Altitude Sickness
Also known as: Acute mountain sickness, AMS, Soroche, High altitude illness, HACE, HAPE
Altitude sickness is a group of symptoms caused by reduced oxygen at high elevations, typically above 2,500m.
Last updated: 2 April 2026
Real-world example
You fly directly from sea level to Cusco, Peru (3,400m). Within 6 hours you have a splitting headache, nausea, and can barely walk up a flight of stairs. Your hotel gives you coca tea and advises rest. After 36 hours of acclimatisation, the symptoms ease. If you'd flown to Lima first and taken the bus up gradually, the adjustment would have been far less severe.
Why travellers need to know
Altitude sickness is entirely predictable and largely preventable, yet it catches thousands of travellers every year because they underestimate how quickly symptoms develop. It affects fit and unfit people equally. The only reliable prevention is gradual ascent. Popular destinations at altitude include Cusco (3,400m), La Paz (3,640m), Lhasa (3,650m), and Kilimanjaro summit (5,895m). Pre-existing heart or lung conditions increase risk significantly.
Country-specific notes
Cusco sits at 3,400m; most visitors feel symptoms
Most travellers flying directly to Cusco from sea level experience some altitude symptoms. Hotels and restaurants routinely offer coca tea (mate de coca). Pharmacies sell acetazolamide (Diamox) over the counter. The Sacred Valley (2,800m) is a lower-altitude alternative for the first night.
Tip
Spend your first night in the Sacred Valley (Ollantaytambo or Urubamba) at 2,800m before moving up to Cusco. This single step reduces symptoms significantly.
Frequently asked questions
How Nomedic helps
Your Nomedic record flags any heart or lung conditions that increase altitude risk, so a trekking doctor can assess you accurately at altitude.
Sources
Your health records, anywhere you go
Your health conditions, visible when altitude matters.
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