Your blood is composed of many different types of cells that serve different functions. White blood cells are the cells that help the immune system fight infection. Neutrophils are a type of white blood cell that is important in fighting bacterial infections. The term neutropenia describes the medical condition when the number of circulating neutrophils in the blood is low. There are many different causes of neutropenia. The most common cause is cancer medications, including chemotherapy, which cause a temporary drop of neutrophils. Chemotherapy, in general terms, consists of medications that kill fast-dividing cells. Most of your body's cells do not grow or divide quickly. However, your white blood cells (neutrophils) do grow quickly. Depending upon the type of chemotherapy given, the neutrophils and other blood cells can be temporarily reduced, potentially leading to neutropenia. Diagnosing Neutropenia Your doctor can determine the number of neutrophils in your blood by ordering a simple laboratory test called a complete blood count with differential - often nicknamed "CBC with Diff." The total white blood cell count (WBC) is composed of multiple types of cells, such as neutrophils, lymphocytes, and basophils. The absolute neutrophil count (ANC) is the total number of neutrophils that are in the blood sample. Neutropenia exists when the ANC is less than 1,500. However, the risk of infection often doesn't begin to rise until the ANC is less than 1,000. The risk of infection is related to how low the ANC drops (also called the nadir) and how long the ANC remains low. The lower the neutrophil count drops and the longer the neutrophil count remains low, the higher the risk for infection becomes. Preventing Infections While your neutrophil count is low, it is important to reduce your risk for infection. The best way to reduce your risk of becoming ill is to wash your hands frequently, including before you eat and drink and before you touch your face. Let your family and friends know you are at risk for infection so they can be careful to limit your exposure to colds and other illnesses. Patients with neutropenia who are at high-risk for infection may be started on prophylactic antibiotics to prevent a serious complication. Most people who have neutropenia do not have long-term problems or complications from having low numbers of white blood cells. The good news is that you will likely have few, if any, symptoms from being neutropenic. The most common symptom is feeling tired. You should talk to your doctor about what your risk for neutropenia is and for the length of time you may have low neutrophil counts. You should also ask if any special precautions beyond hand washing should be taken. For most patients who receive chemotherapy, the drop in neutrophils is temporary. The bone marrow continuously makes blood cells, and after the chemotherapy effects fade, new blood cells are made and the neutrophil count returns to normal. Getting Treatment If your risk of neutropenia is very high, your doctor may recommend a shot such as Neulasta. This is a medication that tells the body to make new white blood cells to bring them back to normal levels faster than would naturally occur. The most important thing to remember is that if you develop a fever or infection when you may be neutropenic, seek immediate medical attention. Your body will have problems fighting an infection on its own, and prompt treatment of infections usually results in a quick and complete recovery from the infection. Marjorie Green, MD, is an oncologist specializing in breast cancer. Dr. Green practices at MD Anderson Cancer Center in Houston, Texas. She is a HealthGrades Recognized Doctor.