How to Acclimatise to High Altitude
Altitude is the single biggest physical variable on an Andean or Himalayan journey — and the most manageable. Here is how the thin-air world works, and the simple habits that let you enjoy it.
Stand in the Plaza de Armas in Cusco and you are already higher than almost any peak in the Alps. The Andes, the Bolivian altiplano and the Himalaya all ask the same quiet question of a traveller arriving from sea level: can your body do its work on a third less oxygen? The reassuring answer is that almost everyone can — given a little time and the right habits.
Acclimatisation is not a test of fitness or willpower. It is a physiological process, and it runs on its own schedule. Understand what is happening inside you and the high country stops being a hurdle and becomes simply another landscape — one of the most beautiful on Earth.
What altitude actually does to the body
The air at 3,400 metres is not poorer in oxygen by proportion — it is still about 21 percent. There is simply less of it, because the air pressure is lower, so every breath delivers fewer oxygen molecules to your blood. At Cusco that means roughly 32 percent less oxygen per breath than at sea level; on the Uyuni altiplano, closer to 40 percent less.
Your body responds quickly and intelligently. Within hours you breathe a little faster and deeper; within days your kidneys adjust your blood chemistry and your bone marrow begins producing more oxygen-carrying red cells. This is acclimatisation, and it is why a few patient days at altitude make such an enormous difference.
Recognising altitude sickness
Acute mountain sickness (AMS) is common, usually mild, and not dangerous if respected. Its signature is a headache, often with some combination of fatigue, poor appetite, nausea, light-headedness and broken sleep. It typically appears six to twelve hours after arriving high and eases over a day or two as you adjust.
The golden rule is simple: never ascend to a higher sleeping altitude while you have symptoms of AMS. Mild AMS is a signal to pause, not to push. The rare but serious conditions — fluid on the lungs or the brain — are almost always preceded by ignored AMS, which is exactly why our guides monitor every traveller daily.
The habits that genuinely work
Ascend gradually and, where you can, climb high but sleep low — spend your day at altitude and your night a few hundred metres below it. Drink far more water than feels necessary, because the dry mountain air dehydrates you invisibly. Favour carbohydrates, which the body metabolises more efficiently on less oxygen, and go easy: no alcohol for the first days, and no hard exertion on day one.
Coca tea, offered everywhere in the Andes, is a gentle and traditional aid. Above all, build in a rest day on arrival — the single most effective thing any traveller can do — and resist the urge to treat your first high day as a sightseeing sprint.
How we pace a journey for altitude
A well-built itinerary does much of the work for you. On Andes to Antarctica we deliberately ascend in steps — a few days in Cusco, then nights spent lower in the Sacred Valley, where the air is kinder, before any demanding day. Machu Picchu itself, at 2,430 metres, is lower than Cusco, so by the time you reach it you are already adjusted.
This is why we never sell a one-day dash to high country. The mountains reward the traveller who arrives slowly, and an itinerary that respects acclimatisation is not a constraint — it is the difference between enduring the Andes and loving them.
Medication, and when to seek help
Acetazolamide (Diamox) can speed acclimatisation and is widely used; whether it is right for you is a conversation to have with your own doctor before departure, along with any existing heart or lung conditions. Our medical questionnaire flags anything worth discussing.
On the journey itself, the rule never changes: if symptoms are severe or worsening, the treatment is to descend, and to descend promptly. Our guides carry oximeters and oxygen and have the experience to make that call early — but descent, not stubbornness, is always the cure.
Quick answers
How long does it take to acclimatise to high altitude?
Most travellers feel substantially better within two to three days at a given altitude, and well-adjusted within about a week. Full acclimatisation — including the rise in red blood cells — continues for several weeks, but you do not need to wait that long to feel good. A rest day on arrival and a gradual ascent thereafter are what matter most.
Should I take altitude medication?
Acetazolamide can help and is commonly used, but it is a personal medical decision: discuss it with your own doctor before you travel, especially if you have any heart, lung or kidney condition or a sulfa allergy. It is a preventive aid, not a substitute for sensible, gradual ascent.
Who should be cautious about travelling to high altitude?
Most healthy travellers, including children and older adults, acclimatise well. People with significant heart or lung disease, uncontrolled high blood pressure, or sickle cell disease should seek medical advice first. Pregnancy and recent altitude illness also warrant a conversation with a doctor. Our pre-departure medical form exists precisely to surface these questions early.
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