Altitude sickness usually happens above 13,000 feet

based on our hiking experience. Two of our hiking team members always had a vomitting problem at above 13,000 feet. I didn't feel anything when hiking at those 14ers except that my heart beat very very fast.

Lasa is about 3,700 meters (a little above 12,000 feet)above sea level, which is actually not that bad. However, one would have altitude sickness if he/she suddenly go there from a place at a low altitude. 纳木措 is about 4,700 meters (above 15,000 feet) above sea level where I felt sharp headache and my lips became all purple. The highest altitude I have been to was 唐古拉山口 (5,500 meters or >18000 feet above sea level). I was sleeping in a bus when I passed 唐古拉山口. I remember I felt out of breath in my dream.