Altitude Sickness: When trekking in the Himalaya there is always a real danger of mild to serious problems related to altitude. The complaints are collectively known as Acute Mountain Sickness (AMS). It is important that trekkers understand that they will be affected to a greater or lesser extent when they ascend to altitudes over about 3000 meters. As you climb higher the atmospheric pressure falls and the amount of available oxygen also falls. The body will adjust to cope with this by altering the characteristics of your blood in order to utilize better the lower oxygen levels available to it. This process takes time and can vary from individual to individual. Indeed, individuals can experience different rates of acclimatization on separate visits. So, having acclimatized well on a previous visit is no guarantee of quick acclimatization subsequently.

The mechanics of acclimatization are not well understood but it has been proved that a number of factors have a positive effect. By far the most important is regulating your rate of ascent when traveling in excess of 3000 meters above sea level. As a general rule you should not gain more than 400-500 meters a day and have a rest day every fifth day. Maintaining a good fluid intake and urine output has also been proved to be effective in combating the effects of altitude. The dry air of the mountains tends to dehydrate you so an increased fluid intake is necessary. Try to drink at least four liters of water a day.

Prophylactic medication should not be required to aid acclimatization unless specifically prescribed by a physician skilled in the treatment and prevention of altitude sickness. Fitness may have some effect on speedy acclimatization but being young and fit does not guarantee immunity. The only age concern is for the very young who may not be able to describe their symptoms to their parents. For this reason it is unwise to take very young children to altitudes above 3500-4000 meters. Symptoms of AMS may be mild or severe and the victim can develop severe symptoms very rapidly if the mild effects are ignored. The most commonly reported complaints are:
-Headache that may respond to pain killers but then returns
-Loss of appetite -Swelling of the limbs
-Dizziness/light-headedness
-Difficulty in sleeping
-Irregular breathing -Nausea -Unusual weariness

Poor coordination and slurring of speech All or some of these symptoms may be present in mild cases of AMS but they can rapidly worsen and become dangerously debilitating. In particular, as the symptoms worsen the victim will often become irrational and difficult to reason with. Their ability to make sensible decisions for themselves is increasingly impaired and their companions may be their only hope of survival. This is a compelling reason for never trekking alone at altitude.  In the final stages of altitude sickness severe problems start to appear which can rapidly lead to loss of consciousness and death if untreated. Two forms of AMS are generally recognized. One or both may be present and either is extremely serious.