Altitude Sickness on Nepal Treks: Prevention, Symptoms and What We Do About It

Nothing on a Himalayan trek matters more than this topic, so we will be direct, the way we are at our pre-trek briefings. Altitude sickness is common, usually mild, occasionally dangerous, and overwhelmingly preventable with patience and honesty.

What altitude actually does

Above roughly 2,500 m the air holds progressively less oxygen, and your body needs days, not hours, to adapt. Push higher faster than it can adjust and you get Acute Mountain Sickness (AMS): headache, nausea, poor appetite, unusual fatigue, broken sleep. Fitness does not protect you; marathon runners get AMS while grandmothers stroll past them. Rate of ascent is almost everything.

The rules that keep you safe

• Climb high, sleep low. Day hikes above your sleeping altitude speed adaptation. It is why our itineraries include "rest" days that are not really rest.
• Above 3,000 m, limit sleeping-altitude gains to roughly 300–500 m a day, with a full acclimatisation day every 1,000 m or so.
• Drink constantly. 3–4 litres a day. Dehydration mimics and worsens AMS.
• Eat, even when appetite fades. Carbs are fuel for adaptation (see: dal bhat).
• No alcohol and no sleeping pills at altitude, both suppress the night-time breathing your body relies on.
• Tell your guide everything. A headache reported at dinner is a plan; a headache hidden until midnight is an emergency.

When symptoms appear

Mild AMS. A headache that eases with fluids, rest and basic painkillers, means stop ascending and stay at the same sleeping altitude until it clears. Worsening symptoms mean descend, immediately, whatever the itinerary says. The serious forms, HAPE (fluid in the lungs: breathlessness at rest, wet cough) and HACE (fluid around the brain: confusion, stumbling like intoxication), are emergencies where descent and evacuation come before everything else. This is why insurance with helicopter cover is mandatory on our treks.

What our guides do on every departure

Itineraries built to the ascent rules above; a pulse oximeter and evening check-ins for every guest above 3,500 m; guides trained to recognise AMS early and empowered to change the plan without penalty to you; first aid kits on every trek; and a 24/7 Kathmandu coordinator who can trigger an evacuation within minutes. In years of high treks, EBC, Thorong La, Larkya Lathis protocol has kept our record where we intend it to stay.

This article is general information from our field experience, not personal medical advice, talk to a travel-medicine professional about your own health before trekking, especially regarding preventive medication.