Altitude sickness (or Acute Mountain Sickness) is a condition caused by ascending too quickly and not allowing the body time to adjust to the reduced oxygen and changes in air pressure. This causes hypobaric hypoxia: a lack of oxygen reaching your body’s tissue. Symptoms typically begin to show above 2,500m if a person has not allowed their body time to adjust to the change in altitude. Symptoms of mild altitude sickness include dizziness, fatigue, headaches, nausea and vomiting, loss of appetite, a rapid pulse, and/or shortness of breath. More serious symptoms can include chest tightness, confusion, coughing, social withdrawal, trouble maintaining consciousness, a change in complexion or skin colour, difficulties walking, and eventually the risk of coma or death.
While it certainly helps to be in good physical shape, the ability to adjust quickly to the changing oxygen levels is largely genetic. It is impossible to tell how well any one climber will fare in an oxygen deprived environment until they are actually in that environment. With the exception of going and staying in high altitude areas, the best option is to consider using a high altitude training system to simulate high altitude environments and induce beneficial adaptations.
Read more information & Action Guide to High Altitude and consult your physician if required.