How to Acclimatise at Altitude: 5 Top Tips


, by Charlie Boscoe

High alpine base camp. Photo: Vixit, Shutterstock

Climbing a mountain of any height is a challenge, but add thinner-than-normal air into the equation, and things get really tough. What might be an easy glacial hike at relatively modest altitudes can quickly become a sufferfest if you're high up and unacclimatised.

Honestly, a bit of suffering is all part of the high altitude experience, but minimising it not only increases your chances of success but your enjoyment too. I used to work as an expedition leader in the Himalayas and Andes, so I saw plenty of people trying to acclimatise, and I can assure you that getting it right is a lot more fun than screwing it up!

In this article, I'll run through my top 5 tips for acclimatising to altitude (none of which are a magic bullet and some of which might not be possible given your schedule), and hopefully, you'll be able to use them where and when you can. Consider it like healthy eating—just get the basic stuff right and cut a corner occasionally when circumstances dictate. There's no getting around the fact that going to altitude is hard, but it's also immensely rewarding when you get it right. It allows you to see things few people are ever lucky enough to glimpse. It doesn't come easy, but nothing worth having ever does.

The moment it all pays off - me with Skalzang Rigzin on the summit of Lungser Kangri (6666m), Ladakh, India. Photo Boscoe Collection.

So on that philosophical note, here are my top 5 tips for acclimatising:

1. Gooooo slooooowly

Rushing up to altitude is the number one reason why people fail in their objective or "succeed" (is it really success if it nearly kills you?!?!), but only after taking unnecessary risks and enduring a whole lot of pain. Going to altitude (anything over 3,000ish metres/10,000 feet) demands a lot of your body, and asking its permission to proceed higher is much more pleasant than begging its forgiveness for having gone too high!

Make your acclimatisation schedule as long as you can, and you'll reap the benefits. A good rule of thumb is—once above 3000m—to only increase your sleeping altitude by 300m per night, and to take an extra night every third height increase. For example, if you sleep your first night at 3000m, sleep your second at 3300m, your third AND fourth at 3600m, and then push on to 3900m on your fifth night. 

Unfortunately for us, mountains and valleys are rarely lined up such that you can dictate your schedule quite this accurately, but you get the gist—go slowly and pause regularly. Trust me—your body will quickly let you know if you ascend faster than it would like!

Taking our time on the way up Kilimanjaro’s Rongai Route. Many parties rush up Kilimanjaro, making it a far more dangerous mountain than it ought to be. Photo Boscoe Collection.

2. Climb high, sleep low

When you climb to a new high point, your body takes a few hours to realise what is being done to it, so you can actually sneak up high and then descend back to a relatively modest sleeping altitude without paying a high price. Spending a whole evening and night at a new altitude is physically taxing, but sleeping down in the valley for a few nights and using the days to trek up high is a great—and relatively pain-free—way to acclimatise. 

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If you stick to the sleep schedule suggested in tip 1, then using that day between your third and fourth nights to trek to 4000m-ish before returning back down to your campsite is an excellent way to gain some more red blood cells and prepare you for the days to come. Even if there are no obvious summits or passes above your camp, just hike up 500 vertical metres, eat lunch somewhere with a nice view, and then return to camp—your body will thank you for it in the long run!

This is what it looks like when you rush your acclimatisation….me paying the price at Pequeno Alpamayo base camp, Bolivia. Photo Boscoe Collection.

3. Drink a LOT of water

"A good mountaineer always pees clear!" Drinking as much water as you reasonably can will help you acclimatise for several reasons. Firstly, the air at higher altitudes tends to be drier, and the lower humidity can lead to increased water loss through respiration and sweating. As a result, you are more likely to become dehydrated if you don't replenish the lost fluids by drinking enough water.

Second, when you ascend to higher altitudes, your body adjusts to the lower atmospheric pressure by increasing your breathing rate. This can stimulate an increase in urine production, leading to more frequent urination. Consequently, you need to drink more water to compensate for the increased fluid loss.

Finally, staying well-hydrated improves blood circulation and ensures efficient oxygen transport throughout your body. Water plays a crucial role in maintaining adequate blood volume and preventing its thickening, which could impede oxygen delivery to various organs and tissues. Sufficient hydration helps optimize your body's ability to adapt to the lower oxygen levels at high altitudes.

As if those weren't good enough reasons, staying hydrated will also make you more comfortable, because the symptoms of dehydration (headaches, nausea, fatigue, and dizziness) are the same as many of those which result from acute mountain sickness (AMS). If you are suffering a bit with the altitude, being hydrated will at least mean that you're not compounding your pain with dehydration.

4. Let your body do its work

When you go to altitude, it can feel as if you're doing very little real exercise and that you must be losing fitness, but this is deceptive. Many keen climbers who go to altitude feel like the trekking days during the acclimatisation period are too easy, and they supplement them with pullups and pushups in the evening. I know because I used to be one of them—until I realised that simply existing in rarified air is physically taxing enough and that adding to the strain isn't going to help at all.

Yes, you'll probably lose some muscle mass, and your strength will decline after a period at altitude, but that's part of the deal, and you signed up for it! If you want to maintain your conditioning, then a trip to altitude isn't for you. By deciding to go into thin air, you have to accept all that comes with it, and doing relatively little exercise is just something you have to accept while your body gets used to the shock you've inflicted on it!

Losing a bit of strength is worth it for a view like this. The summit of Mera Peak, Nepal, with Everest and Makalu behind. Photo Boscoe Collection.

5. Bail

If you're not acclimatising as you wish, and you don't think you can do what you're hoping to—bail. There is very little to be gained and a lot to lose if you decide to push on even after it's become clear that you're not going to achieve your goal safely.

I had a client on a trekking trip once who was clearly suffering from the altitude but was stubbornly refusing to discuss it and insisted that he was fine. It was obvious that he was struggling, but he seemed to be coping right up until the moment when I was walking behind him and he suddenly collapsed and started gasping for air. Luckily we had a strong Sherpa team, and they were able—over the course of several hours—to get him down the valley to a village we'd stayed in previously, but it turned what would have been a disappointing but sensible decision to bail into a potentially very dangerous situation. If it's not happening, accept it and go do something else for the rest of your trip. As the late, great Don Whillans said, "The mountain will be there next year—the trick is to make sure you are!"

If all this talk has got you fired up for some high-altitude adventures, check out our guidebooks to the Everest Base Camp Trek, Aconcagua (the world’s highest mountain outside Asia), and Kilimanjaro’s Machame Route.