Altitude Sickness on Nepal Treks
Altitude sickness is the most important health topic on any high trek in Nepal. It can affect anyone, no matter how fit or young you are, but the good news is that it’s largely preventable with a sensible itinerary and by listening to your body. This guide explains what happens at altitude, the warning signs, and the simple rules that keep trekkers safe.
This is general information, not medical advice. Talk to your doctor or a travel clinic before a high-altitude trek, especially if you have a medical condition or want to take altitude medication.
What is altitude sickness?
As you climb higher, the air pressure drops and each breath contains less oxygen. Your body can adapt to this (that’s acclimatisation), but it needs time. If you climb faster than your body can adjust, you can develop Acute Mountain Sickness (AMS). Symptoms often start above about 2,500–3,000 m.
How high do the treks go?
| Trek | Highest point | Highest night (typical) |
|---|---|---|
| Ghorepani Poon Hill | 3,210 m | ~2,860 m |
| Langtang Valley | 4,984 m (optional hike) | ~3,870 m |
| Annapurna Base Camp | 4,130 m | 4,130 m |
| Mardi Himal | 4,500 m (day hike) | ~3,580 m |
| Gokyo Lakes | 5,357 m | ~4,790 m |
| Everest Base Camp | 5,545 m | ~5,164 m |
| Annapurna Circuit | 5,416 m | ~4,450 m |
Symptoms to watch for
Mild AMS feels a bit like a hangover:
- Headache (the most common sign)
- Loss of appetite or nausea
- Tiredness and weakness
- Dizziness
- Difficulty sleeping
Mild symptoms are common and usually improve with rest at the same altitude. Do not go higher until they’ve gone.
Serious warning signs: descend immediately
Two rare but dangerous forms of altitude illness need urgent action:
- HACE (fluid on the brain): confusion, loss of coordination (stumbling, can’t walk in a straight line), severe headache that doesn’t improve, unusual drowsiness or behaviour
- HAPE (fluid on the lungs): breathlessness even at rest, a persistent cough (sometimes with frothy or pink sputum), chest tightness, extreme tiredness
If you see these signs, descend straight away, even at night, and get medical help. Descending just a few hundred metres often makes a big difference.
How to prevent altitude sickness
- Go up slowly. Above about 3,000 m, try not to increase your sleeping altitude by more than roughly 300–500 m per day.
- Take acclimatisation days. Plan a rest day every 3–4 days, or for every 1,000 m gained. On my Everest Base Camp itinerary we rest in Namche and Dingboche.
- Climb high, sleep low. Short hikes higher than where you’ll sleep help your body adapt.
- Drink plenty of water, around 3–4 litres a day, and eat well even if your appetite drops.
- Avoid alcohol and sleeping pills at altitude.
- Walk slowly. You should be able to talk comfortably while walking. “Bistari, bistari” (slowly, slowly) is the golden rule on Nepal’s trails.
- Be honest about how you feel. Tell your guide about any symptoms early, however mild.
What about altitude medication?
Some trekkers use acetazolamide (often sold as Diamox) to help prevent AMS. It isn’t suitable for everyone and has side effects, so only use it after speaking to a doctor. Medication is never a replacement for a slow ascent.
Travel insurance
Make sure your travel insurance covers trekking at the altitude you’re going to (for example up to 6,000 m for Everest Base Camp) and helicopter evacuation. Check the policy carefully before you book.
How I keep you safe
On every trek I plan a realistic pace with built-in acclimatisation, check in with you every day about how you’re feeling, and adjust the plan if needed. A day of rest or turning back early is always better than pushing on. The mountains will still be there.
Planning a high trek? Send me a message and I’ll suggest an itinerary with the right acclimatisation for you.
