when i was first trying out ultralight
had been really jonesing for a backpack & had to squeeze in a quick weekend trip, plus monday
left the house (sacramento - so sea level) much later saturday morning than planned, drove to trailhead (Rock Creek, so pretty high to start - around 9000ft) & started right in hiking, making much faster and easier time due to my new ultralight load. soon found myself pushing on, off trail, through steep, rocky & bouldery 'scape with a fair amount of snow in the shady areas. set up camp next to a lake a bit over 11000 ft - probably a very quick 8 miles in and about 1.5 off trail. didn't notice at first, but i was showing some signs as i set up camp, got water, made dinner, etc. but by the time dinner was done, i was obviously not thinking clearly, lacking coordination (more lacking than usual) & had to force myself to eat my meal. then the weakness and nausea was really starting to set in. so i jumped in bed, hoping rest after the meal would be enough. a couple hours into the night, though, and it was clear that i was still going downhill (figuratively), so i decided i'd better do so literally while i still had legs to stand on. had some uncomfortable discharges from various openings along the way down, but managed to drop about 1500 ft & was about to literally drop myself. jumped in bag & bivy right next to the trail so someone would find my body next morning worst case. was still feeling sick, but the 1500 ft seemed to tip the sand to start balancing out the right way, gradually.
slept like a stone.
woke up, looking forward to some hot tea and breakfast, then realized if i wanted it, i'd have to hike back up to where i'd left my stove and pot. feeling still a bit ill and quite a bit weak, just walked out last couple miles with tail between legs. my friend's son in law (they live in mammoth) followed my directions up, though, and came back with my pot & stove, refusing my offer of both or one of the found pieces of equipment in return for his effort.
now i always, always, always remember the rule i'd already made for myself: always sleep at least one night at high elevation before starting a high elevation trip. last couple longer trips i've actually done 2-3 nights camping around 9-10,000 ft before starting (one partway place that's good is campground at mt. rose - i also like to stop on the way to s. sierras & stealth camp off the road up on monitor pass).