Altitude Sickness on Nepal Treks: Symptoms, Prevention & Staying Safe

Altitude is the real challenge on Nepal's big treks. Here's how to ascend safely and enjoy the mountains.

On treks like Everest Base Camp, the Annapurna Circuit and Manaslu, the biggest risk isn't the steepness — it's the altitude. Acute Mountain Sickness (AMS) can affect anyone, regardless of age or fitness, when they climb too high too fast. The good news: it is largely preventable with the right pace and habits. Here is what every trekker should know.

What is altitude sickness?

As you climb, the air holds less oxygen. Above roughly 2,500–3,000 m your body needs time to adapt. If you ascend faster than it can adjust, fluid balance shifts and AMS develops. Mild AMS is common and manageable; the danger is ignoring it and continuing to climb, which can lead to the serious conditions HAPE (lungs) and HACE (brain).

Symptoms to watch for

• Headache that doesn't ease with rest or water
• Nausea or loss of appetite
• Dizziness or unusual fatigue
• Difficulty sleeping
• Shortness of breath at rest (serious — descend)

How to prevent it

Prevention comes down to a few simple, proven rules. Ascend gradually, build in acclimatisation days, and follow the climber's maxim of 'climb high, sleep low'. Drink plenty of water, eat well even when your appetite drops, avoid alcohol at altitude, and never rush to make up a schedule. A good itinerary is designed around acclimatisation, not against it.

• Don't gain more than ~500 m sleeping elevation per day above 3,000 m
• Take scheduled rest days (e.g. Namche, Dingboche on EBC)
• Hydrate — aim for 3–4 litres of water a day
• Walk at a steady, conversational pace
• Tell your guide early if you feel unwell

What to do if it happens

Mild symptoms usually settle with rest, fluids and not going higher until you feel better. If symptoms are moderate or worsening, the only reliable treatment is to descend. This is exactly why trekking with a trained local guide matters: our guides monitor the whole group, carry an oximeter, and know the safe descent points on every route. Travel insurance that covers high-altitude evacuation is essential.