White blood cells fight infections from bacteria, viruses, and fungi. One type of white blood cell is the neutrophil. These cells are made in bone marrow and travel in the blood. They sense infections, move toward the germs, and kill them.
It is called a low white blood cell count, or neutropenia, when a person has too few neutrophils. This makes it harder for the person to fight off germs, and more likely to get sick from infections. In general, an adult with who has fewer than 1700 neutrophils in a microliter of blood has a low white blood cell count.
If the white blood cell count is very low, (fewer than 500 neutrophils in a microliter of blood), it is called severe neutropenia. When the neutrophil count gets this low, even the bacteria normally living in a person’s mouth, skin, and gut can cause infections.
Why it occurs
A person with cancer can get a low white blood cell count from the cancer or from treatment for the cancer. Cancer may be in the bone marrow, causing fewer neutrophils to be made. The white blood cell count can also go down when cancer is treated with chemotherapy drugs that kill fast growing cells. White blood cells also grow quickly, so the treatment can attack the white blood cells as well as the cancer.
Other causes of a low white blood cell count include:
- Crohn's disease
- Infections, such as tuberculosis (TB) or certain viruses like HIV
- Lupus (also called systemic lupus erythematosus)
- Rheumatoid arthritis
- Some medicines, such as those that treat infections, high blood pressure, or seizures
How low is too low?
When your blood is tested, ask for your white blood cell count. When your white blood cell count is low, do what you can to prevent infections. Know the signs of infection and what to do if you see them.
When to call the doctor
If you have any of the following symptoms, call your doctor:
- Fevers, chills, or sweats. These may be signs of infection.
- Diarrhea that does not go away or is bloody.
- Severe nausea and vomiting.
- Being unable to eat or drink.
- Extreme weakness.
- Redness, swelling, or drainage from any place where you have an IV line inserted into your body.
- A new skin rash or blisters.
- Pain in your stomach area.
- A very bad headache or one that does not go away.
- A cough that is getting worse.
- Trouble breathing when you are at rest or when you are doing simple tasks.
- Burning when you urinate.
Neutropenia and cancer; Absolute neutrophil count and cancer; ANC and cancer
What you need to know: neutropenia and risk for infection. Centers for Disease Control and Prevention Web site. http://www.cdc.gov/cancer/preventinfections/pdf/neutropenia.pdf.Accessed July 29, 2013.What you need to know: neutropenia and risk for infection. Centers for Disease Control and Prevention Web site. http://www.cdc.gov/cancer/preventinfections/pdf/neutropenia.pdf. Accessed July 29, 2013.
Managing chemotherapy side effects. Nation Cancer Institute Web site. http://www.cancer.gov/cancertopics/coping/chemo-side-effects/infection.pdf.Accessed July 29, 2013.Managing chemotherapy side effects. Nation Cancer Institute Web site. http://www.cancer.gov/cancertopics/coping/chemo-side-effects/infection.pdf. Accessed July 29, 2013.
Neutropenia and risk of serious infection. American Cancer Society Web site. http://www.cancer.org/treatment/treatmentsandsideeffects/physicalsideeffects/infectionsinpeoplewithcancer/infectionsinpeoplewithcancer/infections-in-people-with-cancer-neutropenia-and-infection-risk.Accessed July 29, 2013.Neutropenia and risk of serious infection. American Cancer Society Web site. http://www.cancer.org/treatment/treatmentsandsideeffects/physicalsideeffects/infectionsinpeoplewithcancer/infectionsinpeoplewithcancer/infections-in-people-with-cancer-neutropenia-and-infection-risk. Accessed July 29, 2013.
Berliner N. Leukocytosis and Leukopenia. In: Goldman L, Ausiello D, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 170.
Update Date 5/13/2013
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.