Neupogen is a medication that helps stimulate the production of white blood cells in the body. It is primarily used to treat patients undergoing chemotherapy, as these treatments can lower white blood cell counts, increasing the risk of infections. By boosting white blood cell levels, Neupogen helps improve the immune system's ability to fight off infections. This medication is administered through an injection, either under the skin or into a vein. Common side effects may include bone pain, headache, and fatigue. Patients should discuss any concerns with their healthcare provider to ensure safe and effective use of Neupogen.