Erythropoietin (EPO) is a hormone produced by the kidneys that stimulates the production of red blood cells in the bone marrow. In medical contexts, synthetic EPO is used to treat anemia, particularly in patients with kidney disease. In sports, it is a banned performance-enhancing drug due to its ability to increase oxygen-carrying capacity and endurance.
but like let's if they're not testing for EPO for example
""Discussed in the context of doping and performance enhancement, and how it's detected."