Filgrastim injection products (Granix, Neupogen, Nivestym, Releuko, Zarxio) are used to decrease the chance of infection in people who have non myeloid cancer (cancer that does not involve the bone marrow) and are receiving chemotherapy medications that may decrease the number of neutrophils (a type of blood cell needed to fight infection). Filgrastim injection products (Neupogen, Nivestym, Releuko, Zarxio) are also used to help increase the number of white blood cells, and decrease the length of time with fever in people with acute myeloid leukemia (AML; a type of cancer of the white blood cells) who are receiving treatment with chemotherapy medications. Filgrastim injection products (Neupogen, Nivestym, Releuko, Zarxio) are also used in people who are undergoing bone marrow transplants and in people who have severe chronic neutropenia (condition in which there are a low number of neutrophils in the blood). Filgrastim injection products (Neupogen, Nivestym, Zarxio) are also used to prepare the blood for leukapheresis (a treatment in which certain blood cells are removed from the body. Filgrastim injection (Neupogen) is also used to increase the chance of survival in people who have been exposed to harmful amounts of radiation, which can cause severe and life-threatening damage to your bone marrow. Filgrastim is in a class of medications called colony-stimulating factors. It works by helping the body make more neutrophils.