A lot has to do with your age, physical condition, weight and preparation. If you are out of shape, get back into shape.
It's all about the heart and lungs being able to keep your body supplied with good blood and oxygen flow.
If you have any doubt, see your doctor and tell him/her what you want to do.
I hunted the Rockies in Montana at 8000 ft. Coming from an area of 500-600 ft above sea level I had to prepare myself for that altitude. Being on foot a lot it was strenuous as all he!! even though I was prepared.
Trust me when I tell you there were times we were chasing game around and I thought my lungs were going to bust and my heart was going to rip out of my chest.
I was younger and stronger at the time and in pretty good shape. I never got sick or lost my appetite.
I had so much fun I went back a couple of more times.