Understanding altitude sickness

Above roughly 2,500m, the air holds progressively less oxygen, and your body needs time to adapt. Acute Mountain Sickness (AMS), which brings headache, nausea, fatigue and poor sleep, is common and usually manageable; the serious complications (HAPE and HACE) are rare when a sensible itinerary is followed, but they're the reason every reputable operator builds in rest days rather than racing to altitude.

The golden rule is simple: climb high, sleep low where possible, and never ascend more than about 300–500m in sleeping altitude per day above 3,000m, with a full rest/acclimatisation day roughly every 3–4 days. Every itinerary we run is built around this pattern, including the well-known rest days at Namche Bazaar and Dingboche on the Everest route.

Hydration matters more than most people expect (3-4 litres a day), and it's worth avoiding alcohol and sleeping pills at altitude, since both can mask or worsen symptoms. Your guide will check in daily and carries a pulse oximeter to track your blood oxygen saturation; a dropping trend is the earliest and most reliable warning sign, well before you'd feel seriously unwell.

The single most important thing to know: mild AMS symptoms are common and not a reason to panic, but they are always a reason to tell your guide immediately. The only real treatment that matters if symptoms worsen is descent, and it works fast: most people feel dramatically better within a few hundred metres of losing altitude.