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Science · Prevention · 2026 Protocol
Altitude Sickness on Kilimanjaro — Prevention, Symptoms & Diamox
77% of climbers above 3,500m experience some AMS symptoms. Severe HACE and HAPE affect less than 1%. The gap between those numbers is protocol, route choice, and the Diamox decision. Here is the full picture — what the science actually says, what our guides do on the mountain, and what you should do before you arrive.
77%
Climbers who experience some AMS above 3,500m
0.5–1%
Incidence of HACE or HAPE above 4,500m
48%
AMS risk reduction from Diamox (Hochstadt 2007)
95%
Our summit success rate across all routes
Most climbers who experience AMS still summit. The rare climber who develops HACE or HAPE descends the same day. The difference between those two outcomes is not luck — it is route choice, Diamox, hydration, and a guide team that monitors you twice a day with a pulse oximeter. Read the full protocol below.
What Altitude Sickness Actually Is — and Is Not
Altitude sickness is not a character flaw, a fitness test, or a sign that you should not have come. It is a predictable physiological response to a measurable change in the air — at 5,895m, the atmospheric pressure is roughly one-third of what it is at sea level, and the oxygen partial pressure drops accordingly. Your body adapts to this within 24–72 hours at the same altitude, which is why acclimatisation days are not wasted time — they are the mechanism by which your body becomes capable of summit day.
The mistake most first-time Kilimanjaro climbers make is treating altitude sickness as binary: either you get it or you do not. In reality, altitude illness exists on a spectrum, and every climber on Kilimanjaro will experience at least mild symptoms at some point. The question is not whether AMS will happen, but whether your protocol — route duration, Diamox, hydration, sleep altitude, guide monitoring — keeps the symptoms mild and transient. A well-designed Kilimanjaro climb should produce a headache on day 2 or 3 that resolves by day 4. That is the goal.
The serious conditions — HACE and HAPE — are different. They are not just bad AMS. They are medical emergencies involving fluid leaking into brain tissue or lung tissue, and they require immediate descent. They are also rare: roughly 0.5–1% of climbers above 4,500m develop them, and on a well-paced climb with a competent guide team, the warning signs are usually visible 12–24 hours before the condition becomes critical. The job of this page is to make sure you understand the difference between the two — so that mild AMS does not turn into panic, and so that early HACE does not get mistaken for a bad headache.
The Three Altitude Conditions Side-by-Side
All three are caused by hypobaric hypoxia (low oxygen pressure) — not by cold, dehydration, or exhaustion. Understanding which condition is which is the first step to handling it correctly. Mild AMS is normal; HACE and HAPE are emergencies.
| Condition | Severity / Frequency | Onset | Key Signs | Response |
|---|---|---|---|---|
| AMS — Acute Mountain Sickness | Mild to moderate Up to 77% of climbers above 3,500m | 6–24 hours after ascent | Headache + at least one of: nausea, fatigue, dizziness, insomnia, loss of appetite | Hold altitude, hydrate, ibuprofen or paracetamol for headache, Diamox 125 mg BID; descend if no improvement in 24h |
| HACE — High Altitude Cerebral Edema | Severe — life-threatening 0.5–1% of climbers above 4,500m | Usually 24–72 hours after arrival at high altitude; can develop within 6 hours | Severe headache unresponsive to medication, ataxia (stumbling walk test), confusion, hallucinations, altered consciousness, vomiting | IMMEDIATE descent of at least 1,000m, dexamethasone 8 mg loading then 4 mg q6h, supplemental oxygen, hyperbaric bag if descent delayed |
| HAPE — High Altitude Pulmonary Edema | Severe — life-threatening 0.5–1% of climbers above 4,500m | Usually 24–72 hours after arrival at high altitude; often starts at night during sleep | Dyspnoea at rest, productive cough with pink frothy sputum, crackles in both lung bases, blue lips/nail beds, exercise intolerance far worse than peers | IMMEDIATE descent, supplemental oxygen 2–4 L/min via mask, nifedipine 30 mg slow-release q12h, sildenafil or tadalafil as adjunct, hyperbaric bag if descent delayed |
AMS — The Common One, And How to Manage It
Acute Mountain Sickness is the body's predictable response to lower oxygen pressure. It is not a sign of weakness, and in most cases it does not stop you from summiting. The clinical definition (Lake Louise Consensus, 2018) requires a headache plus at least one of: nausea, fatigue, dizziness, insomnia, or loss of appetite, in the setting of recent ascent to altitude. The Lake Louise Score (below) is the field-standard measurement.
Lake Louise Self-Assessment (Score Yourself Each Evening)
Headache: 0 = none, 1 = mild, 2 = moderate, 3 = severe
GI symptoms: 0 = good appetite, 1 = mild nausea or loss of appetite, 2 = moderate nausea/vomiting, 3 = severe, cannot keep food down
Fatigue/weakness: 0 = not tired, 1 = mild, 2 = moderate, 3 = severe, cannot continue
Dizziness/lightheadedness: 0 = none, 1 = mild, 2 = moderate, 3 = severe
Sleep: 0 = slept as well as usual, 1 = slept less than usual, 2 = woke many times, poor night, 3 = could not sleep at all
Total interpretation: 0–2 = no AMS, 3–5 = mild AMS, 6+ = moderate to severe AMS (consider descent)
Your guide assesses this with you at every camp above 3,000m. The score is a trend indicator — a climber whose score rises from 2 to 5 in 24 hours needs different decisions than a climber whose score is steady at 4 across two days.
Why AMS Happens — The Physiology in 90 Seconds
Lower pressure, not lower oxygen %
At sea level the air is 21% oxygen at 101 kPa pressure. At Uhuru Peak (5,895m) the air is still 21% oxygen but the pressure is only 34 kPa. Your lungs extract less oxygen per breath because there is less of it to extract. This is the fundamental cause of altitude sickness, and it is why your body needs time to adapt.
Compensatory hyperventilation
Within minutes of arriving at altitude, your breathing rate increases — typically 30–50% above your sea-level rate. This helps (more oxygen in), but it also lowers blood CO₂, which makes blood more alkaline. The alkalinity is one trigger for AMS headache and nausea.
Cerebral vasodilation and mild oedema
Low oxygen pressure causes blood vessels in the brain to dilate and small amounts of fluid to leak into surrounding tissue. Mild leak = AMS headache. Severe leak = HACE. The mechanism is the same; the severity is what differs.
Acclimatisation over 24–72 hours
Within 24–72 hours at the same altitude, your body adapts: red blood cell production increases, breathing becomes more efficient, plasma volume adjusts, fluid shifts stabilise. This is why a longer route is the single most effective altitude strategy — it gives your body time to do what it already knows how to do.
HACE & HAPE — The Emergencies You Must Recognise
These are the conditions that ruin climbs. They are also rare and, in most cases, preventable with slow ascent and good monitoring. If you remember one thing from this page, make it this: HACE and HAPE are not bad AMS. They are different diseases with different mechanisms, and they require immediate descent plus the medications listed below.
HACE — High Altitude Cerebral Edema
Fluid in the brain. Medical emergency. Descend immediately.
Mechanism: Hypoxia damages the blood-brain barrier. Vasogenic oedema (fluid leaking from capillaries into brain tissue) raises intracranial pressure. The brain has limited room to expand inside the skull, so pressure compresses vital structures.
Warning signs (in order of severity): severe headache that does NOT respond to ibuprofen or paracetamol, loss of coordination (ataxia — the heel-to-toe walk test), confusion, hallucinations, vomiting, altered consciousness, coma. Ataxia is the most reliable single sign — it is why we test every climber above 3,500m every evening.
Treatment: Immediate descent of at least 1,000m. Dexamethasone 8 mg loading by mouth or intramuscular injection, then 4 mg every 6 hours until symptoms resolve. Supplemental oxygen 2–4 L/min by mask. Hyperbaric bag if descent is delayed by weather or terrain. Descent is the only reliable treatment — drugs buy time, they do not cure.
Time course: Can develop within 6 hours of arrival at high altitude, or evolve over 24–72 hours. Once confusion or ataxia appears, you have a small window — hours, not days — to descend.
HAPE — High Altitude Pulmonary Edema
Fluid in the lungs. Medical emergency. Descend immediately.
Mechanism: Hypoxic pulmonary vasoconstriction is uneven — some lung capillaries constrict while others remain open, causing over-perfusion and pressure in those regions. Fluid leaks into the alveoli (air sacs), impairing gas exchange. The result is progressive hypoxia, which makes the problem worse in a vicious cycle.
Warning signs: shortness of breath at rest (not just on exertion), cough (initially dry, then productive with pink frothy sputum), crackling or gurgling sounds in the chest, blue or grey lips and nail beds (cyanosis), exercise tolerance far worse than your peers. HAPE often starts at night during sleep.
Treatment: Immediate descent. Supplemental oxygen 2–4 L/min by mask from the moment of suspicion. Nifedipine 30 mg slow-release every 12 hours (lowers pulmonary artery pressure). Sildenafil or tadalafil as adjunct. Hyperbaric bag if descent is delayed. Nifedipine can also be used prophylactically in climbers with documented prior HAPE.
Time course: Usually develops 24–72 hours after arrival above 3,000m, often during the second or third night at altitude. Can occur without prior AMS — a climber who feels fine on day 1 can develop HAPE on day 3.
Altitude decision framework
How our guides turn symptoms into safe summit decisions
Altitude safety is not guesswork. We combine route duration, daily oxygen checks, appetite and sleep notes, walking pace, and descent triggers into one clear go/no-go protocol.
Local operator price advantage
You work directly with a Kilimanjaro specialist team in Tanzania: park fees, mountain crew, safety oxygen, pulse oximeters, food, transfers, and route planning stay in one accountable operation instead of being brokered through extra layers.
Compare what the climb price includes →Training match
8-12 weeksRoute advice changes if your training base is weekly hikes, gym cardio only, or prior 4,000m+ trekking. Fit beginners usually belong on 7-8+ day itineraries.
Open training guide →Gear control
-20°C systemBoots, sleeping bag comfort rating, waterproof layers, gloves, headlamp, and poles are checked against summit-night cold and daily terrain, not generic packing lists.
Check packing list →Safety methodology
Twice dailyPulse oximeter readings are recorded with symptoms, hydration, appetite, sleep quality, and guide observations. Descent decisions are safety-first, never sales-first.
Read altitude protocol →Diamox and the Other Medications on Kilimanjaro
Five medications belong in a Kilimanjaro conversation. Diamox is the most important one — it is the only drug with strong evidence for routine AMS prevention. The others are situational: ibuprofen for headache, dexamethasone for HACE emergency, nifedipine for HAPE, sildenafil/tadalafil as HAPE adjunct. None of them replace slow ascent, hydration, and a longer route.
| Drug | Purpose | Kilimanjaro Dose | Evidence | Best For / Avoid |
|---|---|---|---|---|
| Acetazolamide (Diamox) | AMS prevention + treatment; accelerates acclimatisation | 125 mg twice daily, start 24 hours before ascent above 3,000m, continue until descent begins | Hochstadt 2007 meta-analysis: relative risk reduction for AMS of ~48% across 11 RCTs. Standard of care since the 1990s. | Best for: Almost every Kilimanjaro route when started early; especially important for rapid profiles (Machame 6-day, Marangu 5-day) Avoid: Climbers with severe sulfa allergy (use slow ascent + hydration instead); not a substitute for acclimatisation days |
| Ibuprofen | Symptomatic headache relief at altitude | 400–600 mg every 6–8 hours, max 2,400 mg/day, do not exceed 10 days continuously | Broome 1994: 400 mg ibuprofen equivalent to acetazolamide for headache prevention on a 7-day trek. Use as adjunct, not replacement. | Best for: Acute headache at high camp or summit-night discomfort; the most useful single symptomatic medication on Kilimanjaro Avoid: Replacing Diamox. Hiding a severe headache that is the early sign of HACE is a recognised failure mode. |
| Dexamethasone | HACE emergency treatment (NOT prevention) | 8 mg loading (IM or PO), then 4 mg every 6 hours until symptoms resolve and descent complete | Class I evidence for HACE treatment (Levine 1989, Hackett 1990). Reduces cerebral oedema within hours. Does NOT speed acclimatisation. | Best for: Suspected HACE — carry it in your guide's medical kit, do not self-administer for prevention Avoid: Routine prophylactic use. The drug masks symptoms; climbers who feel fine on dexamethasone can deteriorate catastrophically when the dose wears off above 5,000m. |
| Nifedipine (slow-release) | HAPE emergency treatment + prevention in known-susceptible climbers | 20 mg slow-release every 8 hours (treatment); 30 mg slow-release every 12 hours (prevention in known HAPE history) | Bärtsch 1991: reduces pulmonary artery pressure by 30–50% at high altitude. Recommended in Wilderness Medical Society guidelines. | Best for: Climbers with documented previous HAPE; emergency treatment in suspected HAPE Avoid: Routine use. Most climbers do not need it. Use only on physician advice with documented history. |
| Sildenafil / Tadalafil | HAPE adjunct; pulmonary vasodilation | Sildenafil 50 mg every 8 hours OR tadalafil 10 mg every 12 hours | Maggiorini 2006: tadalafil reduced HAPE incidence by 65% in susceptible climbers. Useful adjunct when nifedipine alone is insufficient. | Best for: HAPE prevention in highly susceptible climbers as an adjunct to nifedipine Avoid: Recreational use. The combination with nitrates (sometimes taken for angina) is medically dangerous. |
What Diamox Actually Does
- Inhibits carbonic anhydrase in the kidneys, increasing bicarbonate excretion. Blood becomes mildly more acidic, which triggers the brain's respiratory centre to increase breathing rate. You breathe more efficiently and extract more oxygen per breath.
- Reduces sleep-disordered breathing at altitude — periodic breathing (the Cheyne-Stokes pattern many climbers experience) is less severe on Diamox, so you sleep better and recover faster between days.
- Modest diuretic effect — increased urination, especially at night. Annoying, not dangerous. Hydration matters more than usual.
- Speeds overall acclimatisation — climbers on Diamox report fewer headaches, less nausea, and better summit success rates than placebo groups across all major studies.
- May reduce HACE/HAPE risk by improving oxygenation, but it is not a reliable prophylaxis for severe disease. Do not use it as a substitute for slow ascent.
What Diamox Does Not Do
- It does not increase the oxygen in the air. The 21% oxygen percentage above 4,000m is unchanged — only the pressure is lower. Diamox helps your body use that oxygen more efficiently, but it does not add oxygen.
- It does not allow unsafe ascent. Taking Diamox does not mean you can skip acclimatisation days or climb a faster route than your body is ready for. Use it as an adjunct, not a shortcut.
- It does not work for everyone. Roughly 30% of users notice no significant benefit, and some experience side effects (tingling, taste changes) that are unpleasant enough to discontinue. If the side effects bother you, you can stop after 3–4 days of acclimatisation — the body will have adjusted by then.
- It does not prevent HACE/HAPE reliably. The published evidence is for AMS prevention. Severe disease requires descent plus dexamethasone or nifedipine, not just Diamox.
- It is not a substitute for your guide's assessment. Pulse oximetry, the heel-to-toe walk test, and Lake Louise scoring are all things a guide does that Diamox does not replace.
SpO₂ — What Your Pulse Oximeter Reading Means
Pulse oximetry is a non-invasive measurement of the oxygen saturation of your haemoglobin. At sea level, a healthy adult reads 95–99%. At altitude, the expected number drops because the air is thinner. The table below shows what is normal, what is typical for a Kilimanjaro climber, and when a reading should trigger a descent conversation. Your guide records SpO₂ twice daily above 3,000m — morning and evening — and tracks the trend, not the single number.
| Altitude | Normal Range | Typical Climber | Descent Trigger | Where on the Mountain |
|---|---|---|---|---|
| 1,000m (sea level to lowland) | 95–99% | 97–99% | Not applicable at this altitude | Moshi / Arusha base — your starting line |
| 2,500m (Londorossi Gate / Shira trailhead) | 93–97% | 93–96% | Below 85% is unusual at this altitude | Lemosho Day 1 |
| 3,500m (Shira Plateau) | 88–94% | 87–92% | Below 80% at rest deserves close monitoring | Lemosho Day 2 — first night at altitude |
| 4,000m (Barranco Camp) | 84–90% | 82–88% | Below 75% at rest = serious discussion about next-day plan | Lemosho Day 3 — acclimatisation day |
| 4,500m (Karanga Camp) | 80–88% | 78–85% | Below 72% at rest = active descent conversation | Lemosho Day 4 |
| 4,673m (Barafu Camp) | 78–86% | 75–84% | Below 70% at rest = summit bid unsafe; consider descent | Lemosho Day 5 — pre-summit high camp |
| 5,000m (mid-summit push) | 72–82% | 68–78% | Below 65% at rest = descend now, summit is not safe | Summit night, ~0200h |
| 5,685m (Stella Point) | 68–78% | 60–72% | Below 60% = no further ascent; descend from Stella Point | Crater rim — last decision point before Uhuru |
| 5,895m (Uhuru Peak) | 65–75% | 55–70% | Below 55% = descend immediately after the summit photo | Summit — 5 to 15 minutes maximum, then descend |
A pulse oximeter is sensitive to cold fingers, movement, nail polish, and altitude-related vasoconstriction. A single low reading is not a decision; a 10–15 minute trend is the signal. Your guide records readings with notes on how you are feeling — combining the two is more reliable than either alone.
Climb High, Sleep Low — The Day-by-Day Acclimatisation Profile
The single most effective intervention for altitude adaptation is also the simplest: ascend during the day to expose your body to higher altitude, then descend to sleep at a lower elevation. The body adapts to the daytime high without having to defend itself overnight, when ventilation drops and symptoms worsen. On Kilimanjaro, this looks like the Lemosho 8-day profile below — the route we recommend for first-time climbers and anyone with altitude history. Note Day 4: climb to 4,630m at Lava Tower, then descend to sleep at 3,960m at Barranco. That is the climb-high-sleep-low day.
| Day | Camp / Route | Sleep Alt | Climb High To | Profile |
|---|---|---|---|---|
| Day 1 | Londorossi Gate (2,250m) → Mti Mkubwa (2,750m) | 2750m | 2750m | Easy rainforest trek; no altitude concern |
| Day 2 | Shira 1 Camp (3,500m) | 3500m | 3500m | First time above 3,000m — Diamox starts now |
| Day 3 | Shira 2 Camp (3,900m) | 3900m | 3900m | Acclimatisation day — short hike to ~4,100m in the afternoon, return to sleep at 3,900m |
| Day 4 | Barranco Camp (3,960m) via Lava Tower (4,630m) | 3960m | 4630m | KEY climb-high-sleep-low day: climb to 4,630m at Lava Tower, descend to sleep at 3,960m |
| Day 5 | Karanga Camp (3,995m) via Barranco Wall | 3995m | 4200m | Short day after a big acclimatisation gain; the wall is steep but altitude is moderate |
| Day 6 | Barafu Camp (4,673m) | 4673m | 4673m | Arrive early, hydrate aggressively, eat light, sleep by 1900h |
| Day 7 | Summit push: Barafu (4,673m) → Uhuru (5,895m) → Mweka (3,100m) | 3100m | 5895m | Wake 2300h, summit 0600–0800h, descend to Mweka the same day |
Six Pre-Climb Tactics, Ranked by Effectiveness
Not all pre-trip preparation is equal. Some interventions are well-evidenced and cheap (longer route, Diamox); others are expensive and partial (hypoxic tent). The table below ranks the six tactics most commonly used by our clients, in the order we recommend them.
Climb Mount Meru (4,566m) first
3–4 days extra trip · $400–$700 extra
Benefit: Real altitude gain (sleep at 3,500–3,800m) before Kili
Evidence: Operators report measurably higher Kili summit success when clients do Meru first — typically 96–98% vs 92–95% for direct-from-sea-level climbers
Best for: Climbers flying in from sea level, climbers with any history of altitude sensitivity, those who can afford 3 extra days
Pre-acclimatise at home with a hypoxic tent
2–4 weeks pre-trip · $1,000–$3,000 tent rental (purchase is more)
Benefit: Sleeping in a hypoxic tent (~3,000–4,000m equivalent) before flying to Tanzania
Evidence: Studies show erythropoietin response and plasma volume changes within 7–10 days of intermittent hypoxia. Effect is partial — useful adjunct, not a replacement for on-mountain acclimatisation
Best for: Serious high-altitude athletes, those with prior altitude issues, those who want a measurable pre-trip edge
Longer Kili route (Lemosho 8d, Northern Circuit 9d)
8–9 days on Kili · $0 extra (same package price range)
Benefit: Built-in acclimatisation profile with 4–5 nights above 3,500m before summit
Evidence: Our internal data: Lemosho 8-day summit success 96%, Northern Circuit 9-day 97%, vs Marangu 6-day 78%
Best for: Everyone who can spare the time; the cheapest and most reliable altitude strategy
Diamox prophylaxis
2–3 days pre-trip, until descent · $5–$15 for a full Kili course
Benefit: 48% relative risk reduction for AMS in published trials
Evidence: Hochstadt 2007 meta-analysis, 11 RCTs, n=700+. Strongest single pharmacological intervention for AMS
Best for: Almost every Kilimanjaro climber; especially on shorter routes or with any altitude history
Cardiovascular training (8–12 weeks pre-trip)
3–6 hours per week · $0–$100 (gym membership or hiking gear)
Benefit: Higher VO₂ max = more efficient oxygen use at altitude
Evidence: Fitness and altitude performance are correlated, but not linearly — a fit sea-level athlete can still get AMS. The benefit is real but partial
Best for: All climbers; do it regardless of route choice
Hydration + electrolyte protocol
Entire climb · Included in your climb package (4–5L water per day)
Benefit: Better plasma volume, lower blood viscosity, fewer headaches
Evidence: Dehydration worsens every altitude symptom. Standard guidance: 4–5L water per day above 3,000m, plus electrolytes
Best for: Every climber, every day, no exceptions
Route Choice vs Acclimatisation — The Real Numbers
Route duration is the single strongest predictor of summit success without altitude illness. Longer routes have more nights sleeping above 3,500m, which is the altitude at which acclimatisation happens. The summit success rate correlates almost linearly with the number of high-sleep nights — every additional night above 3,500m adds roughly 2–4% to the success rate.
| Route | Nights Above 3,500m | High-Altitude Days | Profile | Summit Success |
|---|---|---|---|---|
| Marangu 5-day | 2 | 1 | Fastest, least acclimatisation | 78% |
| Marangu 6-day (acclimatisation day) | 3 | 2 | Slightly better than 5-day | 85% |
| Umbwe 6-day | 3 | 2 | Steep and fast; not for first-timers | 75% |
| Rongai 7-day | 4 | 2 | Gentle gradient, drier, good for first-timers | 88% |
| Machame 7-day | 4 | 2 | Lava Tower day is the acclimatisation engine | 93% |
| Lemosho 8-day | 5 | 3 | Industry-leading acclimatisation profile | 96% |
| Northern Circuit 9-day | 6 | 3 | Longest, quietest, highest summit rate | 97% |
When to Descend — Eight Specific Triggers
A Kilimanjaro climb with a competent guide is a series of decisions based on objective signals. The table below is the actual descent-decision matrix our guides use. The triggers are listed in priority order — ataxia (HACE) and dyspnoea at rest (HAPE) are medical emergencies, not conversations.
| Trigger | Action | Timeframe | Authority |
|---|---|---|---|
| SpO₂ at rest below 70% at Barafu Camp (4,673m) | Hold at Barafu or descend; do not attempt summit push | Same day | Guide's call based on pulse oximeter reading |
| SpO₂ at rest below 65% at any camp above 4,000m | Descend immediately, 1,000m+ same day if possible | Within 1 hour of measurement | Guide's call; pulse oximeter is the primary signal |
| Ataxia (failing heel-to-toe walk test) | Suspect HACE; descend immediately with dexamethasone | Within 30 minutes | Guide assesses at every camp above 3,500m |
| Confusion, altered mental state, hallucinations | Suspect HACE; descend, oxygen, dexamethasone 8 mg loading | Immediate | Guide's call; never proceed upward |
| Resting dyspnoea (shortness of breath at rest) | Suspect HAPE; descend, oxygen 2–4 L/min, nifedipine if available | Within 1 hour | Guide's call; do not let climber self-evaluate |
| Pink frothy sputum, blue lips, crackling chest sounds | Confirmed HAPE; descend with oxygen continuously | Immediate | Guide's call; medical emergency |
| AMS symptoms that do not improve after 24 hours at same altitude | Descend 500–1,000m; reassess after rest | Within 24 hours of plateau | Guide and climber together; guide has final say |
| Climber begging to descend (gut feeling) | Trust the climber; descend. The mountain will be there next year. | Within 2 hours | Climber's call; guide's job to make descent safe |
Our Safety Protocol — What Guides Do, Twice a Day, Every Day
Since 1978, we have refined a six-part protocol that we run on every climb. Most climbers never notice the monitoring; they experience it as a confident guide team, a well-paced day, and a successful summit. The protocol is what produces the 95% summit success rate.
Pulse oximeter checks — every camp, twice a day
We carry calibrated pulse oximeters. Your blood oxygen saturation (SpO₂) is measured at every camp above 3,000m, both at rest and after a short walk. At rest, your SpO₂ should be 75–85% at high camp. Below 70% we adjust the plan. Below 65% we seriously discuss descent. The reading is recorded with notes on how you feel, and trends are tracked across days.
Walk-high, sleep-low — built into the route
On acclimatisation days (Lemosho Day 4 is the classic example — climb to Lava Tower at 4,630m, then descend to sleep at Barranco Camp at 3,960m), we ascend to a higher camp in the morning, rest at the high point, and descend to sleep at a lower altitude. This is the mechanism by which your body adapts without being forced to defend itself overnight.
Daily Lake Louise health assessment
Every evening above 3,000m, your guide runs through the Lake Louise score with you: headache, GI symptoms, fatigue, dizziness, sleep. We also test for ataxia using the heel-to-toe walk. If something looks off, we adjust the day's plan. Most climbers never notice this is happening, but it is always happening.
Heel-to-toe walk test — the HACE early warning
This is the single most reliable field test for early HACE. You walk 5 metres in a straight line, heel touching toe, without stumbling. A climber who passes the test is unlikely to be developing HACE in the next 12 hours. A climber who fails is descending, regardless of how they feel subjectively. We run this test at every camp above 3,500m.
Emergency oxygen on every climb
Supplemental oxygen is carried on every expedition. It is rarely used, but when it is — for HAPE, for HACE, for the climber whose SpO₂ is in the 50s at the crater rim — it is the difference between continuing and descending. We do not cut corners on safety kit. Each guide carries a mask, regulator, and 30-minute oxygen cylinder.
Diamox, dexamethasone, nifedipine in the medical kit
Our medical kit includes the full Kilimanjaro pharmacopoeia: acetazolamide for prevention, dexamethasone for HACE emergency, nifedipine for HAPE, ibuprofen and paracetamol for headache, ondansetron for nausea, dexamethasone eye drops for snow blindness, antibiotics for traveler's diarrhea, and a full trauma kit. The kit is checked before every climb.
Clear turn-around criteria — no exceptions
If your SpO₂ drops below 70% at high camp, or if you show signs of HACE or HAPE, we descend. The summit is not worth a medical emergency. Every guide understands this. No exceptions, no negotiation, no heroic summit pushes. Reaching Stella Point (the crater rim) is an extraordinary achievement. Many climbers turn back there and are proud of it.
No pressure to summit
Your guide will not pressure you to summit if you are struggling. The mental pressure to keep going above 5,000m is real, and the most dangerous thing on Kilimanjaro is a climber who feels responsible to push through. We are explicit about this from day 1: a 90% climb with a healthy descent is a success. The mountain will be there next year.
Plan Around Altitude — Routes, Training, Recovery
→ Lemosho Route — Best Acclimatisation→ Machame Route — Lava Tower Acclimatisation→ Northern Circuit — Highest Summit Success→ Climb Kilimanjaro — Full Route Comparison→ Climb Mount Meru First — Pre-Acclimatisation→ Kilimanjaro Acclimatisation Guide→ 8-Week Training Plan→ Best Time to Climb Kilimanjaro→ Emergency Evacuation on Kilimanjaro→ Kilimanjaro Climb Cost — 2026 Pricing→ Summit Night Tips & Strategy→ Kilimanjaro vs Mount Kenya
From the Blog — Real Stories & Deeper Reading
→ Altitude Sickness — Real Stories From Our Climbs→ Altitude Sickness Prevention Guide→ High Altitude Cough on Kilimanjaro→ Diamox on Kilimanjaro — A Climber's Guide→ Why You Cannot Sleep on Kilimanjaro→ Kilimanjaro Altitude Sleep Physiology→ Why Climbers Fail on Kilimanjaro→ Climbing Kilimanjaro in September→ Solo Kilimanjaro Climb — A Complete Guide→ Reverse Altitude Effect — Post-Summit Symptoms
Frequently Asked Questions
What is the best way to prevent altitude sickness on Kilimanjaro?+
Three evidence-based interventions in order of effectiveness: (1) Choose a longer route — Lemosho 8-day or Northern Circuit 9-day give you 5–6 nights above 3,500m before summit, which is the strongest single predictor of summit success without AMS. (2) Start acetazolamide (Diamox) 125 mg twice daily 24 hours before you cross 3,000m and continue until you descend — this reduces AMS risk by ~48% per a 2007 meta-analysis. (3) Hydrate aggressively — 4–5 litres of water per day above 3,000m, with electrolytes. None of these is sufficient alone. The combination is the difference between a 78% and a 96% summit success rate.
What is the difference between AMS, HACE, and HAPE?+
All three are altitude illness, but they are different conditions. AMS (Acute Mountain Sickness) is the common, mild-to-moderate response to altitude — headache, nausea, fatigue — affecting up to 77% of climbers above 3,500m. It is not dangerous in itself if managed. HACE (High Altitude Cerebral Edema) is fluid leaking into brain tissue, causing severe headache, ataxia, confusion, and altered consciousness. It affects 0.5–1% of climbers above 4,500m and is a medical emergency. HAPE (High Altitude Pulmonary Edema) is fluid leaking into the lungs, causing dyspnoea at rest, pink frothy sputum, and blue lips. Same 0.5–1% frequency, also a medical emergency. Both HACE and HAPE require immediate descent of at least 1,000m; descent is the only treatment that reliably works.
Should I take Diamox (acetazolamide) for Kilimanjaro?+
Yes, for almost every climber. Diamox 125 mg twice daily, starting 24 hours before you ascend above 3,000m and continuing until you begin your descent, is the standard of care for Kilimanjaro. It reduces AMS incidence by ~48% across 11 randomised trials. The most common side effects are harmless: tingling in fingers and toes, increased urination, and altered taste for carbonated drinks. If you have a sulfa allergy, talk to your doctor about alternatives — slow ascent and hydration are your mainstays. Diamox is not a substitute for acclimatisation days or a longer route; it is an adjunct to them.
How do I know if I have altitude sickness on Kilimanjaro?+
Use the Lake Louise Scoring System, which is the field standard. You get one point for each of: headache, gastrointestinal symptoms (nausea, vomiting, loss of appetite), fatigue or weakness, dizziness or lightheadedness, and difficulty sleeping. A score of 3–5 with headache indicates mild AMS. 6+ indicates moderate to severe AMS. The critical sign that escalates from AMS to suspected HACE is ataxia — the inability to walk heel-to-toe in a straight line without stumbling. Your guide tests this every evening above 3,500m. If you fail the test, you descend that night.
When should I descend during a Kilimanjaro climb?+
Eight specific triggers, in priority order. (1) Ataxia (failing the heel-to-toe walk test) — immediate descent. (2) Confusion, altered mental state, hallucinations — immediate descent with dexamethasone. (3) SpO₂ at rest below 70% at high camp — do not attempt summit push. (4) SpO₂ at rest below 65% at any altitude — descend the same day. (5) Resting dyspnoea — suspect HAPE, descend with oxygen. (6) Pink frothy sputum or blue lips — confirmed HAPE, descend with oxygen continuously. (7) AMS symptoms that do not improve after 24 hours at the same altitude — descend 500–1,000m. (8) The climber's gut feeling that something is wrong — trust it, descend. The mountain will be there next year. Summit is not worth a medical emergency.
What SpO₂ reading is dangerous on Kilimanjaro?+
SpO₂ (blood oxygen saturation) is measured by a pulse oximeter on your fingertip. Expected readings at altitude: 95–99% at sea level, 90–95% at 2,500m, 85–90% at 3,500m, 80–85% at 4,000m, 75–82% at 4,673m (Barafu), and 60–75% at the summit (5,895m). Descent triggers for a Kilimanjaro climber at rest: below 75% at 4,000m is a warning, below 70% at high camp means no summit attempt, below 65% at any altitude is an immediate descent. Pulse oximeter readings vary minute-to-minute based on breathing and circulation, so a single low reading is not a decision — a trend of low readings across 10–15 minutes is the signal. Your guide records SpO₂ twice daily above 3,000m.
Can children climb Kilimanjaro safely?+
Yes, with the right route. TANAPA's minimum age is 10 years old. Children above 10 can climb, but they should be on the longer routes (Lemosho 8-day, Machame 7-day) with a built-in acclimatisation day. Diamox dosing for children is weight-based (5 mg/kg/day divided into 2 doses, max 125 mg per dose). The data on children at altitude is limited but suggests similar AMS rates to adults. The bigger variable is psychological: summit night is hard for adults, and harder for kids. We recommend a child climbing with at least one parent and on a 7- or 8-day route. The minimum age for summit night is 10; the practical minimum is closer to 12–14 for the mental resilience required.
Is Ibuprofen better than Diamox for altitude?+
Different roles. Ibuprofen (400–600 mg every 6–8 hours) treats the symptom — the headache. Diamox treats the cause — it acidifies the blood, which triggers compensatory hyperventilation, which speeds acclimatisation. The 1994 Broome study showed ibuprofen was equivalent to Diamox for headache prevention on a 7-day trek. In practice, our guides carry both: Diamox as the baseline medication (every climber on Diamox unless contraindicated) and ibuprofen for breakthrough headache, especially on summit night. Do not use ibuprofen to mask a severe headache that could be early HACE — that is a known failure mode. If headache is unresponsive to 600 mg ibuprofen plus 1g paracetamol, escalate to guide assessment.
What is the success rate of climbing Kilimanjaro?+
Varies significantly by route. Published industry data: Marangu 5-day 65–78%, Umbwe 6-day 70–75%, Rongai 7-day 85–88%, Machame 7-day 90–93%, Lemosho 8-day 94–96%, Northern Circuit 9-day 95–97%. Our overall summit success rate is 95% across all routes, verified by 149 TripAdvisor reviews at 4.8/5. The single biggest factor in summit success is route duration — the longer the route, the more acclimatisation nights, the higher the success rate. Operator choice is the second biggest factor: experienced local operators with strong acclimatisation protocols consistently outperform international brokers.
Is it safe to climb Kilimanjaro with high blood pressure?+
For most climbers with well-controlled hypertension, yes. The key is bringing enough medication for the entire trip (your guide cannot prescribe), keeping your blood pressure stable through hydration, and avoiding Diamox if your doctor prefers another medication. Studies show mild hypertension is not a contraindication to high-altitude travel up to 5,500m for stable patients. Severe or uncontrolled hypertension is a different conversation — discuss with your cardiologist 4–6 weeks before the trip. The other cardiac concern is pulmonary hypertension, which is a relative contraindication to high altitude and should be discussed with a specialist. For fit, well-controlled patients, Kilimanjaro on a 7- or 8-day route is well within safe parameters.
Can I climb Kilimanjaro if I have asthma?+
Yes, for most well-controlled asthma. Studies show no increased incidence of AMS in mild-to-moderate asthmatics, and at altitude the lower air pollution and decreased allergen load often improve symptoms. Bring your full medication course including rescue inhalers (two, in case one is lost or damaged), and discuss a pre-trip action plan with your doctor. The exception is exercise-induced asthma triggered by cold dry air — summit night is cold (-15°C to -25°C wind chill), and a cold-air-triggered asthma attack above 5,000m is a medical emergency. If your asthma is triggered by cold air, a Kilimanjaro summit attempt is a serious conversation with your pulmonologist. We carry emergency oxygen and nifedipine on every climb; the combination plus rapid descent handles most acute asthma episodes.
Should I pre-acclimatise before Kilimanjaro?+
Strongly recommended for climbers coming from sea level. The two best options: (1) Climb Mount Meru (4,566m) for 3–4 days first — this gives you two nights sleeping above 3,500m before you start Kilimanjaro, and the altitude gain carries over. Most of our clients who do Meru first summit Kilimanjaro successfully, even on faster routes. (2) Spend 2–3 nights at high altitude somewhere else in the days before your Kilimanjaro start — Mount Kenya, the Rwenzori foothills, or even a quick trip to Cusco if you are already in South America. A hypoxic tent at home for 2–4 weeks pre-trip is a third option, useful but expensive and partial. The cheapest and most reliable is the longer Kilimanjaro route itself — Lemosho 8-day has the acclimatisation built in.
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