AltitudeAheadHow acclimatization works
How your body adapts to thinner air, how long it takes, and what helps.
Adapting to less oxygen
Acclimatization is the set of changes that let your body work with less oxygen. Within hours you breathe faster and deeper. Over the following days your kidneys rebalance your blood chemistry so you can keep breathing more, and your heart and circulation adjust. Over weeks, your body makes more red blood cells.
These changes take days. That is why gaining altitude gradually matters more than how fit you are.
Acclimatization is step by step
Being acclimatized to one altitude doesn't mean you are acclimatized to a higher one. Each significant gain in sleeping altitude needs new adaptation.
Acclimatization is also lost: after days to weeks at low altitude, much of it fades.
What helps
A gradual increase in sleeping altitude, extra nights at the same altitude, and time spent at moderate altitude before a trip all help. Staying hydrated, eating enough and avoiding overexertion in the first days at a new altitude support your body, but they don't replace a gradual ascent.
Medication can be used to help prevent altitude illness in some situations. Whether it's right for you, and how to take it, is a question for a doctor before your trip.
Everyone is different
People acclimatize at different speeds, and the same person can react differently on different trips. Listen to your body and to the people around you — not only to the plan.
General information, not medical advice. If you have symptoms at altitude, don't go higher. See the medical disclaimer.
