Risk categories	Description
Low	Individuals with no prior history of altitude illness and ascending to ≤ 2800 m (˜ 9200 feet).
Low	Individuals taking ≥ 2 days to arrive at 2500 m to 3000 m (˜ 8200 to ˜ 9850 feet) with subsequent increases in sleeping elevation < 500 m by day/˜ 1650 feet by day.
Moderate	Individuals with prior history of AMS and ascending to 2500m to 2800 m (˜ 8200 to ˜ 9200 feet) in 1 day.
Moderate	No history of AMS and ascending to > 2800 m (˜ 9200 feet) in 1 day
Moderate	All individuals ascending > 500 m/d (˜ 1650 feet) (increase in sleeping elevation) at altitudes above 3000 m/˜ 9850 feet.
High	History of AMS and ascending to ≥ 2800 m/˜ 9200 feet in 1 day
High	All individuals with a prior history of HAPE or HACE.
High	All individuals ascending to > 3500 m/˜ 11,500 feet in 1 day.
High	All individuals ascending > 500 m/d (˜ 1650 feet/d) increase in sleeping elevation above > 3500 m/˜ 11,500 feet.
High	Very rapid ascents (e.g. Mt Kilimanjaro).