A person who lives at one hundred and fifty meters above sea level and is planning a trip to the Andes usually asks one question: how to prepare at home. The answer is unpleasant and very useful: at home, the smaller part of the task is solved. The main part happens on site and depends on how fast you gain altitude.
This is not a reason to do nothing. It is a reason to set priorities correctly, because the altitude preparation market is built the other way around: what is sold the loudest is what has the weakest effect.
Order of things by strength of influence
- Speed of altitude gain on site. The only factor with a truly strong evidence base.
- Staged ascent — several days at moderate altitude before climbing higher.
- Medication prophylaxis at medium and high risk — a question for a doctor.
- Physical base and iron stores.
- Hypoxic preparation at home. Not because it is useless, but because the volume requirements are high and the evidence is weaker.
And an important point right away, because this is the most common misconception: good physical fitness does not protect against altitude sickness. Moreover, a trained person is at greater risk — they are able to go faster than acclimatization allows, and that is what lets them down.
The five hundred meter rule
International recommendations on altitude sickness set the norm as follows: above 3000 meters, sleeping altitude increases by no more than 500 meters per day, and every 3–4 days a day without gain is taken — approximately every thousand meters.
The key word is sleeping altitude. What counts is not the maximum point of the day, but where you sleep. Hence the classic scheme “climb high — sleep low”: during the day go up a few hundred meters higher, in the evening descend to sleep.
The step is counted from the last overnight stay, not from sea level and not from the point of arrival. If you arrived and sleep at 3600, the next overnight stay is no higher than 4100, the one after tomorrow — no higher than 4600, and somewhere here a day without gain is already needed. The day of arrival does not enter this arithmetic at all: it is already a jump that you compensate for, not continue.
And the main caveat to the whole section: the gain rule describes a healthy person without symptoms. If your head hurts, the step followed guarantees nothing and you must not go up, even if the schedule says you should.
Real routes rarely allow you to keep the step perfectly. Then a relaxed rule applies: the average speed for the whole trip — the total gain divided by the number of days — must still be below 500 metres per day, and acclimatisation days are placed before or after the forced jump.
It is worth looking at your route through the lens of this rule. Flying from sea level straight to La Paz (3600 m) or to Cusco (3400 m) means a gain of three and a half kilometres in a day. No safe scheme allows that. So the first two days on site — no exertion, no alcohol and no further altitude gain — and that is not overcaution but compensation for the jump already made.
How to tell it has started
Mountain sickness is diagnosed using the Lake Louise score: three points or more with headache as a mandatory symptom plus at least one other — dizziness, weakness, nausea, disturbed sleep. Three to five points is considered mild, six and above moderate to severe.
A headache at altitude is not something to push through. It is a mandatory sign of the diagnosis, and it should be treated as a signal.
Three rules are worth knowing by heart:
- With any symptoms, do not go higher until they have completely resolved.
- If symptoms worsen or do not go away within a day or two — go down. Descending works better than any medication; aim for 300 to 1000 metres until you feel better. You can resume elevation gain only after the symptoms have completely disappeared, and not on the same day.
- Unsteady gait, confusion, strange behaviour — this is cerebral oedema. Descend immediately, and the person must not be left alone.
- Shortness of breath at rest that does not ease after resting, a cough, pinkish frothy sputum, inability to walk — this is pulmonary oedema. It develops within hours, so descent is not delayed until morning. You need to descend at least a thousand metres and with minimal effort: without a backpack, with assistance, by transport if available. Forcing a person to walk down on their own legs when they cannot is a mistake: exertion worsens the oedema.
Medications: what to ask a doctor
Prescriptions are made by a doctor, and this is not a formal disclaimer: both medications below have contraindications and side effects, and the choice depends on your risk and history. It is worth coming to the doctor with specific questions.
The main preventive agent is acetazolamide: of the two, it is the only one that speeds up acclimatisation itself. Dexamethasone is also permitted by guidelines for prevention in adults at moderate and high risk, but as a substitute when acetazolamide is not tolerated, not as an equal choice. The difference is fundamental.
Dexamethasone relieves symptoms but does not speed up acclimatisation. This leads to a rule more important than all the rest of the pharmacology: if you feel better after a tablet, it does not mean the mountain sickness has stopped. The decision to ascend is made based on symptoms without the medication, not on how you feel while taking it. While a person is "holding up" on dexamethasone, ascent is forbidden.
It is more useful to know something else — the list of what the guidelines call ineffective. It includes ginkgo biloba, inhaled budesonide, salmeterol, oxygen canisters and oxygen bars. Coca leaves and coca mate, offered on every corner in the Andes, have simply not been studied as a preventive measure — they cannot replace the rules of altitude gain.
Hypoxic tents and masks: the long conversation
Here it's worth honestly separating two views, because they diverge.
International guidelines give hypoxic tents a weak rating — benefits come only from long exposures, more than eight hours a day for several weeks. Short sessions of fifteen to sixty minutes or "a few hours a couple of times before a trip" almost certainly provide no benefit. A hyperbaric chamber is more effective than a tent or mask.
That is, most of what is sold as "altitude preparation" in a fitness format falls exactly into the zone described as: too little to work.
The Russian school of hypoxic training works with noticeably larger volumes. Irina Zelenkova, candidate of medical sciences, a specialist at the RCC Innovation Center, describes preparation for Everest as follows: sleeping in a hypoxic tent according to a 21-day program with ascent from 1800 to 5000 meters within the block, plus interval breathing — thirty seconds through a mask with air at 10% oxygen, thirty seconds with normal air, with periods selected by pulse oximeter. The "live high — train low" model means 12–14 hours of hypoxia at night while training at low altitude, and 19–20 days are allocated for the program.
Protocols from the educational course "Hypoxic Training" give even more specific figures: passive interval hypoxia — 60–100 minutes a day, 14–30 procedures per course, at 10–12% oxygen, in cycles of five minutes of hypoxia and three minutes of recovery. Interval work with exercise — 30–40 minutes, in blocks of 2–6 weeks.
It's important how to treat these figures. These are methodological materials of a specific school, not an international consensus: "60–100 minutes a day" is not a universal norm that can be taken and applied to yourself. They are given so that the scale of the task is visible.
And the scale is this: the divergence between schools is not so much in principle as in volume, and everywhere it's about weeks, not a few sessions. The practical conclusion is one — either do this seriously and under a doctor's supervision, or don't count on this point at all, because a half-measure simply won't reach the required dose. And none of the protocols cancels the rules of altitude gain on site. Contraindications are stated directly in the course: subcompensated heart and lung diseases.
What is better studied and works more reliably is a staged ascent: six to seven days at 2200–3000 meters before ascending higher noticeably reduces the risk. If the route allows inserting such a stage, it is more advantageous than any tent.
Iron: the quiet limiter
Adaptation to altitude includes an increase in the blood's oxygen capacity, and there's nothing to build it from if the body lacks iron. Therefore, ferritin and a complete blood count should be tested 8–10 weeks before the trip: if stores are low, replenishing them takes weeks, not days.
Next, it's important not to confuse two different things. The daily intake of iron is around 18 mg for women and 8 mg for men — this is about a normal diet. Replenishing a detected deficiency involves completely different doses, a different duration, and monitoring by tests, and it is prescribed by a doctor. You cannot take the intake norm as a "preparation dose".
Hence the timelines. If ferritin is fine, a month before the trip it's enough to keep an eye on your diet and absorption: iron works together with folate, B vitamins and vitamin C. If a deficiency is found, four weeks may not be enough — that's why tests are done 8–10 weeks out, so the doctor has some buffer.
Physical preparation: 12–16 weeks
There's no separate type of training that prepares you specifically for altitude. You need a large aerobic volume and legs that are endurance-ready for long work with a backpack.
Weeks 1–6 — base. Aerobic volume in zones one and two, about 80% of time at low intensity. Understanding heart rate zones here isn't decoration, it's a working tool. A long run once a week, strength training twice a week.
Weeks 7–12 — specificity. The key workout of the block is a long outing of three to six hours with an 8–12 kg backpack. At altitude you'll be walking long and slow, not running, and that's what you need to prepare for. Add stairs and long climbs here too: the technique of power hiking uphill saves more than it seems. Descents are trained separately — they wreck your legs more than climbs, and on trails you have to descend a lot.
Strength training doesn't go away in this block: single-leg movements and work on your calves and feet directly affect how you get through a day on scree.
The last 2–3 weeks — taper. Volume down by 30–40%, intensity maintained. Arriving in the mountains rested matters more than arriving maximally trained. The last hard workout — no later than ten days before departure.
What to take from your data
A separate note on water, because it goes against intuition: you shouldn't drink beyond thirst. "Preventive" water loading doesn't protect against altitude sickness, but it does create a risk of diluting your electrolytes. This is specifically about forced drinking on a schedule — cutting back on water at altitude, on the contrary, is not allowed: dehydration symptoms resemble altitude sickness and blur the picture. Drink to thirst, but do drink.
A pulse oximeter is useful on site, with a caveat: saturation alone doesn't make a diagnosis and is reduced in everyone at altitude. What matters is the trend — it's alarming when the reading drops day after day at the same altitude, or when low values come together with shortness of breath at rest.
The same principle applies to heart rate: a morning resting heart rate that's 10–15% above your usual for several days in a row is a sign that acclimatization isn't progressing and it's time to add a day without gaining altitude.
And some good news to finish: acclimatization isn't lost right away. The ability to work at altitude persists for weeks after descending, and some changes last for months. So descending to the plains mid-route doesn't reset what you've built, and a second trip in the season feels easier than the first.
But "easier" here doesn't mean "faster". The adaptation you've kept doesn't give you the right to shorten the elevation gain schedule a second time: the 500-metre rule and days without gain apply just as they did the first time.
The main takeaway stays the same. A backup day in the schedule is worth more than any gadget: if acclimatisation goes badly, there are only two answers that work — time and descent, and both require slack in the plan.
In 1trAIner, the AI coach builds your plan as a planning cascade Season → Month → Week → Day. If you have a trip to the mountains in your calendar, preparation unfolds backwards from it: base, a block with a backpack, a taper before departure. First 7 days free.
This material is for information only and does not replace a doctor's consultation. The use of any medication for the prevention and treatment of altitude sickness, as well as clearance for hypoxic training, is determined by a doctor. If symptoms of mountain sickness appear, the decision on whether to continue the ascent is made in favour of descending.
