Altitude sickness in the Himalaya, explained simply
· 7 min read
Most people who visit Ladakh, Spiti or the Everest region feel the altitude at some point. A mild headache on the first evening in Leh is normal. What matters is knowing why it happens, how to make it less likely, and when a symptom means you should stop climbing.
This is general information, not medical advice. Speak to your doctor before any trip above 3,000 metres, especially if you have heart or lung conditions, high blood pressure or are pregnant.
What altitude sickness is
As you go higher, each breath carries less oxygen. At Leh, about 3,500 metres up, there is roughly a third less oxygen in every breath than at sea level. Your body adapts by breathing faster and, over a few days, by making changes to your blood. Acute mountain sickness, or AMS, is what happens when you climb faster than your body can adjust.
It usually starts six to twelve hours after arriving at a new height, most often above 2,500 metres. Fitness does not protect you; fit young people often climb too fast and suffer for it.
The symptoms
- A headache, often the first sign
- Loss of appetite or nausea
- Tiredness and weakness
- Dizziness
- Poor, broken sleep
Mild AMS usually settles with rest at the same height within a day or two. Two rarer conditions are emergencies: HAPE, fluid on the lungs, which causes breathlessness at rest, a persistent cough and blue lips; and HACE, swelling of the brain, which causes confusion, clumsiness and severe drowsiness. Both need immediate descent and medical help.
How to prevent it
Go up slowly
Above 3,000 metres, try not to raise the height you sleep at by more than 300 to 500 metres a day, and take a rest day every three or four days. You can climb higher during the day and come back down to sleep. That is why our Ladakh journeys spend three nights in Leh before crossing Khardung La, and why the Everest Base Camp trek has two rest days built in.
Rest when you fly in
Flying to Leh takes you from near sea level to 3,500 metres in about an hour. Spend the first 24 to 48 hours resting: a short walk, plenty of tea and an early night. Going sightseeing on day one is the most common mistake we see.
Drink, eat and avoid alcohol
Drink three to four litres of water a day, eat regular carbohydrate-rich meals, and skip alcohol and sleeping pills for the first two days at altitude.
Ask your doctor about medication
Acetazolamide, often sold as Diamox, can help some travellers acclimatise. It is a prescription medicine with side effects, so only take it on a doctor’s advice.
What to do if you feel unwell
- Tell your guide or trip leader straight away. It is never an inconvenience.
- Do not go any higher until the symptoms have gone.
- Rest, drink water and take simple painkillers for a headache if they help.
- If you feel worse, or have any sign of HAPE or HACE, go down at once. Even 300 to 500 metres makes a difference.
On our road trips every vehicle carries an oxygen cylinder and a pulse oximeter, and our itineraries keep a lower place to sleep within reach. Oxygen buys time, but descending is the real treatment.
Children and older travellers
Children can get AMS too and may not explain how they feel, so watch for irritability, poor sleep and loss of appetite. We do not recommend that children under five sleep at 4,000 metres or above. Older travellers do well with a slower pace and an extra rest day; talk to your doctor first.
Insurance
For any high trek, and for Nepal in particular, buy travel insurance that covers trekking at the heights you will reach and includes helicopter evacuation.
