Erythropoietin is a hormone produced primarily by the kidneys that plays a crucial role in the production of red blood cells. When oxygen levels in the blood are low, the kidneys release erythropoietin into the bloodstream, stimulating the bone marrow to increase the production of red blood cells. This process helps improve the oxygen-carrying capacity of the blood. Erythropoietin is also used as a medication to treat certain types of anemia, particularly in patients with chronic kidney disease or those undergoing chemotherapy. By boosting red blood cell production, it helps alleviate symptoms of fatigue and weakness associated with low red blood cell counts.