Understanding Low White Blood Cell Counts

How a low white blood cell count affects health and how the doctor might treat it

By , Caring.com senior editor
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White blood cells are the body's best defensive weapons in the fight against germs and disease, so when white blood cell counts drop as a result of chemotherapy, radiation treatment, or certain types of cancer, it puts the patient in a vulnerable position. Without adequate protection from these disease-fighting cells, viruses and bacteria suddenly become much more serious threats.

Why does chemotherapy make white blood cell counts drop?

Think of chemotherapy as a smart bomb: It only targets certain types of cells, particularly those that grow and divide rapidly. That means it targets tumor cells, but it also means that white blood cells, which are produced in the bone marrow and have a rapid turnover rate, can be damaged as well. White blood cell counts, sometimes called leukocyte counts, drop with most chemo drugs. Neutrophils, which are a specific type of white blood cell, are the most potent disease fighters. The doctor may refer to a low white blood cell count as neutropenia, since a shortage of neutrophils is often what the doctor is most concerned about.

What are the risks of having a low white blood cell count?

White blood cells, or leukocytes, help fight bacteria and viruses. They're like the armed guards at the gates of the body, driving back the invaders. When there are too few white blood cells, a patient's immune system is compromised, putting him or her at increased risk of all types of infection: bacterial, viral, and fungal.