Travel excursions that involve travel at high, or even very high altitude, are becoming

more common.

The following is a classification of what is meant by high altitude:

  • high altitude – is anywhere above 2400m and below 3658m e.g. Bogota, Quito

and Cusco

  • very high altitude – is anywhere above 3658m and below 5500m e.g. La Paz,

Mount Kenya, Mount Kilimanjaro and Everest base camp.

Issues that need consideration prior to travel at high altitude include:

  • increased exposure to sun and ultraviolet light and the need to preventing


  • the climate can be cold especially at night
  • access to medical care may be difficult
  • there is a risk of Acute Mountain Sickness (AMS).


Acute Mountain Sickness (AMS)

Atmospheric pressure decreases with altitude. Although the percentage of oxygen in air

remains the same, the barometric pressure reduces and the amount of oxygen that gets

into the lungs through breathing and the amount of oxygen in the blood is reduced. This

is known as hypoxia and it is the body’s’ response to hypoxia that causes acute

mountain sickness.

Prevention of AMS

AMS is common at high altitude and more than 50% of travellers who go to 3500m or

above will be affected. There is no way to predict who will be affected. The main way to

prevent AMS is through gradual ascent.

There is some evidence that use of a drug called acetazolamide (also known as

Diamox) can reduce the chance of AMS occurring. This is not given to all travellers to

high altitude as a matter of routine, and the decision on whether it should be taken or not

is for the individual and the advising healthcare professional, and not the excursion

organisers. Where appropriate, it can be prescribed by a physician.

Symptoms of AMS

Symptoms of AMS can be mild or severe and are often unpleasant. Common symptoms


  • dizziness
  • fatigue, flu like symptoms
  • headache
  • irregular breathing during sleep
  • loss of appetite nausea and/or vomiting
  • palpitations
  • swelling of the face, hands and feet
  • breathlessness.

Key Message: If symptoms of AMS arise then ascent must be stopped. If

symptoms do not resolve then a rapid descent is required. If ignored, AMS is a

potentially life-threatening condition.

Treatment of AMS

The key to treatment of AMS is to descend to a lower altitude. Over and above this, the

actual medical treatment of the condition is too complex for the purposes of this

document. If an excursion is planned to an area of high altitude, at least of the team

leaders should have prior experience of travel to high altitude and know what to do if

someone develops symptoms of AMS. In addition, specialist pre-travel health advice

should be sought in advance.

Key points:

  • seek specialist advice if travelling to an area of high or very high altitude
  • one of the group leaders should have prior experience of travel to high altitude
  • the key to prevention of AMS is gradual ascent
  • group members must report symptoms of AMS to the group leader
  • if ignored, AMS can rapidly become a potentially life-threatening condition
  • rapid descent is the key to treatment of AMS.

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