Staying at High Altitude

Altitude Illness

At high altitude, the lower air pressure means that less oxygen is available to the body. This can lead to different forms of altitude illness. Individual susceptibility varies considerably, and one of the most important risk factors is how quickly you ascend to high altitude.

Above 3,000 metres, you should preferably increase your sleeping altitude by no more than about 300 metres per day, and certainly by no more than 500 metres per day. To have a reasonable chance of reaching the summit of Kilimanjaro without major problems, for example, you should normally allow at least seven days for the ascent from around 3,000 metres. Faster ascents considerably increase the risk of altitude illness and reduce your chances of reaching the summit.

Being physically fit or well trained does not protect you against altitude illness – anyone can be affected. The risk is greater if you have previously experienced altitude illness. Alcohol, sedatives and sleeping tablets should be avoided during the initial period of acclimatisation, as they may interfere with breathing during sleep.

Remember that air travel can take you rapidly to high-altitude destinations such as La Paz (approximately 3,650 m), Addis Ababa (approximately 2,350 m) or Mexico City (approximately 2,250 m), leaving little or no opportunity for gradual acclimatisation.

Reducing the Risk of Altitude Illness

  • Ascend gradually whenever possible.
  • If possible, spend 1–2 days at around 2,500–2,800 metres before continuing to higher altitude.
  • Above 3,000 metres, preferably increase your sleeping altitude by no more than about 300 metres per day, and certainly by no more than 500 metres per day.
  • Allow extra time for acclimatisation as you ascend.
  • Drink enough to avoid dehydration, but do not force yourself to drink excessive amounts of fluid.
  • Keep warm.
  • Avoid strenuous exertion if you feel tired or unwell.
  • Never continue to a higher sleeping altitude if you have symptoms of altitude illness.

Climb High – Sleep Low

Above 3,000 metres, you should preferably sleep no more than about 300 metres higher than the previous night, and certainly no more than 500 metres higher. You can ascend higher during the day but return to a lower altitude to sleep. It is your sleeping altitude that is particularly important for acclimatisation.

Diamox (Acetazolamide)

Diamox (acetazolamide) is a medicine that can speed up the body's acclimatisation to altitude and is sometimes used to prevent acute mountain sickness, particularly when rapid ascent cannot be avoided, such as when flying directly to a destination above 3,000 metres.

Preventive treatment should be discussed with a doctor before travelling. Common side effects include increased urination, tingling or numbness in the fingers, toes or around the mouth, and sometimes dizziness. Carbonated drinks may also taste different while taking acetazolamide.

Acetazolamide may not be suitable for people with certain kidney conditions and can interact with some medicines. Discuss your medical conditions and regular medication with your doctor before using it.

Important Information About Diamox

Diamox does not make it safe to continue ascending if you develop symptoms of altitude illness. Never use the medicine as a reason to ignore symptoms or continue to a higher sleeping altitude while you are unwell. Doing so can allow altitude illness to progress to a life-threatening condition.

Acute Mountain Sickness (AMS)

Acute Mountain Sickness (AMS) is common at high altitude and affects a substantial proportion of people who rapidly ascend to around 3,500–4,000 metres.

  • headache
  • dizziness
  • sleep disturbance
  • loss of appetite
  • nausea or vomiting
  • tiredness or weakness

Symptoms usually develop within the first 2–12 hours after arriving at a higher altitude, often during or after the first night, and mild symptoms may resolve within a few days as the body acclimatises.

If You Develop Symptoms of AMS

Do not continue to a higher sleeping altitude. Rest and give your body time to acclimatise. When the symptoms have completely resolved, you can continue your ascent gradually. If symptoms become worse despite resting at the same altitude, descend to a lower altitude.

Severe Altitude Illness – HAPE and HACE

More serious and potentially life-threatening forms of altitude illness can develop at high altitude. Although the risk increases with altitude, HAPE and HACE can occur below 4,000 metres and should not be regarded as conditions that occur only above a particular altitude.

  • HAPE (High-Altitude Pulmonary Oedema) – fluid accumulates in the lungs.
  • HACE (High-Altitude Cerebral Oedema) – swelling of the brain.

Life-Threatening Conditions

Both HAPE and HACE are medical emergencies and can progress rapidly. Immediate action is required.

Symptoms of HAPE

  • increasing shortness of breath, particularly breathlessness at rest
  • marked tiredness or weakness
  • persistent or worsening cough
  • chest tightness or congestion
  • noisy or crackling breathing
  • frothy or blood-stained sputum in advanced cases

Symptoms of HACE

  • severe or worsening headache
  • loss of coordination or difficulty walking normally
  • nausea or vomiting
  • confusion or unusual behaviour
  • marked drowsiness
  • altered consciousness
  • unconsciousness or coma in severe cases

Watch your travelling companions carefully for signs of severe altitude illness. A person developing HACE may not realise how seriously ill they have become. The condition can deteriorate rapidly, and coma may develop within hours in severe cases.

If HAPE Is Suspected

  • Begin descent immediately, preferably by at least 500–1,000 metres or until symptoms clearly improve.
  • Keep physical exertion to an absolute minimum and assist or carry the person if necessary.
  • Give supplemental oxygen if available.
  • Keep the person warm.
  • Seek emergency medical assistance as quickly as possible.
  • If immediate descent is impossible, supplemental oxygen or a portable hyperbaric chamber may be lifesaving if available.

If HACE Is Suspected

  • Begin descent immediately, preferably by at least 500–1,000 metres or until symptoms clearly improve.
  • Keep physical exertion to an absolute minimum and assist or carry the person if necessary.
  • Give supplemental oxygen if available.
  • Keep the person warm.
  • Seek emergency medical assistance as quickly as possible.
  • If immediate descent is impossible, supplemental oxygen or a portable hyperbaric chamber may be lifesaving if available.

Cold and Frostbite

High-altitude travel often also involves exposure to cold. The combination of wind, wet clothing, exhaustion and inadequate energy intake can rapidly cause cold injuries, even when the air temperature is above freezing.

Preventing Cold Injuries

  • Dress in several layers.
  • Keep yourself and your clothing dry and warm.
  • Carry spare warm clothing.
  • Remember a warm hat, gloves or mittens and spare socks.
  • Eat and drink adequately.
  • Keep moving when appropriate to maintain circulation and body warmth.
  • Seek shelter from severe weather.
  • Avoid alcohol.

Wind Increases Heat Loss

Wind can make conditions feel considerably colder than the measured air temperature. The combination of cold, wind and wet clothing greatly increases the risk of frostbite and hypothermia.

Superficial Frostbite

Superficial frostbite may cause numbness, tingling or stinging pain and pale or waxy skin that remains relatively soft.

Protect the affected area from further cold. A mildly affected area may be gently rewarmed using body heat, for example by placing cold fingers in the armpit. Do not rub or massage frostbitten skin.

Deep Frostbite

With deeper frostbite, the affected area may become hard, numb and pale or waxy. After thawing, significant swelling, blue-red discolouration and blistering may develop. Severe frostbite can result in permanent tissue damage and tissue death.

Do not deliberately thaw a severely frostbitten body part if there is a significant risk that it will freeze again. Refreezing after thawing can cause considerably greater tissue damage.

Once shelter is available and refreezing can be prevented, rapid rewarming in a water bath at approximately 37–39°C is recommended. Give appropriate pain relief if needed. Do not rub or massage the affected area, and seek medical attention as soon as possible, particularly for deep or extensive frostbite.


Senast uppdaterad 2026-09-02