Neulastim Injection is used for Abnormally low white blood cell count, Fever and infection due to neutropenia in patients receiving chemotherapy, Chronic myeloid leukemia, Cancer in which the bone marrow does not make enough healthy blood cells and other conditions. Neulastim Injection may also be used for purposes not listed in this medication guide. Neulastim Injection contains Pegfilgrastim as an active ingredient. Neulastim Injection works by increasing the production of red blood cells, white blood cells, and platelets.