Leukocyte growth factors stimulate your body to make white blood cells. They're used to treat low white blood cell levels caused by chemotherapy or certain health conditions. Leukocyte growth factors are typically available as injectable medications. Examples include filgrastim (Neupogen, Zarxio, Nivestym), pegfilgrastim (Neulasta, Fulphila, Udenyca), and sargramostim (Leukine).