How to Prevent Mountain Sickness

You feel…
You feel as if you have a bad hangover. Your head aches, you are a bit dizzy, you get short of breath with any exertion and you can’t sleep.

If you’re on a mountain and have risen to altitude too quickly, these are signs not of drunkenness, but of acute mountain sickness (AMS).

Thin Air
The higher you go above sea level, the thinner the air becomes. Barometric pressure decreases (although the air still contains 21% oxygen). Every breath you take contains fewer molecules of oxygen. You find yourself breathing faster and deeper in order to obtain oxygen, especially when you are doing something strenuous, such as climbing or walking uphill.

People usually do not experience difficulty when ascending rapidly to modest altitudes, in, for example, a cable car or a train, some do, particularly the elderly, babies and small children, those with lung or heart conditions. You do not get altitude sickness in an aeroplane either, because the air within the craft is pressurised.

Understanding What Happens
The trouble usually arises, if at all, above about 2,500 metres. It is not the decreased availability of oxygen alone that causes acute altitude sickness, but the fact that carbon dioxide accumulates in your blood. Your body may not recognize that you need to increase your rate of breathing to dispose of it. An excess of CO2 upsets your body’s acid–alkali balance, which will in turn allow fluids to form in the wrong places. One serious consequence can be pulmonary oedema, or fluid on the lungs, which causes breathlessness, may even lead to respiratory failure. Another is cerebral oedema, when fluid collects in the skull, causing severe headaches and the risk of permanent damage or death.

Can I Get Mountain Sickness?
Who can get acute mountain sickness? The answer is: anyone. It is no respecter of age, gender, physical fitness or previous experience at altitude. Some people get sick on one trip and not on another, even though the ascent and timings are the same. There is no way to predict who is likely to develop AMS.

Need To Know
Now you may be thoroughly frightened about that impending trekking trip to Nepal, or ascent of a mountain in the Rockies. Don’t be. You just need to know that mountain sickness is always caused by ascending too quickly. Prevention is better than cure, follow the rules and the guidance of people who have more experience than you. One rule is to take several days climbing to 3,000 metres and thereafter, not to climb more than 300 metres in a day.

Climb High – Sleep Low
Mountaineers follow the rule: "climb high, sleep low". This means they climb maybe 1,000 metres or a bit more in a day, but then come back down again to sleep at a lower altitude. You need to do this over several days, so that your body adapts gradually to a higher altitude. Thus, your "zone of tolerance" extends higher up the mountain each day.

If you have not acclimatized properly, you may become ill. Look out for symptoms in yourself (as well as in others in your party, if you yourself feel fine). Headaches, clouded judgement and confusion, swollen ankles, fatigue beyond what you would normally feel on exertion, insomnia, "periodic breathing" (involuntarily holding your breath), nausea and decreased frequency of urination are all symptoms, which need to be attended to if you are to prevent rapid deterioration in your health. And attended to immediately. Don’t wait until daybreak: move down to a lower elevation straight away. This is the only sure way to alleviate the symptoms and prevent further, more serious illness. Even moving down 500 metres may save the life of someone with AMS. At altitude, you become dehydrated, drinking plenty of fluids is another measure both to prevent and to treat mild cases of mountain sickness.

Finally, there is a medication called acetazolamide (trade name Diamox, not available everywhere, however), which can prevent AMS, if taken before an ascent or markedly decrease the symptoms if a bout of illness or headaches occur.

The message is: acclimatise slowly; but if you get signs of sickness at altitude, don’t be afraid to say so. There is no shame in having AMS, but it is not OK to die from it.

Harish Kohli is an avid traveller who likes to share good adventure travel ideas. He is also CEO of


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