I've been to Nepal a few times and started feeling AMS symptoms about 1-2 hours after arriving at our lodge in Namche. Diamox kept me going great for the nxt few days on our way to Tengboche where we maxed out about 13k feet, besides the heli flight back to Lukla. Similar symptoms even at a ski resort at 9k feet in the US. It's "not that high" but plenty high to induce AMS.