

However, low counts do not always lead to infections. Nearly all people on chemotherapy have low counts during chemotherapy. But only some people develop serious infections related to low WBC counts.

How Do Healthcare Providers Check for Low WBC Counts?

At regular intervals during chemotherapy, blood tests to check cell counts are required. These tests are called CBCs or ‘Hemograms.’ White blood cell counts are reported as total leukocyte counts, or TLCs. TLCs count the different types of white blood cells. A more specific count is the absolute neutrophil count (ANC). Neutrophils are one type of WBC, and levels of neutrophils are very predictive for how well the body will be able to control bacterial infections. When the ANC is below a particular value, healthcare providers may delay further chemotherapy and start medications to prevent or treat infections.

Signs of Infection During Chemotherapy

The most telltale sign of infection is a fever. When fever occurs in the presence of low neutrophil counts (ANC), it is called febrile neutropenia. Other signs of infection include:

  • Cough and expectoration
  • Loose stools
  • Boils or abscesses
  • Severe sore mouth and swallowing problems

Contact your healthcare provider immediately if you have any of the above signs or symptoms during chemotherapy.

Preventing Infections

A few simple steps can reduce your chances of infection:

  • Avoid extremes of temperature and stresses that can lower immunity
  • Make sure that food is freshly cooked to avoid the risk of food-borne illness
  • Remember to wash hands before meals
  • Avoid contact with people who have any infections
  • Avoid crowded places with poor ventilation

Antibiotics are not routinely used when counts are low and there are no signs of infection. However, each person’s situation may be different. Your healthcare provider decides on the need for antibiotics based on specific signs and risk factors, as well as information that’s very specific to your individual medical history and clinical scenario.

How Low WBC Counts Are Managed

In the majority of cases, low counts are temporary. Counts start rising soon and reach normal levels without causing infections, and further chemotherapy may be continued.

When the blood counts are too low or there is a hint of infection in the body, healthcare providers may:

  • Delay further chemotherapy until the counts are normal.
  • Start drugs that increase white blood cell counts. These are called colony-stimulating factors, or CSFs. G-CSF and GM-CSF are the two types of CSF available.
  • Start treatment with antibiotics if there is any sign of infections in the body.

Not all people who develop low WBC counts are good candidates for drugs that increase these counts.


Sometimes stimulating the body to produce more new blood cells can be helpful when one or more of your blood cell counts is low or your counts are expected to become very low. For instance, sometimes the bone marrow is stimulated in advance, as a preventive measure, when counts are expected to fall due to a planned cancer therapy.

Experts have developed multiple sets of guidelines about when bone marrow stimulating agents should and should not be used. Much of the focus is on making sure the risks and benefits of bone marrow stimulation are balanced in a patient’s favor, and there are many, many different clinical factors to consider.

Studies are underway to try to find out the best way to tell which patients might benefit from growth factors that boost blood cell production. Researchers are also interested in determining the best way to combine growth factors with each other—and with other agents that include chemotherapy and hormone therapy.

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5 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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