Altitude is the one part of a Kilimanjaro climb that no operator controls. It is not decided by how many hours you spent in the gym before you flew out, and it is not decided by age. It is decided mostly by how fast you go up, and by how your particular body reacts to roughly half the oxygen available at sea level, which is what is on offer at Uhuru Peak, 5,895 metres above it.
This piece sets out what altitude sickness actually is, what a route can do to reduce your risk of it, and what a good guide checks for every evening on the mountain. It also says what it will not say: a summit success rate. Nobody can promise you the top, and any operator who quotes a precise figure is telling you more about their marketing than about your own chances.
The short answer
Altitude sickness on Kilimanjaro is caused by how fast you ascend, not by how fit you are. It can affect anyone, at any age, at any fitness level, above about 3,000 metres. The best protection is a longer route built around a climb-high, sleep-low day, and a guide who checks your oxygen saturation every evening.
Fitness: not the variable that decides the summit
Altitude sickness, properly called acute mountain sickness, is caused by ascending faster than the body can adjust to falling air pressure and the falling amount of oxygen that comes with it. It has nothing to do with how strong your legs are. A marathon runner and someone who has not jogged in a decade can walk into the same evening health check at Barafu Camp, 4,673 metres, and get the same result, because what is being measured there is not fitness — it is how quickly that particular body is adjusting to the height it is at.
If anything, fitness can work against a climber in the first few days. A strong walker moves fast, reaches camp early, and has energy left to explore the ridge above it before dinner — all of which adds height the body has not asked for. The climbers who do best are often the ones who walk at the pace their guide sets rather than the pace their legs want, because on
Kilimanjaro the climb is won on the evenings spent sitting still at altitude, not the mornings spent covering ground quickly.
What actually predicts a good outcome is unglamorous: how many nights are spent above 3,000 metres before summit night, how gradually the sleeping altitude rises from one camp to the next, and whether a day is built in purely to climb high and sleep low. None of that shows up on a fitness test. It shows up in the itinerary, which is the one part of the climb you choose before you ever see the mountain — and the reason route choice matters more than any training plan.
Sleeping altitude, night by night| Night | Machame — 8 days | Lemosho — 9 days |
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| 1 | Moshi, about 890 m | Moshi, about 890 m |
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| 2 | Machame Camp, 3,010 m | Mti Mkubwa, 2,750 m |
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| 3 | Shira Camp, 3,840 m | Shira 1, 3,500 m |
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| 4 | Barranco, 3,960 m (via the Lava Tower) | Shira 2, 3,850 m |
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| 5 | Karanga, 3,995 m | Barranco, 3,960 m (via the Lava Tower) |
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| 6 | Barafu, 4,673 m — summit night | Karanga, 3,995 m |
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| 7 | Mweka, 3,100 m, after the summit | Barafu, 4,673 m — summit night |
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| 8 | — | Mweka, 3,100 m, after the summit |
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Route length: how it changes your acclimatisation
Every Kilimanjaro route climbs to the same summit, Uhuru Peak at 5,895 metres, but they do not spend the same number of nights getting there, and that is the single biggest difference between them. A shorter route reaches altitude faster and gives the body less time to adjust; a longer one spreads the same climbing over more evenings and more sleep at height. See
how the routes compare for the full picture — this section is about what the extra nights actually buy you.
The
eight-day Machame route builds in one deliberate climb-high, sleep-low day: up to the Lava Tower at 4,630 metres for lunch, then down to sleep at Barranco, 3,960 metres, a net gain of only 120 metres despite the 790 climbed. The
nine-day Lemosho route does something similar earlier, with two nights on the Shira plateau at 3,500 and 3,850 metres before it reaches the same Lava Tower day. Neither can promise a summit; both are built around the same principle, that height gained slowly is height the body can use.
The shortest itineraries skip this. A route walked with no day built to climb high and sleep low asks the body to do in five or six nights what other itineraries spread over seven or eight. That is not to say the shorter versions are unsafe in themselves — the park permits them — only that they leave far less room for a body that is adjusting slowly, and slow adjustment is normal, not a sign of unfitness.
Altitude sickness: the Lake Louise score, explained
The standard way of recognising altitude sickness on a mountain is the Lake Louise score, and it is simple enough that a guide can run through it at every evening health check. A headache, plus at least one of nausea or loss of appetite, unusual fatigue, dizziness, or trouble sleeping, adds up to mild acute mountain sickness. It is common above 3,000 metres, uncomfortable, and usually not dangerous provided it is not ignored.
What is dangerous is a small set of signs that mean the altitude is affecting the brain or the lungs rather than just causing discomfort: a climber who cannot walk in a straight line heel to toe, confusion or unusual behaviour, breathlessness at rest rather than on exertion, or a cough that brings up frothy or blood-tinged fluid. Any one of those is a reason to descend immediately, at night, without waiting for morning.
This is why a pulse oximeter — a small clip worn on a fingertip that reads blood oxygen saturation and pulse — is standard kit on the mountain, and why a good guide takes a reading every evening rather than once. A single number means little on its own; what matters is the trend from one night to the next, read alongside how the climber is actually walking, eating and sleeping, not just what the screen shows.
Turnaround calls: what a good guide checks
Ask any operator, before you book, who makes the call to turn a climber round, and on what evidence. The honest answer is that it should be the guide standing next to you at altitude, not a manager in an office, and it should rest on the evening checks — the oxygen reading, the Lake Louise questions, and simply how you look and sound — rather than on how much you have paid or how disappointed you will be.
Ask, too, what happens next if you are turned round. A properly staffed climb carries enough guides that one can descend with a single climber while the rest continue under the lead guide, which matters whether you are climbing privately or on a
joining departure with people you met a week ago. If the answer is that the whole group would have to turn back together, that is worth knowing before summit night, not during it.
None of this changes with the season. A full-moon date in a dry month does not lower anyone’s risk of acute mountain sickness, and a wet month does not raise it — see
when to climb Kilimanjaro, month by month for what the calendar does and does not decide. A guide who turns a climber round at Stella Point, 5,756 metres, rather than pushing on to Uhuru Peak, has made the climb safer, not failed it.
Oxygen and kit: what to ask before you book
Ask whether the crew carries emergency oxygen and a portable hyperbaric bag, sometimes called a Gamow bag, and what each is actually for. Both exist to get a sick climber down safely, buying time on the descent, not to get a struggling climber up. The only real treatment for acute mountain sickness and its dangerous forms is descent, and any operator suggesting otherwise — pushing on with oxygen rather than turning round — is not describing standard practice.
Ask about the guide-to-climber ratio, because it is what makes a safe turnaround possible in practice and not just in policy: one guide cannot walk a sick climber down and keep leading the rest of the party at the same time. Ask, separately, whether your travel insurance explicitly covers trekking to 6,000 metres — many standard policies stop at 3,000 or 4,000, and the gap only becomes visible when a claim is refused.
What a route or an operator cannot do is guarantee the summit, and none of the questions above change that. What they can do is give a body more time to adjust, and give a guide the means to act on what that body is telling them. If you are weighing routes with exactly this in mind,
find a journey filters our own climbs by length and season.
Questions people ask
What causes altitude sickness on Kilimanjaro?
Altitude sickness is caused by ascending faster than the body can adjust to falling oxygen levels, not by lack of fitness. It can affect very fit climbers and unfit ones alike, at any age. What reduces it is a slower rate of ascent, more nights spent above 3,000 metres, and a route that includes a day built to climb high and sleep low.
Does being fit help you summit Kilimanjaro?
Fitness makes the walking easier and more enjoyable, but it does not protect against acute mountain sickness, which is caused by the rate of ascent rather than physical condition. Fit climbers sometimes move faster than their body is adjusting and arrive at camp having gained more height than is useful. Walking at the guide’s pace matters more than gym fitness.
What does altitude sickness feel like on Kilimanjaro?
Mild acute mountain sickness is a headache plus nausea, loss of appetite, unusual tiredness, dizziness or difficulty sleeping — the Lake Louise score most guides use. It is common above 3,000 metres and usually settles with rest. Danger signs are different: loss of coordination, confusion, breathlessness at rest, or a cough with frothy fluid, which mean descend immediately.
What is the Lake Louise score?
It is the standard scoring system for recognising acute mountain sickness: a headache plus at least one of nausea, fatigue, dizziness or poor sleep. Guides on Kilimanjaro use a version of it at evening health checks, alongside a pulse oximeter reading, to track how a climber is coping with altitude from one night to the next.
Why do guides use a pulse oximeter on Kilimanjaro?
A pulse oximeter measures blood oxygen saturation and pulse from a clip on the fingertip. One reading on its own says little; what matters is the trend across several evenings, read together with the Lake Louise symptoms and how a climber is actually walking and eating. Good operators record it every night from the first camp onward.
Can altitude sickness be fatal on Kilimanjaro?
In its severe forms — fluid on the brain or the lungs, known as HACE and HAPE — it can be. Both are rare when guides act early on warning signs, and both are treated by immediate descent. This is why a properly staffed climb carries enough guides for one to take a sick climber down while the rest continue.
Which Kilimanjaro route has the best acclimatisation?
Routes with more nights above 3,000 metres and a built-in climb-high, sleep-low day generally give the body more time to adjust, which is why longer itineraries tend to summit more often than the shortest ones. See our route-by-route comparison for how Machame, Lemosho and the others differ, night by night.
What should I ask an operator about their turnaround policy?
Ask who decides to turn a climber round, and on what evidence — it should be the guide on the mountain, using oxygen readings and symptoms, not a fixed rule applied from an office. Ask what happens next: whether an assistant guide can descend with one climber while the rest continue, and whether that holds on both private and joining departures.
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Last updated 13 September 2026
