I strongly agree with the points others have made about how much acclimatization rates can vary person to person, but wanted to share/echo a couple of things that have helped me. I used to get severe headaches and puke fairly consistently above 13K, and still tend to feel rough my first day above 10K or so.
Taking more time really is the best solution (more on that below), but I get that it isn't always realistic. When I don't have time to properly acclimatize (I live in the Bay Area, sea level, but frequently do weekend trips to the Sierra), I've found that eating and drinking regularly, even when I don't feel hungry/thirsty, help keep the nausea at bay. Putting Gatorade or other drink mix in my water so that I'm getting calories even if I'm not able to eat quite enough also help tremendously. Finally, slowing WAAAY down is important. I love trail running and hiking fast, so this was/is a challenge, but I've learned that for me a pounding heart leads to a pounding head if I'm above 10K or so and haven't properly acclimatized. I try to set a goal of hiking smart rather than hiking fast -- like, instead of getting to X waypoint in Y hours, my goal is to get to X elevation still feeling good, then Y elevation still feeling good, etc.
I've used Diamox for especially challenging trips, and have found that it helps, but I still have to be careful about my exertion and nutrition/hydration. As others have noted, it's not magic, just something that can tip the scales a little more in your favor. I've found that the ONLY thing that allows me to get sloppy on nutrition or aggressive on pacing is spending several days at elevation. One other thing about Diamox -- it can actually dehydrate you, especially your first day on it, so make sure you're extra careful about hydration if you take it.
Spending several days at altitude can work wonders if you have the time, though. A couple of years ago I day-hiked the Whitney main trail twice a few weeks apart, no Diamox either time. First time was with a group of friends with only a night at Horseshoe Meadows before the hike. I summited, but had to go slower than most folks, and had a mild headache at the summit. The second trip came at the end of a week of backpacking and car camping/trail running ranging from 8,000 - 12,000 feet. I was over an hour faster on the ascent while feeling less tired, and didn't notice the altitude at all.
Hope at least some of this is helpful!
Edited by KaraKyrgyz (10/04/18 08:33 AM)