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  » Advice for travelers  »  Altitude sickness

The cause
High altitude holidays are increasingly popular. In South America they include crossing Andean passes often above 4000 metres. Trekkers in the Himalayas, especially in Nepal, often reach similar heights. Kilimanjaro in Tanzania and Mount Kenya are both more than 5000 metres.

Only those healthy and trained should attempt such expeditions, and if in doubt medical advice should be taken. All including the physically fit can get acute mountain sickness during rapid ascent if staying for more than 12 hours above 2500 metres. It affects all ages including children when the symptoms may be more difficult to recognise.

The altitude difference undergone in 24 hours is the determining factor. From 3000 metres and higher, the risk increases when the altitude difference between encampments exceeds 300 metres.

  • High Altitude:2400m to 3658m. (e.g. Cochabamba in Bolivia = 2550m. Bogota in Columbia = 2645m. Quito in Ecuador = 2879m. Cuzco in Peru = 3225m)
  • Very High Altitude: 3658m to 5500m. (La Paz in Bolivia = 3658m. Lhasa in Tibet, China = 3685m. Base camps of Everest in Nepal = 5500m)
  • Extreme Altitude: 5500m to 8848m (e.g. the summit of Mount Everest).

Signs of mountain sickness
Early signs of acute mountain sickness include headache, nausea, anorexia and insomnia. If vertigo, vomiting, apathy, staggering and dyspnoea occur, immediate accompanied descent is essential. Failing to descend may be fatal.

Avoid ascents of greater than 300 metres per day if starting from above 3000 metres. If early signs of mountain sickness appear, rest for a day at the same altitude. If they persist or increase, descend at least 500 metres.

Acetazolamide (Diamox) is sometimes be used as prophylaxis for mountain sickness when a gradual ascent cannot be guaranteed. It should NOT be used as an alternative to a gradual ascent. It acts on acid-base balance and stimulates respiration. It should be combined with a good fluid intake. It should not normally be used in young children. 

Minor symptoms
Initially simple analgesis (eg: paracetamol) for headaches. Sleeping pills should be avoided if possible. Seek medical advice.
More serious or persistent symptoms
Immediate evacuation or descent; oxygen if available. Seek urgent medical advice but do not let this delay descent - steroid drugs and/or nifedapine may be necessary. 

A useful address
For information sheets available to Doctors/Climbers/Trekkers contact the British Mountaineering Council, 177-179 Burton Road, Manchester, M20 2BB. Tel:0161 445 4747. Fax:0161 445 4500. Web-site address: