Altitude Illness

Last Updated: July 30, 2018
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​At altitude, there is decreased availability of oxygen in ambient (surrounding) air. This lowers the oxygen supply to the body, which can lead to altitude illnesses and reduced physical and mental performance. Altitude exposure may also increase the likelihood of other environmental injuries (e.g., cold injuries) or worsen pre-existing medical conditions.

​Altitude​Meters (m) / Feet (ft)​Effects of Acute Altitude Exposure
LowSea Level - 1200m / 4000 ftNone
Moderate1200-2400m / 4000-7870 ftMild altitude illness and decreased performance may occur
High2400-4000m / 7870-13,125 ftAltitude illness and performance decrements are more common and greater
Very High4000-5500m / 13,125-18,000 ftAltitude illness and decreased performance is the rule
Extreme5500m / 18,000 ft - and higherWith acclimatization, humans can function for short periods of time