One of the main health concerns when mountaineering are the effects of high altitude to a person. Different people have different reactions when exposed to it. Undoubtedly, this is due to several intervening variables. The major issues to watch out for include: altitude illnesses, hypothermia and frostbite, and dehydration.
The most important thing is to avoid AMS by acclimatizing properly by a gradual ascent. A recommended rate of ascent is to climb no more that 500 meters a day over an altitude of 3000 meters. In addition, you could also take a rest day every third day. If this is not possible, because of the position of the huts or campsites, you could also do staging, where you remain at an intermediate altitude between 3000 and 4000 meters for an extra day before ascending any further.
Also, always sleep at a lower altitude than the highest point reached that day. Sleeping at least 1,500 to 2,000 feet in elevation higher that the night before has been shown to help safely acclimate the body more than sleeping higher than that altitude gain.
Hydrate! Hydrate! Hydrate!
Although dehydration does not *cause* altitude sickness, it does decrease physical performance and the ability to generate heat. This will contribute to chilling and fatigue, which then could lead to altitude sickness, as well as hypothermia and frostbite. Drink at least 4 liters of water a day. Six liters is not too much. It is actually during sleep that your body uses water to help acclimate (adjust) to the atmospheric pressures of being at higher elevations.
The major cause of altitude illnesses is going too high, too fast. Given time, your body can adapt to the decrease in oxygen molecules at a specific altitude. This process is known as acclimatization and generally takes 1-3 days (per atmosphere) at that altitude. For example, if you hike to 10,000 feet (3,048 meters), and spend several days at that altitude, your body acclimatizes to 10,000 feet (3,048 meters). If you climb to 12,000 feet (3,658 meters), your body has to acclimatize once again. A number of changes take place in the body to allow it to operate with decreased oxygen:
The depth of respiration increases.
• Pressure in pulmonary arteries is increased, "forcing" blood into areas of the lung not normally used during breathing.
• The body produces more red blood cells to carry oxygen.
• The body produces more of a particular enzyme that facilitates the release of oxygen from hemoglobin to the body tissues.
RESOURCE: Oxygen Levels at Different Altitudes (Chart)
How Long Does it Take to Become * FULLY* Acclimatized From Sea Level?
6,000 ft ( 1829 m) — 3 Weeks
• 8,000 ft ( 2438 m) — 4 Weeks
• 10,000 ft ( 3048 m) — 5 Weeks
• 12,000 ft ( 3658 m) — 6 Weeks
• 14,000 ft ( 4267 m) — 7 Weeks
Source: CDC - High Altitude Travel Directory