Any properly typed red blood cells may be used for blood doping, but in most cases, the athlete's own blood is used. The patient donates a pint of blood, which is then put through a centrifuge to separate the red blood cells from the rest of the plasma. After the patient's red blood cell level has recovered normally, the separated red blood cells are re-injected into the patient.
Blood doping allows the body to be supplied with more oxygen, and therefore increases endurance and lessens fatigue. It is therefore used by long distance athletes, such as cyclists and marathon runners. However, it is not without danger. Although it is natural for persons living at high altitude to have high levels of hemoglobin, for the most part high hemoglobin levels can lead to excessive clotting. In addition, the needles used for doping often harbor infections.