Altitude Sickness on Himalayan Treks: Signs, Prevention and What to Do
How acute mountain sickness shows up, why going slow matters more than fitness, and the simple checks good trek leaders run every morning and evening.
28 September 2026 · 5 min read
Above about 2,500 metres there's less oxygen in every breath, and your body needs a day or two to adjust. Most Himalayan treks — Kedarkantha (3,810 m), Hampta Pass (about 4,270 m), Bhrigu Lake (about 4,300 m) — go well above that. Acute mountain sickness (AMS) is common, usually mild, and almost always avoidable if you respect a few rules.
This is general guidance, not medical advice. Talk to a doctor before a high-altitude trek, especially if you have a heart, lung or blood-pressure condition.
The early signs
- Headache that doesn't go away with rest and water
- Loss of appetite or nausea
- Unusual tiredness or weakness
- Dizziness or trouble sleeping
These feel a lot like a hangover or a bad cold. The mistake people make is hiding them to keep up with the group.
The warning signs — descend
- Breathlessness even when resting
- A wet, persistent cough
- Confusion, clumsiness or trouble walking in a straight line
- Extreme drowsiness
These can mean fluid on the lungs (HAPE) or brain (HACE), which are emergencies. The treatment is to go down — even 300–500 metres helps — with oxygen if it's available.
How to prevent it
- Go slow. Walk at a pace where you can still talk.
- Drink 3–4 litres of water a day at altitude.
- Don't gain too much sleeping height in one day once you're above 3,000 m.
- Skip alcohol and smoking on the trek.
- Eat even when you're not hungry — your body needs the fuel.
- Tell your trek leader about any symptom, however small.
What a good trek leader does
On Deshraah treks the leader checks everyone's oxygen level and pulse with a pulse oximeter every morning and evening, carries an oxygen cylinder and a first-aid kit, and turns a person or the whole group back if the numbers or symptoms say so. A summit is never worth a rescue.
Choosing your first high trek
If it's your first time above 3,000 m, start with a trek that climbs gradually and has an easy way down — Nag Tibba, Dayara Bugyal or Kedarkantha are good first treks. Save passes above 4,000 m, like Hampta or Indrahar, for after you've done one.