Once you are acclimatized to a certain height, how long will you stay acclimatized, is that a few days for such an altitude, a week or can you go up a high mountain for a month after you have been up to 4000 m without having to acclimatize again? And if, for example, I climb a 7000 m mountain in the Himalayas, after a descent I can climb another 7000 m mountain a week later without acclimatizing without being bothered by altitude sickness?
Answer by dr. Han Willems,
our expert in the field of altitude sickness:
The answer to your question is two-fold. Acclimatization disappears just as quickly as you build it up. Building up a reasonable acclimatization at 7000 meters takes longer (usually at least two to four weeks, but that is very different per person), so that you go more gradually to that height than to 4000 meters, that can be reasonably safe within a week. Are you well acclimatized at 7000 meters and then descend again, and then you return to that height within a week, then you have lost some of your acclimatization but not everything.
Theoretically, you could therefore go up faster with a lower risk altitude sickness. But, and that is two-fold, because the same person does not respond the same every time, it also gives such acclimatization no guarantee and so you would be pretty big anyway altitude sick could be. After about three weeks at low tide, a person acclimatised at 7000 meters must again consider himself not acclimatized and then the same risks apply as with a new ascent. Acclimatization at 4000 meters obtained in a week also disappears after descending within a week. If you stay at 4000 meters for much longer (weeks), de-acclimatization will also take longer, but the following also applies: after about three weeks you should consider yourself not acclimatized and the entire adjustment process starts again at the beginning.