WBCs, also calledleukocytes, are immune system cells that fight pathogens in your body.
A high white blood cell count is calledleukocytosis.
A lowwhite blood cellcount is calledleukopenia.
Illustration by Jessica Olah for Verywell Health
High and Low White Blood Cell Counts
A normal white blood cell count varies by age.
Most of the time, though, leukocytosis indicates there is an infection in your body.
When this happens, your immune system releases cells to fight it off and heal your body.
This causes the number of white blood cells in your body to increase.
When cancer occurs in the bone marrow, it can cause reduced production of white blood cells.
In many cases, a low white blood cell count resulting from cancer treatments is temporary.
Yet even minor infections can quickly progress if you have cancer or are undergoing cancer treatment.
However, other factors can also cause abnormal WBC counts.
Cancer treatments, such as chemotherapy and radiation therapy, can lower your WBC count.
A high WBC count is usually resulting from infections or conditions that cause inflammation.
When the number of WBCs in your body is low, you are at a higher risk of infections.
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