Altitude affects everyone differently. I live below sea level. I am typing this at 9300 feet. Other than very mild headaches, I suffer no ill effects. Obviously my lungs take a while to acclimate. My wife does well when she first arrives, then at about the 2 week mark starts suffering fatigue, shortness of breath and headaches.
All of the suggestions given are good and may work for some or even most people, but some folks simply can't overcome the effects.
