If your ANC is below 500 for an extended period of time, your risk of serious bacterial infection may increase significantly. A low neutrophil count is also called neutropenia . Neutrophils die continuously from age or from fighting infections, and your bone marrow must make new neutrophils to replace them. When something reduces the production of neutrophils in your bone marrow, the neutrophil count will drop and may eventually be low enough to become dangerous. Common causes of reduced neutrophil production are medications, infections, and tumors.
Prescription medications are the most frequent cause of neutropenia.
In almost all cases, medication-induced neutropenia resolves after the drug is stopped or its dosage is reduced. Infections can cause neutropenia directly by infecting the bone marrow or indirectly through the release of chemicals that block production of cells. HIV infection itself may also cause neutropenia, but other possibilities need to be excluded. Tumors such as lymphoma that grow in the bone marrow are another potential cause of neutropenia. A low neutrophil count is diagnosed by a blood test called a complete blood count .