White blood cells fight infections from bacteria, viruses, fungi. and other pathogens (organisms that cause infection). One important type of white blood cell is the neutrophil. These cells are made in bone marrow and travel in the blood throughout the body. They sense infections, gather at sites of infection, and destroy the pathogens.
When the body has too few neutrophils, the condition is called neutropenia. This makes it harder for the body to fight off pathogens. As a result the person is more likely to get sick from infections. In general, an adult who has fewer than 1,000 neutrophils in a microliter of blood has neutropenia.
If the neutrophil 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 serious 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, which slow bone marrow production of healthy white blood cells.
Other causes of a low white blood cell count include:
- Crohn 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 and specifically, your neutrophil. 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 have them.
What you can do to Prevent Infections
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
American Cancers Society. Infections in people with cancer. Revised February 25, 2015. www.cancer.org/acs/groups/cid/documents/webcontent/002871-pdf.pdf. Accessed August 19, 2015.
Centers for Disease Control and Prevention. What you need to know: neutropenia and risk for infection. www.cdc.gov/cancer/preventinfections/pdf/neutropenia.pdf. Accessed August 19, 2015.
Freifeld AG, Kaul DR. Infection in the patient with cancer. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2014:chap 36.
National Cancer Institute. Managing chemotherapy side effects: infection. Revised February 2012. www.cancer.gov/cancertopics/coping/chemo-side-effects/infection.pdf. Accessed August 19, 2015.
Update Date 5/4/2015
Updated by: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.