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High-altitude travel: Mountain sickness

Published on April 12, 2024 at 8:00 / Updated on May 1, 2024 at 8:00

At higher altitudes, oxygen levels are lower. This can lead to health problems. This type of condition is called mountain sickness or altitude sickness. The risk of developing mountain sickness increases the higher and faster you climb. The symptoms can develop starting at approximately 2,500 metres.


There are several illnesses linked to altitude, acute mountain sickness (AMS) being the most common. AMS symptoms appear within a few hours or days of reaching a high altitude and subside on their own within days. The symptoms are vague and may include the following:

  • Headaches
  • Nausea or vomiting
  • Loss of appetite
  • Dizziness or vertigo
  • Fatigue
  • Weakness
  • Insomnia
  • Irritability

Severe cases of AMS are serious and can be deadly. The symptoms include the following:

  • Loss of balance
  • Drowsiness
  • Hallucinations
  • Convulsions
  • Confusion that can lead to coma

Altitude can also cause another condition that affects the lungs. The symptoms of this condition manifest initially as significant shortness of breath during physical exertion and a dry cough. Shortness of breath can later arise even at rest, along with serious difficulty breathing, coughing, and coughing up blood.


The risk of developing mountain sickness increases in the following cases:

  • You ascend too quickly
  • You normally live at a lower altitude
  • You sleep at too high an altitude
  • You overexert yourself
  • You have had the condition before

The best way to prevent mountain sickness is to ascend gradually. The following measures can also help climbers acclimatize to higher altitudes by allowing their body to adjust to lower oxygen levels:

  • Sleeping at an altitude that is lower than the maximum altitude reached during the day
  • Including a rest day every 3 to 4 days (at the same altitude)
  • Ascending gradually
    • There are specific recommendations regarding how many metres should be climbed per day. For the most up-to-date recommendations, talk to a health care professional.
  • Staying hydrated
  • Avoiding alcohol
  • Not pushing beyond a moderate intensity level

Medication can also be taken to prevent mountain sickness, especially if you've had the condition in the past.

It's important to note that physical fitness does not make you immune to altitude sickness.


The best way to treat mountain sickness is to stop climbing, return to a lower altitude, and hydrate. It's important to stop climbing immediately if you're experiencing any symptoms to prevent the condition from deteriorating and affecting the lungs or brain.

If the symptoms do not improve, it's important that you return to an altitude below 1,000 metres. You can also take medications prescribed before your trip.

When should I see a health care professional?

It's a good idea to consult a health care professional before travelling to high altitudes to discuss the risk factors of mountain sickness, the preventive measures you should take, and what medications could be used to treat the symptoms.

It's also recommended that you consult a health care professional if you develop one or more of the following symptoms during your climb:

  • Headaches
  • Nausea or vomiting
  • Loss of appetite
  • Dizziness or vertigo
  • Fatigue
  • Weakness
  • Insomnia
  • Irritability

If you get sick after you return from a trip or if you were sick while you were away, see a health care professional upon your return. Medical attention may be required.

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