One of the ME/CFS specialists said that in his experience, 5000 feet was about where his patients did best. I am at 5000 ft and didn't have any problem adjusting from sea level.
@Sushi ... Wow... Really? ( Shoot, I could be in MX now rather than snowbound up north). That's surprising.
I had a rough time at 20 working at a camp at 10,000', and I was a distance runner then.
When I was 49 and had been sick about 7 years I spent a summer in Casper WY. I could only function by taking oxycodone without constant air hunger. I've always lived at Sea level.
I read some discouraging threads here about people trying to just get across the Rockies to the low Sonoran desert.
I was looking into trying Lake Chapala MX on the advice of women alone over 55 who had been there. That was 2016. I'd been well three years. It's at about 5-6000'.
The reason I didn't try was because I kept coming across articles about how badly neurological diseases do at high elevations.
I knew I had neuropathies, balance issues, vision problems and Lyme. Wasn't thinking about CFS.
(Have you always lived at high elevations?)
Btw, at the camp when I was 20, I was the most fit woman, but sicker than anyone else; even the middle aged visitors from the East. Finally after 4 months I could run and felt really good.
I had POTS from about 7-30. Really severe as a child and teen. Maybe it's an inherent thing in some people?