On Aconcagua, altitude is the main objective risk factor. The Normal Route may not call for difficult climbing, but the summit stands at 6962 m, and between Mendoza, base camp and the high camps the body covers a large altitude range in a limited time.
This article explains general principles and is not a substitute for medical advice. Medication, contraindications and individual prophylaxis should be discussed with a specialist in altitude medicine before the trip, while decisions on the route are taken according to how a climber is actually doing.
What acclimatisation is
Acclimatisation is the body’s adaptation to a reduced supply of oxygen. It takes time and does not come from being fit. The rate of height gain, the altitude you sleep at, your previous response to altitude and any recent acclimatisation all matter more than your speed at sea level.
Aconcagua programmes use a gradual approach, extra nights, day walks above the camp and a return lower down to rest. The «climb high, sleep low» pattern gives you the stimulus of altitude without immediately moving your overnight camp to the highest point reached.
What a longer programme gives a first-timer
More days do not guarantee the summit and do not rule out illness. What they give you is something else: the ability to raise your sleeping altitude more slowly, to observe how your body responds and to use the reserve when the weather or your adaptation is poor.
The 17-day programme works as the main format for someone without fresh pre-acclimatisation. The 12-day programme demands a stronger starting position. The 7-day Blitz is designed for someone who arrives already acclimatised from another mountain.
Early symptoms must not be concealed
Headache, unusual weakness, nausea, loss of appetite, disturbed sleep and generally feeling worse after gaining height all need attention. A single symptom does not always mean a serious condition, but how it develops matters more than any wish to keep to the schedule.
Tell your guide about any change immediately. Concealed symptoms deprive the team of the chance to slow down in time, stop gaining height or descend.
Warning signs
Loss of coordination, confusion, marked breathlessness at rest, a sharp fall in performance, a cough with worsening breathing and rapidly progressing symptoms all call for an immediate assessment of the situation and action by the team. Where severe altitude illness is suspected, continuing upward is not an option.
Descent remains the key way of removing the effect of altitude. Which way, how urgently, with whom, and whether evacuation is needed are decided by the guides and medical professionals according to the situation.
What helps reduce the risk
- a realistic schedule and a gradual increase in sleeping altitude
- a calm pace with no racing between climbers
- enough rest, drinking and regular meals
- refusing to keep gaining height when things get worse
- honest information about previous reactions and illnesses
- contingency days and a willingness to change the programme
Official medical guidance on the general principles of altitude is published by the CDC Yellow Book. It also stresses gradual height gain and the rule that you do not go up with worsening symptoms.
A pulse oximeter does not make a diagnosis
Blood oxygen saturation readings can be a useful part of monitoring, but they depend on altitude, the temperature of your hands, the quality of the device and the measuring technique. A single number is no substitute for assessing symptoms, behaviour, coordination and the overall trend.
The profile of the 17-day programme
On the classic schedule, altitude rises in steps: Confluencia at 3300 m, a day walk to Plaza de Francia at 4200 m, Plaza de Mulas at 4350 m, Plaza Canadá at 5000 m, Nido de Cóndores at 5600 m and Cólera at 6000 m. The first push to the high camps ends with a descent to base camp to recover, after which the team goes up again.
| Element | Why it is there |
|---|---|
| Gradual overnight stops | To give the body time to adapt |
| A day walk higher | To take the load and come back down |
| Descent to base camp | To recover before the decisive cycle |
| A second ascent | To test altitude tolerance after a rest |
| Contingency days | To keep flexibility, not to promise a summit |
What to tell your guide every day
- The quality of your sleep and how often you woke.
- Any headache and how it has changed.
- Appetite, nausea and whether you can drink.
- Unusual breathlessness at rest, or a cough.
- Any loss of coordination, attention or change in behaviour.
- A sudden drop in performance at the same pace as before.
This is not a guide to treating yourself. Symptoms at altitude are assessed as a trend, and the decision may involve stopping the ascent, resting, descending or evacuating. Concealing your condition for the sake of the summit is dangerous both for you and for the team.
Why being fit does not protect you from altitude
A strong athlete can move faster and thereby overload the body sooner. Aerobic training helps you do the work, but it does not guarantee a normal response to thin air. On the route, what counts is a slow pace, a consistent sequence of overnight camps, recovery and honest observation of symptoms.
The short programme and pre-acclimatisation
The 7-day programme requires recent pre-acclimatisation: the minimum considered is an altitude of 5000 m, preferably 5500 m. The decision is based not only on the summit reached but on the altitude of the overnight camps, how you felt and the interval between routes.
The 7-day Blitz does not build acclimatisation from scratch. You have to arrive with a recent altitude profile that matches the point at which you join the route. The 12-day programme is also tighter than the classic one. An old ascent confirms experience, but not current adaptation.
Compare the 17-day schedule, the comparison of the three programmes, the purpose of each camp and the reasons people turn back on Aconcagua.
Questions about acclimatisation
Can you acclimatise at home in advance?
Ordinary training improves your fitness but does not reproduce a full profile of nights at altitude. Specialist methods should be discussed with a competent doctor and with the operator, and never treated as an automatic replacement for the route itself.
Does a recent climb of another peak help?
It can, provided the altitudes slept at, the duration and the interval between expeditions are known. Accumulated fatigue is taken into account at the same time. A pair of routes has to be planned as a single load.
Can a decision be based on a device reading alone?
A single reading, without symptoms, a trend and the guide’s assessment, does not describe the whole situation. You should not diagnose yourself, nor conceal how you feel because of a «good number».
Practical preparation is described in a separate plan, and what happens on summit day in our analysis of the push from Cólera.
The five phases of acclimatisation on Aconcagua
| Phase | Task | What is assessed |
|---|---|---|
| Mendoza and entering the park | Start the route with no critical gaps | Health, documents, kit and recovery after the flight |
| Confluencia | Settle into a calm rhythm | Sleep, appetite, drinking and the response to the first altitude |
| Plaza de Mulas | Recover before the pushes above base camp | How your condition is trending and whether you can carry a load |
| High-altitude cycles | Test nights at around 5000-6000 m | Performance today and recovery tomorrow |
| The summit attempt | Use your adaptation without spending the reserve you need for the descent | Pace, coordination, weather and the state of the whole group |
Success in each phase is not the same as the highest point reached. On the approach the aim is not to exhaust yourself; in the first cycle it is to gather information and come back down; in the high camp it is to keep the ability to set off and descend safely.
How to put together an altitude history
A list of summits without dates and overnight altitudes is not enough. To choose a programme, provide your recent routes, your maximum daytime altitude, the altitudes you slept at, the number of days, your symptoms, any medication, the reason you turned back and how you were after returning.
| Information | Why it matters | A weak answer |
|---|---|---|
| The date of the route | Acclimatisation fades over time | «A few years ago» |
| Sleeping altitude | Sleeping is different from a brief visit | The summit altitude only |
| The sequence of days | Shows repeated work without full rest | One good day |
| Symptoms and decisions | Reveals recurring risk | «Everything was fine» |
| Recovery | Especially important before back-to-back expeditions | Judging by the summit alone |
Turning back because of weather can reflect well on your experience. A summit reached amid a serious deterioration, by contrast, calls for a cautious next step. The history helps choose a format; it is not a measure of heroism.
A day walk and a night at altitude
Going briefly higher is usually easier than spending the night there and working again in the morning. That is why a programme assesses daytime high points, moving camp and sleeping separately. Saying «I have been to 6000 m» does not confirm that you will tolerate Cólera if you went straight back down a long way afterwards.
After each night at altitude, what matters is not only how you feel on waking but how the subsequent effort goes. A good morning does not guarantee a stable day, and a bad night cannot be judged without the wider trend.
A daily briefing without competition
| Question | A useful answer |
|---|---|
| How did you sleep? | How often you woke and whether you feel recovered |
| Are you managing to eat and drink? | What you actually consumed, not what you intended |
| How has your headache changed? | The trend and the timing, not just whether it exists |
| How was the stage? | Pace, stops, load and any unusual problems |
| Any change in behaviour or coordination? | What you and the team have noticed |
The answers are not compared between climbers. A stronger athlete may respond worse to altitude. Concealing your condition for the sake of the group takes time away from the leader.
Pace, load and recovery
Starting too fast spends your reserves before altitude has even shown its effect. Pack weight, heat on the approach, cold above base camp and poor eating all add to the fatigue. A porter reduces a specific load, but does not create acclimatisation.
After a stage, what is assessed is whether you can eat, drink, get warm, set up camp and complete the following day. If you constantly need help with ordinary tasks, your real readiness may be lower than the altitude you have reached suggests.
How to choose between 17, 12 and 7 days
| Format | The basis for choosing it | The main mistake |
|---|---|---|
| 17 days | A full profile of your own for a first experience of around 7000 m | Treating more days as a guarantee |
| 12 days | Confirmed recent altitude and overnight camps | Choosing purely to fit the calendar |
| 7 days | Fresh altitude of at least 5000 m, preferably 5500+ and good recovery | Treating an old summit as current adaptation |
If the preparatory mountain did not happen, a short programme cannot be fixed by one improvised night. Other dates or a longer format are discussed before you buy non-refundable services.
Acclimatisation after another expedition
Fresh altitude can help, but fatigue, sleep debt, damaged feet and respiratory infections build up at the same time. Before running two trips together, both processes are assessed. Reaching a summit on paper does not mean you are ready to continue.
If the previous programme ended in exhaustion or in turning back on medical grounds, the decision is taken after recovery and a consultation with a doctor. A manager does not prescribe treatment and cannot guarantee that your adaptation will hold.
How contingency is used when adaptation is slow
Contingency can provide rest, change the cycle or support a safe descent. It is not a universal cure and does not oblige the team to wait until the last day. If things are getting worse, continuing to gain height does not count as rest.
After an extra day, a new assessment is made. If the trend has not improved or warning signs have appeared, the original calendar loses priority.
Decisions this article does not make
This material does not determine contraindications, dosages, the suitability of a medicine, a diagnosis or your personal safe-altitude threshold. Those are matters for your doctor and, on the route, for the leader and the medical professionals available.
A pulse oximeter, a watch and a diary provide data but do not replace clinical assessment. A good number does not cancel out worsening symptoms, and an unusual number calls for a check of both the device and the wider situation.
How the decision changes at each camp
| Point | If your condition is stable | If your condition is deteriorating |
|---|---|---|
| Confluencia | Continue monitoring and make the scheduled walk | Do not accelerate the move to Plaza de Mulas |
| Plaza de Mulas | Prepare for the first cycle | Use the rest or reconsider continuing |
| Plaza Canadá | Assess the load carry and the overnight stay | Stop gaining height and tell the leader |
| Nido de Cóndores | Compare your condition with the previous cycle | Treat the ability to descend as the priority |
| Cólera | Confirm readiness for the attempt | Do not set off merely to protect the calendar |
The table is not a medical algorithm. It illustrates a principle: a new altitude is confirmed by the actual trend, not by the fact that a camp has already been paid for or lies close to the summit.
What the climber, the group and the guide each observe
You know your own unusual sensations better than anyone, but you may underestimate changes in your behaviour. Other people notice unsteadiness, slowed movements or uncharacteristic irritability. The guide connects those observations to the route and the workload.
| Source | Useful information | Limitation |
|---|---|---|
| The climber | Headache, nausea, sleep, weakness | May conceal or normalise a deterioration |
| A partner | Gait, pace, behaviour and ordinary actions | Does not make a diagnosis |
| A device | An extra measurement, with correct technique | One number does not describe a condition |
| The guide | Trends, conditions and route decisions | Does not replace a doctor outside their competence |
Physical preparation and acclimatisation
Training improves your ability to walk for a long time, carry a load and recover, but it does not guarantee your response to thin air. A strong climber may gain height faster and so create additional risk.
Preparation should let you move slowly without surges, work for several days in a row and stay self-sufficient after a stage. Altitude adaptation is assessed separately.
Hypoxic methods before the trip
Home devices and specialist training can be discussed with a doctor and with the operator, but they are not automatically a substitute for real nights at altitude. Their protocol, reliability and tolerability should be known, not summarised by a single figure from a device.
Even after such preparation you follow the programme and report symptoms. A pre-trip method cannot be used as an argument for skipping a stage without agreement.
Different profiles within one group
One calendar does not produce the same adaptation in everyone. If people have different experience, pace and condition, the number of guides has to allow the team to respond safely. Before you pay, discuss whether the group can split and what happens if one person turns back.
On a short programme the group is assessed person by person. One climber’s strong acclimatisation does not extend to the others. If the team wants to move together, its format is limited by the weakest confirmed profile.
Why an extra day does not always solve the problem
Rest may aid recovery, but contingency does not guarantee improvement and does not cure a serious condition. After a day, a new assessment is made. If symptoms are progressing or the climber is not recovering, going higher does not become safe simply because time has passed.
Contingency may also be needed for weather and logistics. You cannot allocate all the spare days to one purpose in advance and leave the leader with no options.
A record after each high-altitude cycle
- The actual camps and sleeping altitudes
- Moving time and pack weight
- Sleep, appetite and drinking
- Symptoms and when they were reported
- The leader’s decision
- Your condition after descending and resting
The record helps you choose the next stage and preserves data for future expeditions. It is not published unnecessarily and does not replace a medical document.
Acclimatisation and your flight schedule
The dates of a programme should not be turned into a rigid international connection. The contingency inside the route belongs to the leader and may be needed for altitude, weather or a descent. You need a separate margin of your own around the trip.
| Decision | What to check | A dangerous assumption |
|---|---|---|
| Arrival | The meeting time, baggage and recovery | Landing just in time for the departure to the park |
| Contingency | Who uses it and when | Treating it as a free excursion |
| The return | The descent, the transfer and your state after the mountain | Booking a non-refundable flight straight after the programme |
| The next summit | Sleep, nutrition, injuries and retained altitude | Treating acclimatisation as the only criterion |
A rigid ticket creates pressure to keep to the calendar. The change conditions and your personal margin are discussed before the trip, not at the moment things get worse.
After illness or turning back on medical grounds
An altitude reached before things went wrong is not a ready-made clearance. First you recover and discuss going back with a doctor familiar with your case. A manager and a guide do not replace a medical assessment.
For a new programme, keep a record of the symptoms, when they appeared, the overnight camps, any medication, the decision taken, the medical documents and your condition after descending. That helps you avoid repeating the same schedule unchanged.
How to judge the quality of an acclimatisation plan
- There is a sequence of overnight camps, not just a list of summits
- Day walks are separated from moving camp
- Recovery lower down is built in after the first cycle
- Contingency is not promised as an extra summit
- Whoever takes the decisions is named
- There is a plan for splitting the group and for descending
Two trips of the same duration can produce very different profiles. Compare the actual sleeping altitudes and the logic of returning lower down.
Acclimatisation does not end at the summit
After 6962 m comes the descent, with the cold, the fatigue and the risk of mistakes still there. You keep reporting how you are and keep to the group’s pace. Reaching the summit is not permission to ignore symptoms.
Back at base camp, sleep, nutrition, injuries and your fitness to travel on are all assessed. Any decision about a next expedition is taken after you have genuinely recovered.
How to judge the result of a high-altitude cycle
Carrying a load up to a high camp and coming back down is only the first part of a cycle. Its result is judged after the rest: whether your appetite came back, whether your sleep normalised, whether you stayed self-sufficient and whether you can work again without a sharp deterioration.
Reaching Plaza Canadá, Nido de Cóndores or Cólera does not in itself mean your body is ready to sleep there. A day walk, moving camp and spending the night are three different loads. So a waypoint on a GPS cannot be separated from how long you stayed, the weight you carried, your pace and how you were the following morning.
| Observation after a cycle | What it tells you |
|---|---|
| Appetite and drinking have returned | You can replace what you spend before the next stage |
| Ordinary tasks are done unaided | The altitude reached did not require hidden excessive help |
| Symptoms ease after the descent | The next steps can be discussed on the basis of the overall trend |
| The deterioration persists or grows | The calendar cannot be the main argument for going up |
The leader decides on the balance of all the observations. A good cycle does not guarantee the summit, but it gives far more useful information than a single maximum altitude.
A useful record contains the date, the altitude you started from and turned around at, the sleeping altitude, the duration of the push, the load carried, the weather, the symptoms in the evening and your condition in the morning. Such a log lets you compare cycles on the same terms, rather than by your memory of the hardest moment.
A final checklist for the climber
- Your altitude history has been given honestly
- The format matches your fresh acclimatisation
- A doctor has discussed your personal medical questions
- Your insurance covers 6962 m
- The guide knows your medication, allergies and past reactions
- You are ready to report symptoms immediately
- Your flights do not destroy the route’s contingency
A checklist does not guarantee adaptation. It removes the gaps you can control and leaves the team more options.
Comparing altitude profiles? Open all the Aconcagua programmes and judge them not only by the number of days but by the sequence of overnight camps, the descents and the contingency built in.
Fact-checked: 17 August 2026. This article does not replace medical advice or the team’s decisions on the route.