White blood cells (WBCs) fight infections from bacteria, viruses, fungi, and other pathogens (organisms that cause infection). One important type of WBC is the neutrophil. These cells are made in the 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 develop a low WBC count from the cancer or from treatment for the cancer. Cancer may be in the bone marrow, causing fewer neutrophils to be made. The WBC count can also go down when cancer is treated with chemotherapy drugs, which slow bone marrow production of healthy WBCs.
How Low Is Too Low?
When your blood is tested, ask for your WBC count and specifically, your neutrophil count. If your counts are 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
Prevent infections by taking the following measures:
When to Call the Doctor
If you have any of the following symptoms, call your health care provider:
- 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 Cancer Society website. Infections in people with cancer. www.cancer.org/treatment/treatments-and-side-effects/physical-side-effects/infections/infections-in-people-with-cancer.html. Updated February 25, 2015. Accessed May 2, 2019.
Centers for Disease Control and Prevention website. Preventing infections in cancer patients. www.cdc.gov/cancer/preventinfections/index.htm. Updated November 28, 2018. Accessed May 2, 2019.
Freifeld AG, Kaul DR. Infection in the patient with cancer. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE, eds. Abeloff's Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 34.
Review Date 4/21/2019
Updated by: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.