Blood doping is an illegal method of enhancing athletic performance by artificially increasing the bloods ability to transport oxygen to muscles. This can be achieved by increasing the number of red blood cells in the bloodstream, which carry oxygen from the lungs to the muscles. Blood doping can be done in several ways, including:

• Blood transfusions: Infusing additional red blood cell volume or whole blood from another person or back to the same individual.

• Erythropoietin (EPO): A hormone that stimulates the production of red blood cells.

Blood doping is banned by the World Anti-Doping Agency (WADA) and other sports organizations. It can improve an athletes aerobic capacity and endurance, as well as improve recovery, particularly in long-distance events such as running and cycling. However, blood doping can also cause serious health risks, such as blood clots, stroke, and heart attack.

There are tests to detect some types of blood doping, but not all. For example, blood doping via homologous transfusion can be detected by testing, while no test exists to directly detect autologous transfusions. Indirect methods are used to detect autologous transfusions, such as comparing an athletes blood profile at testing time to blood samples collected at previous times.