When you move to higher elevation, the air contains less oxygen. Your body senses this over time and releases a chemical messenger to your bone marrow to produce more red blood cells...the region of your body that produces this messenger is the kidneys, and the messenger chemical is called erythropoietin (EPO for short hand).
There is synthetic EPO, which would help you prep for a high altitude hunt, but the stuff comes with risks (clotting) and requires a prescription. It is also a high cost med.
You can read up on this via google search...and learn all about how and why it works.
Generally speaking, I think your best best is to be in good physical shape, then go high and stay there for as much time as possible before your hunt..... the meds are just too much risk IMO.
