Travellers whose itineraries will take them above an altitude of 1,829-2,438m (6,000-8,000ft) should be aware of the risk of altitude sickness. Travellers are exposed to higher altitudes in a number of ways: by flying into a high-altitude city, by driving to a high-altitude destination, or by hiking or climbing in high mountains.
Travellers vary considerably in their susceptibility to altitude sickness, and no screening tests are available to predict someone's risk for altitude isickness.
Susceptibility to altitude sickness appears to be inherent in some way and is not affected by training or physical fitness.
How a traveller has responded in the past to exposure to high altitude is the most reliable guide for future trips but is not infallible.