Just go and live in Denver for a month or so. That will increase your hematocrit (or your # of red blood cells) At high altitudes there is less oxygen available for the lungs(decreased Barimetric pressure lowers gas pressures) so the body compensates by producing more red blood cells. This will normalize over time when you return to sea level. Ever wonder why the Kenyans are so dominant in running? They run at high altitude and do lots of hill/mountain climbing/running.