Acclimatisation on Kilimanjaro

Acclimatisation is the whole game on Kilimanjaro. It is the difference between a hard but achievable week and a miserable one that ends at 5,100 m, and it is very largely determined before you arrive — by the itinerary you booked.

The governing principle has a name that sounds like a slogan and is actually a mechanism: climb high, sleep low.

Sleeping altitude is the number that matters

Your body adapts in response to the altitude it rests at, not the altitude it briefly touched. Walking to 4,600 m at lunchtime gives the stimulus; sleeping at 3,960 m gives the recovery in which the adaptation actually happens.

This is why day four of a well-designed Lemosho itinerary — up to Lava Tower at 4,630 m, then down 670 m to sleep at Barranco — is the most valuable day of the trek despite gaining only sixty metres net.

How to read an itinerary properly

Ignore the day count for a moment. Write down the altitude you sleep at each night and look at the shape of the list.

• A straight line upward from 2,800 m to 4,700 m with no dips is asking a great deal of your body.
• A profile that rises and falls, with two nights somewhere in the 3,500–4,000 m band, has been designed by somebody thinking about physiology rather than logistics.

Our eight-day Lemosho sleeps at 2,785, 3,505, 3,900, 3,960, 3,995 and 4,673 m. Five of the six nights are below 4,000 m. That is the argument for the route in a single line of numbers.

The rules of thumb, and their limits

High-altitude guidance generally suggests not increasing sleeping altitude by more than roughly 300–500 m per night above 3,000 m, with a rest day every 1,000 m or so.

Kilimanjaro breaks this. Almost every commercial itinerary gains altitude faster than the conservative guidance, because a truly conservative ascent would take two weeks and nobody sells it. That is not a scandal — it is why the mountain has the summit success rates it does, and why the difference between six days and nine days is so large.

Understanding that helps you make the real decision: within a compressed schedule, buy every extra night you can.

What you can do on the mountain

The itinerary does most of the work, but these genuinely help:

1. Walk slower than feels natural. Your guides will say pole pole until you are sick of hearing it. They are right, and the people who ignore it in the first three days are the people struggling on day five.
2. Drink far more than you want to. Three to four litres a day. You will urinate constantly and that is the point.
3. Eat even without appetite. Appetite falls sharply above 4,000 m exactly when your body needs fuel.
4. Take the optional acclimatisation walks. An afternoon hour spent walking a few hundred metres higher and coming back down is genuinely useful.
5. Do not hide symptoms. Guides ask twice a day for a reason. Underreporting to avoid seeming weak is the most dangerous thing a climber does on this mountain.
6. Avoid alcohol and sleeping tablets. Both suppress the breathing drive that is doing the adaptation.

Does pre-acclimatising at home work?

Altitude tents and hypoxic training have some evidence behind them but require weeks of consistent use to produce a modest effect, and they are expensive. For almost everybody the same money is far better spent on an extra day or two on the mountain.

Genuinely spending time at altitude beforehand does help. If you have the opportunity to trek somewhere above 3,000 m in the weeks before, or to climb Mount Meru — which reaches 4,566 m and sits an hour away — that is real preparation rather than a proxy for it.

Sleep at altitude

Expect it to be poor, and do not treat that as a warning sign in itself. Many people experience a cycle where breathing gradually slows, pauses, and then restarts with a few deep breaths — often waking them. It is common above 3,000 m, it is not dangerous by itself, and it usually improves as you adapt.

Nobody sleeps well at Barafu. That is normal and it is why the itinerary before it matters.