A substance that stimulates the bone marrow to make more red blood cells. Erythropoiesis-stimulating agents are used to treat anemia caused by chronic kidney failure, some anticancer drugs, and certain treatments for HIV. They may also be used to lower the number of blood transfusions needed during and after certain major surgeries. Examples of erythropoiesis-stimulating agents are epoetin alfa (Epogen, Procrit) and darbepoetin alfa (Aranesp). Also called ESA.