Filgrastim is used to stimulate the bone marrow to produce more white blood cells, which help the body fight infection. It is administered through daily subcutaneous injection, usually in the thighs or abdomen. Common side effects include bone and muscle pain, nose bleeds, fatigue, and pain at the injection site. The medication must be stored refrigerated and used within 7 days if removed from refrigeration. Proper administration involves cleaning the injection site, pinching the skin, inserting the needle at a 45 degree angle, and slowly injecting the contents of the syringe.