At Uhuru Peak there is roughly half the oxygen available at sea level. Almost every climber feels it, most cope well, and a minority need to descend. Altitude — not fitness, not strength — is the main reason people do not summit Kilimanjaro.
The good news is that acclimatisation is largely a matter of strategy and habits, both of which you control.
What happens to your body
As air pressure falls, less oxygen crosses into your blood. Your body responds by breathing faster, raising your heart rate and, over days, producing more red blood cells. That adaptation needs time — which is exactly what an extra day on the mountain buys you.
Recognising the symptoms
| Condition | Typical symptoms | Action |
|---|---|---|
| Mild AMS (very common) | Headache, nausea, poor appetite, disturbed sleep, mild breathlessness | Slow down, hydrate, rest; usually settles overnight |
| Moderate–severe AMS | Persistent vomiting, headache not relieved by painkillers, severe fatigue | Stop ascending; descend if no improvement |
| HACE (brain) | Confusion, loss of coordination, unusual behaviour, drowsiness | Immediate descent — medical emergency |
| HAPE (lungs) | Breathlessness at rest, wet cough, chest tightness, blue lips | Immediate descent — medical emergency |
Our guides record your pulse, blood-oxygen saturation and a Lake Louise symptom score every morning and evening. Every climb carries bottled oxygen, a pulse oximeter and a full first-aid kit, and we are an AMREF Flying Doctors partner for evacuation. Guides are trained to act on the trend, not just a single reading.
Acclimatisation strategy
- Choose a longer itinerary — 7 or 8 days beats 6 every time
- Climb high, sleep low: the Lava Tower day on Lemosho and Machame exists for this reason
- Walk pole pole (slowly) — if you cannot hold a conversation, you are going too fast
- Drink 3–4 litres of water a day; dehydration mimics and worsens AMS
- Eat even when appetite disappears — your body needs the calories to adapt
- Skip alcohol and sleeping pills on the mountain; both suppress breathing
- Report symptoms honestly and early. Hiding a headache is how a minor problem becomes an evacuation
Diamox, in plain language
Acetazolamide (Diamox) speeds up acclimatisation by mildly acidifying the blood, which makes you breathe more. A common preventive dose is 125 mg twice daily starting a day before you gain serious altitude, but this is a prescription decision for your own doctor — discuss it before you fly. Expect tingling fingers, more frequent urination and a strange taste to fizzy drinks. Diamox is an aid, never a substitute for a sensible ascent profile.
Summit night
You leave Barafu or Kibo around midnight and climb six to seven hours to Stella Point in the dark and cold. This is the hardest part of any route. Eat something at the wake-up call, keep your water bottle upside down so it does not freeze at the valve, put your summit layers on inside the tent, and follow your guide's pace exactly. Most people who turn around here do so because they went too fast in the first hour.
The only correct response to HACE or HAPE symptoms is to lose altitude fast, and our guides have the final say. Going down 500–1,000 m resolves most cases quickly. A safe descent is a successful climb.
Frequently Asked Questions
How fit do I need to be?
Comfortable hiking 6–8 hours on consecutive days. Build up with long weekend walks, hills and stairs, ideally with a loaded daypack, for two to three months before you travel.
Does age matter?
Less than you would think. We have guided teenagers and climbers in their seventies. Acclimatisation time and pacing matter far more than age.
Is supplementary oxygen carried?
Yes — every departure carries bottled oxygen for emergency use. It is a descent aid, not a way to push on to the summit.
Planning This Trip?
Our Moshi team answers every enquiry personally. No deposit required at this step — we reply within 24 hours.
