White Blood Cell Count and Cancer: What You Need To Know

Cancer is a condition where abnormal cells divide quickly, disrupting the function of organs and tissues in your body. Cancer in the bone marrow, the spongy part of your bones that produces white blood cells (WBCs), can reduce the number of WBCs, which are immune system cells that fight pathogens in your body. They can also be damaged by treatments like chemotherapy and radiation. As a result, you may have a low white blood cell count, which is also known as leukopenia.

Hand holding blood sample in laboratory

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What Are White Blood Cells?

There are several types of white blood cells (WBCs), also called leukocytes, and each can be affected differently by cancer and its treatments. There are five types of white blood cells:

  • Neutrophils attack viruses and bacteria.
  • Eosinophils fight bacteria, parasites, and mount immune responses to allergens.
  • Basophils create generic immune responses and play a role in conditions like asthma.
  • Lymphocytes help defend and fight against infection. There are two main types of lymphocytes: T-cells and B-cells. T-cells target infectious invaders, while B-cells create antibodies to prevent future infections.
  • Monocytes clean up wastes and dead cells in the body.

Cancer can lead to a high or low WBC count, depending on the type of cancer, which type of white blood cell is affected, and where the cancer is in your body.

What Causes a Low White Blood Cell Count?

A low white blood cell count can develop as a result of cancer or cancer treatment. You may also be given a more specific diagnosis based on the exact type of white blood cell affected like neutropenia, which is a low number of neutrophils.

Low Blood Counts From Cancer

Some cancers develop in the blood and bone marrow, and these cancers can prevent your body from making new white blood cells.

Cancer can also cause your body to make abnormal white blood cells that don't function as they should in your immune system.

Cancers that affect white blood cells include blood and bone marrow cancers like:

Low Blood Cell Counts From Cancer Treatments

Treatments for cancers can also lead to a drop in the number of WBCs in your blood. Medications like chemotherapy disrupt how rapidly growing cells such as cancer cells reproduce. It can also damage healthy cells like white blood cells. Radiation therapy, another common cancer treatment, works in much the same way and can also lead to a drop in white blood cell counts.

In many cases, a low white blood cell count caused by cancer treatments is temporary. Blood cell counts will usually return to normal levels once the treatment ends.

Can Cancer Cause a High White Blood Cell Count?

While infections and inflammation are more often to blame for an increase in white blood cell counts, some cancers can increase your WBC count as well. This condition, called leukocytosis, can occur in some of the same cancers that cause WBCs to drop, like leukemia and lymphoma. Leukemia and lymphomas can cause out-of-control reproduction of some types of blood cells. When there are too many white blood cells, they can crowd out healthy cells and disrupt normal function and cell production.

Preventing Infections

Since white blood cells help defend your body against pathogens, too few WBCs can increase your risk of infections. For people with cancer, their risk of infection is even higher due to weakness, nutrition problems, and other side effects of cancer and cancer treatments.

However, you can take steps to reduce your risk of infection during cancer treatment, and your medical team will monitor your blood counts throughout the process. Some tips for staying infection-free while undergoing cancer treatment include:

  • Wash your hands frequently, especially after you have been in public places
  • Use cleaning wipes on high-touch surfaces like doorknobs
  • Wash fruits and vegetables thoroughly
  • Avoid crowds, especially during cold and flu season
  • Wear gloves when gardening or caring for animals
  • Bathe or shower daily
  • Check your skin regularly for cuts and sores
  • Clean even small cuts well and treat them with antibiotic ointment
  • Brush your teeth often
  • Avoid public swimming pools or bathing areas
  • Get vaccinations for things like the flu, but avoid live vaccines

Even minor infections can quickly progress if you have cancer or are undergoing cancer treatment. Be sure to discuss prevention strategies, and any signs of infection like fever, chills, and body aches with your doctor. Severe infections can lead to sepsis, which occurs when chemicals meant to attack pathogens cause widespread inflammation in your body.

Summary

Cancer and treatments used to treat cancer, such as chemotherapy and radiation therapy, can lower your WBC count. White blood cells are immune system cells that help defend your body against foreign threats like viruses and bacteria. When the number of WBCs in your body are low, you are at a higher risk of infections. It's important to work closely with your doctor to monitor your blood cell numbers and come up with strategies to prevent infections if you have cancer or are going through treatment for cancer.

A Word From Verywell

Some cancers can cause your white blood cell count to increase, but more often it reduces the number of these cells. WBCs power the immune system, and both cancer and cancer treatments can reduce the number of these cells that you have available to fight infection. If you have cancer, are undergoing cancer treatment, or have a low WBC count, you will need to take precautions to prevent infections.

Frequently Asked Questions

Do all cancers raise white blood cell count?

No. Bone marrow and blood cancers, in particular, can lead to high blood counts as the cancer cells cause blood cells to reproduce rapidly.

Does a high white blood cell count indicate cancer?

Not always. A high white blood cell count could signal certain types of cancer, such as leukemia or lymphoma, but it more often is a sign of inflammation or infection. When there is a pathogen in your body, 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.

What is a dangerous white blood cell count?

It can vary by age and gender, but you are considered to have a low white blood cell count with less than 4,500 white blood cells per microliter of blood. The lower this number goes, the more susceptible you are to infections.

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7 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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  2. Johns Hopkins Medicine. Blood and bone marrow cancer basics.

  3. MedlinePlus. Low white blood cell count and cancer. Updated April 21, 2019.

  4. Leukemia and Lymphoma Society. Understanding blood counts.

  5. Cleveland Clinic. High white blood cell count. Updated January 12, 2018.

  6. Cleveland Clinic. Leukemia. Updated November 19, 2019.

  7. Centers for Disease Control and Prevention. Staying healthy during cancer treatment. Updated May 12, 2021.