The mountains beckon – higher up, to the peaks where the air is thin and the view breathtaking. Literally breathtaking: above a certain altitude, breathing becomes more difficult, performance decreases, and without proper preparation, altitude sickness threatens.

Altitude training has two aspects: preparation for stays at high altitudes (acclimatization for mountaineers, trekkers, skiers) and targeted training at altitude to improve performance (used by endurance athletes).

This guide primarily addresses the first aspect: How do you prepare for stays at high altitudes? How do you acclimatize properly? How do you recognize and avoid altitude sickness?

Physiology is complex, but the basic principles are clear: The body needs time to adapt to less oxygen. Those who don't give it this time risk their health.

Whether you're planning a climb of a 4,000-meter peak in the Alps, a trekking tour in the Himalayas, or a ski holiday at high altitudes – understanding altitude physiology makes the difference between enjoyment and danger.

As altitude increases, air pressure and therefore the partial pressure of oxygen decrease. At 3,000 meters, only about 70% of the oxygen available at sea level is available, and at 5,500 meters, only 50%.

The body reacts to this lack of oxygen (hypoxia) with adaptations: The breathing rate increases to take in more oxygen. The heart rate increases to circulate more blood. The kidneys excrete more fluid to concentrate the blood.

Over the long term (days and weeks), the body produces more red blood cells to transport more oxygen. This erythropoiesis is the actual acclimatization process – and it takes time.

The problem: If you ascend too high too quickly, the body cannot adapt fast enough. The acute compensatory mechanisms are insufficient, and the long-term ones are not yet effective. The result: altitude sickness.

Altitude zones: Up to about 1,500–2,000 m, most people hardly notice any effects. Between 2,000 and 3,000 m, adaptations begin (medium altitude). Above 3,000 m (high altitude), acclimatization becomes important. Above 5,500 m (extreme altitude), lasting adaptation is not possible—the body deteriorates over time.

Individual differences: Altitude tolerance varies greatly between people. Fitness does not necessarily correlate with good acclimatization. Genetics plays a role, as does experience.

Altitude sickness is not a weakness, but a physiological reaction to ascending too quickly. It can affect anyone, regardless of fitness or experience.

Acute Mountain Sickness (AMS): The most common form. Symptoms: headache (the primary symptom), nausea, loss of appetite, fatigue, dizziness, sleep disturbances. Typically begins 6-12 hours after reaching a new altitude.

High-altitude cerebral edema (HACE): A serious complication. Symptoms include confusion, impaired coordination (ataxia – difficulty walking straight), and altered mental status. Life-threatening – immediate descent is required.

High-altitude pulmonary edema (HAPE): Fluid accumulates in the lungs. Symptoms include shortness of breath even at rest, cough (possibly with pink sputum), decreased performance, and wheezing. It is also life-threatening – immediate descent is necessary.

Course: AMS can develop into HACE or HAPE, but it doesn't have to. The transitions can be rapid. The golden rule: If symptoms occur, do not ascend further; if symptoms are severe, descend.

Diagnosis: Primarily clinical – recognize symptoms. The Lake Louise Score is a standardized questionnaire for assessment. When in doubt: treat as altitude sickness.

Risk factors: Ascending too quickly, history of altitude sickness, exertion at altitude, dehydration. Fitness does not protect against this – being fit can even become a risk, because fit people tend to ascend too quickly.

Acclimatization takes time – there are no shortcuts. The following rules have proven effective and can prevent altitude sickness in most cases.

The ascent rule: From a sleeping altitude of 2,500-3,000 m, do not climb more than 300-500 meters per day. 'Climb high, sleep low' – you can go higher during the day, but lower again to sleep.

Plan rest days: Take a rest day at the reached altitude every 1,000 meters of elevation gain or every 3-4 days. This gives the body time to adapt.

Don't ignore it: Symptoms of altitude sickness are not weakness and won't simply go away. If you experience headaches or other symptoms: stop ascending. If it worsens: descend.

Hydration: At altitude, you lose more fluids through increased breathing and evaporation. Drink enough – your urine should be clear. But: Drinking too much isn't helpful either and can cause other problems.

Avoid alcohol and sleeping pills: Both suppress breathing and can hinder acclimatization. Abstain from alcohol for the first few days at altitude.

Start slowly: Avoid maximum exertion during the first few days at altitude. Your body is busy adapting. You can increase your pace later.

Patience: The body needs about 3-5 days for the initial adjustment to a new altitude. Give it this time, don't try to force it.

The best preparation for altitude is time spent at altitude – but that's not always possible. What can you do at home?

General fitness: Good cardiovascular fitness helps with exertion at altitude, even if it doesn't accelerate acclimatization. Endurance training, mountain hiking, and interval training are beneficial.

Increase your altitude exposure if possible: spend weekends in the mountains, go skiing at high altitudes. Any altitude exposure before the big tour helps. Even if the effects disappear quickly (after 2-3 weeks at sea level), a certain 'memory' remains.

Altitude tents and masks: Systems exist that simulate altitude (hypoxic tents, masks). These are used by professional athletes. The evidence for recreational athletes is mixed – they can improve tolerance, but do not replace genuine acclimatization on site.

Sleep optimization: Good sleep before the trip is important. Sleep is often disrupted at altitude, so arrive with a full sleep balance.

Health check: Certain pre-existing conditions (cardiovascular, pulmonary) can make stays at high altitudes problematic. If unsure: consult a doctor, ideally a specialist in altitude medicine.

Medication: Acetazolamide (Diamox) can be used prophylactically to support acclimatization. It is not a miracle cure and does not replace a slow ascent, but it can be helpful during a rapid ascent (flight to Lhasa, short expedition). Prescription required – discuss with a doctor.

Nutrition at high altitudes is more important than often thought. The body works harder and needs appropriate support.

Increase your calorie intake: Your basal metabolic rate is higher at altitude, and this is compounded by the physical exertion. Many people eat less at altitude (loss of appetite is a symptom of acclimatization), but they need more. Consciously eat enough, even if you don't feel hungry.

Emphasize carbohydrates: Carbohydrates are the most efficient fuel at high altitudes – they require less oxygen to metabolize than fats. Carbohydrate requirements are higher, while fats are utilized less efficiently.

Iron: The body needs iron to produce red blood cells. Consume iron-rich foods (red meat, legumes, spinach) in the weeks leading up to and during your stay at altitude. If you have a known iron deficiency, supplementation is necessary.

Fluids: Hydration is essential, but the recommendation to 'drink as much as possible' is outdated. 3-4 liters per day is recommended for active individuals; urine should be clear to pale yellow. Avoid overhydration – hyponatremia (too little sodium in the blood) is also a risk.

Caffeine: In moderation, caffeine is acceptable and can help with headaches. However, it is a diuretic and can contribute to dehydration. Moderate amounts are sufficient.

Alcohol: Avoid during the first few days of acclimatization. Later, moderate consumption is possible, but keep in mind: The effects are intensified at altitude, and dehydration is promoted.

When altitude sickness occurs, quick and correct action is crucial. The most important treatment is simple: descent.

For mild AMS (headache, mild nausea): Do not continue ascending. Rest, drink fluids, and take painkillers (ibuprofen, paracetamol) for headaches. If it improves: proceed carefully. If it stays the same or worsens: descend.

For moderate to severe AMS: Descending is the treatment. A reduction of 300-1,000 meters in altitude usually makes a big difference. Oxygen if available. Acetazolamide can help.

In case of HACE (confusion, ataxia): Medical emergency. Immediate descent, even at night, even in bad weather. Dexamethasone (a strong corticosteroid) can be lifesaving. Oxygen. Portable hyperbaric chamber (Gamow bag) if descent is not possible.

HAPE (shortness of breath at rest): This is also an emergency. Immediate descent is required. Oxygen is especially important here. Nifedipine can help. Avoid exertion (the heart is already working at its limit).

Emergency medications: On expeditions and trekking tours at high altitude: Carry dexamethasone and nifedipine as emergency medications (after consulting a doctor). Know when and how to use them.

Descent is therapy: that's the most important point. Medication can buy time, but it doesn't replace descent. 500-1,000 meters lower can mean the difference between life and death.

Endurance athletes use altitude training to improve oxygen transport capacity – more red blood cells, better performance at sea level.

The principle: Live (or sleep) at altitude to stimulate adaptations, but train at lower altitudes to maintain training quality. 'Live high, train low' is the established paradigm.

Optimal altitude: For erythropoiesis stimulation: 2,000-2,500 m sleeping altitude for at least 3-4 weeks. Shorter stays or lower altitudes produce less of an effect.

Training altitude: Intensive training sessions are better performed at lower altitudes (below 1,500 m) to maintain quality. At 2,500 m, maximum performance is reduced, making interval training less effective.

Timeline: The adaptations take time (2-3 weeks), and after returning to sea level, they only last for a limited time (2-3 weeks). Timing before important competitions is crucial.

Altitude tents and masks: Simulate altitude at home. Can partially reproduce the effects of altitude without having to travel. Used by professional athletes. Usually overkill for amateur athletes.

Individual response: Not everyone reacts the same way to altitude training. Approximately 20% of people are 'non-responders' – they show little adaptation. The response depends on genetics and initial condition.

Risks: Overtraining is more likely at altitude. Sleep quality often suffers. Maintaining the balance between training stimulus and recovery is more difficult.

Certain groups require special considerations when staying at high altitudes.

Children: Often have difficulty communicating symptoms. Changes in behavior (irritability, lethargy) can be signs of altitude sickness. Ascend cautiously and observe closely. Infants and toddlers should not be taken to high altitudes (above 2,500 m).

Older people: Aging alone is not an obstacle. However, pre-existing conditions are more common, and their reserves may be lower. Consult a doctor before undertaking demanding high-altitude expeditions. Ascend slowly.

Cardiovascular diseases: Coronary artery disease, heart failure, arrhythmias – altitude puts additional strain on the heart. Obtain medical clearance, discuss medications, and proceed with a conservative ascent. If your condition is unstable: avoid high altitudes.

Lung diseases: COPD, asthma – impaired lung function becomes more relevant at altitude. Medical consultation is essential. Monitor oxygen saturation. Moderate altitudes are often possible, high altitudes more problematic.

Pregnancy: Generally, altitudes above 2,500-3,000 m are not recommended, especially during the first trimester. The unborn child is more sensitive to hypoxia. Consult your doctor.

Migraine: Altitude can trigger migraines. Discuss preventative measures, stay well hydrated, and ascend slowly.

Anemia: Low hemoglobin levels worsen altitude tolerance. Before planned stays at high altitudes: Check blood count and optimize iron levels.

At what altitude do I need to start thinking about acclimatization?

The effects become relevant for most people at sleeping altitudes of around 2,500 meters. Some react sooner, some later. The rule of thumb: Ascend slowly from 2,500-3,000 meters and watch for symptoms.

How quickly can I advance?

Sleeping altitude above 3,000 m: maximum 300-500 m ascent per day. Take a rest day every 1,000 m or every 3-4 days. 'Climb high, sleep low' – you can ascend higher during the day, but descend to a lower altitude to sleep.

Does fitness protect against altitude sickness?

No. Fitness helps with exertion, but acclimatization is a separate process. Very fit people even tend to ascend too quickly because they feel capable. Altitude sickness affects fit and unfit people alike.

What are the first signs of altitude sickness?

Headache is the primary symptom. Other symptoms include nausea, loss of appetite, fatigue, sleep disturbances, and dizziness. If these symptoms occur: do not ascend further; if they worsen: descend.

Does drinking plenty of fluids help against altitude sickness?

Adequate hydration is important, but excessive drinking does not prevent altitude sickness. Aim for 3-4 liters per day during activity; urine should be clear. More is not better – too much can even be problematic (hyponatremia).

Should I take Diamox (acetazolamide)?

Diamox can aid acclimatization, especially during rapid ascent (flying to high altitudes). It does not replace slow ascent and has side effects (tingling, increased urination, altered taste). Discuss with a doctor and ideally test before traveling.

Can I simply 'sleep off' altitude sickness?

No. Altitude sickness doesn't go away with rest at the same altitude – it can even worsen. If symptoms persist or worsen: descend. That's the treatment.

How long do the adaptations last after exposure to high altitude?

The elevated red blood cell count persists for about 2-3 weeks after returning to sea level, then it normalizes. Altitude tolerance ('altitude experience') can last longer, but is more difficult to quantify.

Is it dangerous to go to high altitudes immediately after a flight?

Yes, that's risky. Flying to Lhasa (3,650 m) or Cusco (3,400 m) means suddenly being at high altitude without acclimatization. Spend the first 24-48 hours resting and avoiding exertion. Diamox can help. If you experience severe symptoms, seek medical help.

Can I go to high altitudes if I have asthma?

With well-controlled asthma, moderate altitudes (up to about 3,000 m) are often possible. The dry, cold air can trigger symptoms. Take your medication with you, and always carry your inhaler. Consult your doctor before traveling, especially for high altitudes.