Every season, hospitals in Leh treat travellers who flew in from the plains, felt fine at the airport, and went sightseeing the same afternoon. By night they had a pounding headache, nausea, and breathlessness. Some needed oxygen; a few needed evacuation. High-altitude sickness does not care how fit you are. It cares how fast you climbed.
The Indian Army manages this risk every day at posts from Ladakh to Arunachal, and its acclimatisation discipline is the best model any traveller can follow.
What happens to the body at altitude
Above roughly 2,500 metres, each breath carries noticeably less oxygen. Leh sits at about 3,500 metres, Kaza in Spiti at about 3,800, and Gurudongmar Lake in North Sikkim above 5,000. The body can adapt, by breathing faster and producing more red blood cells, but that takes days. Climb faster than you adapt, and illness follows.
The three conditions to know
1. Acute Mountain Sickness (AMS). The common form. Headache plus one or more of nausea, loss of appetite, fatigue, dizziness, or poor sleep, usually 6 to 12 hours after arrival. Mild AMS settles with rest and no further ascent.
2. High-Altitude Pulmonary Oedema (HAPE). Fluid in the lungs. Warning signs: breathlessness even at rest, a persistent cough (sometimes with pink frothy sputum), chest tightness, and unusual weakness. This is an emergency.
3. High-Altitude Cerebral Oedema (HACE). Swelling of the brain. Warning signs: confusion, unsteady walking like being drunk, severe headache unrelieved by medication, and drowsiness. This is an emergency.
With HAPE or HACE, the treatment is to descend immediately, even at night, and get oxygen and medical care. Waiting to see if it improves is how people die.
The acclimatisation rules
- Rest completely for the first 24 to 48 hours after flying into Leh. No sightseeing, no Khardung La on day one. Troops posted to high altitude follow a mandatory staged acclimatisation schedule for this reason.
- Climb gradually above 3,000 metres: raise your sleeping altitude by no more than 300 to 500 metres a day, with a rest day every three to four days.
- Climb high, sleep low. Day trips to higher passes are fine once acclimatised, as long as you return lower to sleep.
- Drink enough water, but do not overdo it; dehydration mimics and worsens AMS.
- Avoid alcohol and sleeping pills for the first few days. Both suppress breathing.
- Travelling by road from Manali or Srinagar allows gradual acclimatisation and is gentler than flying straight to Leh.
About preventive medication
Acetazolamide is widely used to help prevent AMS in people making rapid ascents, and to treat mild cases. It is a prescription medicine with side effects and people it is unsuitable for, including those with a sulfa allergy. Discuss it with a doctor before your trip rather than buying it at a pharmacy in Leh. No tablet replaces proper acclimatisation.
Who should get medical advice before going
Anyone with heart disease, lung disease including asthma or COPD, severe anaemia, poorly controlled blood pressure, pregnancy, or a previous episode of HAPE or HACE should consult a doctor before travelling to high altitude.
The golden rule
If you feel unwell at altitude, assume it is altitude sickness until proven otherwise. Never climb higher with symptoms. If symptoms get worse despite rest, go down.
This article is for general information only and is not a substitute for professional medical advice. Consult a doctor before high-altitude travel, especially if you have a medical condition.
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