Altitude Sickness on Himalayan Drives: Prevention, Symptoms, and the Acclimatisation Plan

Acute Mountain Sickness (AMS) is your body protesting low oxygen, and on a Himalayan drive it is the single most likely thing to ruin or end your trip - far more common than a breakdown or a recovery. The core prevention rule is simple and non-negotiable: climb slowly, sleep low, and never gain more than about 500 m of sleeping altitude per day once you are above 3000 m. The honest danger of overlanding is that a vehicle lets you go from 2000 m to 5300 m in a single day, which your lungs were never meant to do. If you fly or drive straight into Leh (3500 m) or Kaza (3650 m), expect a headache by evening; the skill is telling a normal headache apart from the early signs of something that can kill you. This guide gives you the acclimatisation schedule, the symptom ladder, and the one rule that saves lives: if symptoms are worsening, you go down.

At 3500 m there is roughly a third less oxygen in every breath than at sea level; at 5000 m it is around half. Your body adapts by breathing faster and making more red blood cells, but that adaptation takes days, not hours. Trekkers gain altitude on foot and naturally pace themselves. Overlanders do not - a comfortable, heated cabin carries you over a 5000 m pass before your physiology has any clue what happened. That speed of ascent is exactly the risk factor that drives AMS. The danger is not the high pass you cross at noon; it is the altitude you sleep at that night. You can briefly touch Khardung La or Taglang La and descend fine, but choosing to sleep at Pangong (4250 m) on night one out of Leh is how people end up evacuated.

The phrase to burn into memory is climb high, sleep low. Your body tolerates a brief visit to a high altitude far better than a night spent sleeping there, because sleep is when breathing slows and blood oxygen dips lowest - which is exactly why AMS symptoms so often arrive in the small hours and why the sleeping altitude, not the daytime high point, is what determines whether you get sick. This is the single fact that makes a vehicle so deceptively dangerous compared to trekking. A trekker who walks over a 5,000 m pass has spent days climbing to get there and will descend on foot to a lower camp; an overlander can sit in a warm cab, cross Taglang La at 5,328 m at noon feeling fine, and then make the catastrophic choice to push on and sleep high the same night. The cabin hides the ascent rate from your body right up until the moment it cannot cope.

How do you recognise the symptoms before they get dangerous?

Think of it as three rungs on a ladder. Mild AMS is uncomfortable but common. Moderate AMS means you stop ascending. Severe AMS - HACE or HAPE - is a medical emergency where the only treatment is immediate descent. Learn these by heart, because at altitude your own judgement is the first thing to fog over.

• Mild AMS: headache, mild nausea, poor appetite, broken sleep, slight breathlessness on exertion. Rest, hydrate, do not go higher.
• Moderate AMS: a headache that does not respond to paracetamol/ibuprofen, vomiting, dizziness, unusual fatigue. Stop. Descend if no improvement in a few hours.
• HACE (brain): confusion, stumbling, inability to walk a straight line, drowsiness, behaving strangely. This is a kill-or-cure emergency - descend NOW.
• HAPE (lungs): breathlessness at rest, a wet or gurgling cough, frothy or pink sputum, blue lips, tightness in the chest. Descend NOW.
• The clincher test: if a person cannot walk heel-to-toe in a straight line, treat it as HACE until proven otherwise.

The reason we drill the heel-to-toe test into every crew is that the most dangerous symptom of HACE is the one the affected person cannot self-assess: their own judgement. Someone slipping into high-altitude cerebral oedema will often insist they are fine, get irritable when questioned, and want to keep going - which is precisely the brain swelling talking. That is why AMS is a buddy system, not a solo call. On every trip we watch each other, not ourselves, and a simple field check settles arguments: ask the person to walk a straight line heel-to-toe, as if on a tightrope. If they cannot, you treat it as HACE and lose altitude immediately, no discussion, regardless of how strongly they protest. The same goes for HAPE in the lungs - breathlessness at rest, not just on exertion, and a wet or gurgling cough are the red flags, and like HACE the only real treatment is going down.

What does a safe acclimatisation plan look like?

The single best thing you can do is build a graded climb into the itinerary instead of racing for the big-ticket lake on day one. Here is the pattern we run for a Leh-based loop, and the same logic applies to Spiti from the Shimla side rather than the fast Manali side.

• Day 1-2: Arrive Leh (3500 m), do nothing strenuous, sleep two nights at the same altitude. Walk, hydrate, no alcohol.
• Day 3: Short acclimatisation drive (Shanti Stupa, Sangam) and back to Leh to sleep low again.
• Day 4: Nubra via Khardung La - you cross 5350 m but you SLEEP at Hunder (3050 m), which is lower than Leh. Perfect.
• Day 5-6: Pangong via Shyok, sleeping at 4250 m only after several nights of adaptation - not before.
• Approach Spiti from Shimla (Kalpa to Nako to Kaza) rather than the Manali side, so you gain altitude over four days instead of one brutal jump over Kunzum La.
• Golden rule above 3000 m: sleeping altitude up by no more than 500 m per day, and every 1000 m of net gain, take a rest day.

Look at why the Nubra day is the model to copy: you cross Khardung La at about 5,350 m in the middle of the day, banking the climb-high benefit, and then drop to sleep at Hunder around 3,050 m, which is actually lower than Leh. That is climb high, sleep low executed perfectly, and it is why a well-planned Leh loop tackles Nubra before the higher-sleeping Pangong night. Contrast it with the classic mistake of leaving Leh and sleeping at Pangong at 4,250 m on the very first night out, gaining sleeping altitude with no adaptation banked. The Spiti equivalent is identical logic on a bigger scale: approach from Shimla so your sleeping altitudes climb over four days through Kalpa, Nako and Tabo to Kaza, rather than vaulting from Manali over Kunzum La in a single morning. Whether it is a 500 m daily limit or a rest day every 1,000 m of net gain, every rule here exists to slow your sleeping altitude down to the speed your blood can actually keep up with.

Does medication help, and what about oxygen?

Acetazolamide (Diamox) genuinely helps - it speeds acclimatisation and is taken prophylactically, typically starting a day before ascent, but you must talk to a doctor first, especially if you have a sulpha allergy. It makes your fingers tingle and your fizzy drinks taste flat; that is normal. It is an aid, not a force field - Diamox does not let you ignore symptoms or skip the schedule. Dexamethasone is an emergency drug for HACE that buys time for descent, not a preventive you self-prescribe. Carry a portable oxygen cylinder and know that it is a bridge to descent, not a cure; the only real cure for serious AMS is losing altitude. We carry a fingertip pulse oximeter on every trip - a reading that keeps dropping into the low 70s at rest, paired with symptoms, is a strong signal to turn the convoy around.

Read the pulse oximeter correctly, because the number alone can mislead. Oxygen saturation naturally falls with altitude - a reading in the high 80s that would alarm you at sea level can be normal and asymptomatic for an adjusting body at Leh - so it is the trend and the company it keeps that matter, not a single figure. A saturation that keeps sliding into the low 70s at rest over successive checks, in someone who also has a worsening headache or breathlessness, is the combination that tells you to turn around. A one-off low reading in someone who feels fine usually just means check again in a while. We treat the oximeter as one input alongside how the person looks and walks, never as the sole verdict. And we are clear with every crew that oxygen and Diamox are aids that buy time and ease symptoms - they are not permission to keep climbing, and they never replace the schedule or the decision to descend.

Altitude does not care how fit you are or how many trips you have done. I have watched marathon runners get HAPE and chain-smokers walk off a 5000 m pass fine. The mountain only respects one thing - going down. The moment someone is getting worse, we lose altitude. The lake will still be there next year; pretending you are fine is how people do not come back.

When do you abort and descend?

You descend the moment moderate symptoms fail to improve with rest, and you descend instantly for any sign of HACE or HAPE - no waiting for morning, no waiting for the weather, no waiting to see the lake. Even losing 500 to 1000 m of altitude can reverse symptoms dramatically. This is why we plan routes so that a lower camp is always reachable, and why we never put the highest sleeping altitude on the first night. Cold, dehydration and alcohol all make AMS worse, so on a winter overland trip the margins are thinner still. The brave decision in the mountains is almost always the one to turn around.

Plan the descent before you ever need it, because a person with HACE at 2 am is not someone you want to be route-finding for in the dark. We build every itinerary so a lower camp is reachable from each night's stop, which means we always know which way is down and roughly how long it takes. That single piece of forethought is what turns an emergency into a manageable drive. It is also why winter trips demand even wider margins: cold, the relentless dehydration of dry high-altitude air, and any alcohol all stack the odds toward AMS, and a -20C night gives you far less room for error than a summer one. None of the gear changes the core rule. A heater, oxygen and Diamox make a high camp more bearable, but if someone is getting worse, the answer is not more equipment - it is altitude lost, tonight, in whichever direction is down.

Frequently Asked Questions

How fit do I need to be to avoid altitude sickness?

Fitness barely correlates with AMS. Very fit people sometimes ascend too fast precisely because they feel strong. Susceptibility is largely individual and partly genetic; the only reliable protection is a slow, graded climb with sleeping altitude rising no more than about 500 m per day above 3000 m.

Can children and older adults handle Ladakh altitude?

Healthy older adults often do fine with extra acclimatisation days. Young children are harder to assess because they cannot describe symptoms well, so paediatric advice and extra caution are essential, and infants are best kept off the highest routes.

Is it safe to drink alcohol at altitude?

No. Alcohol depresses breathing, worsens dehydration, and masks early AMS symptoms. Skip it entirely until you are well acclimatised and back down at moderate altitude.

How much water should I drink?

Aim for three to four litres a day at altitude. The dry, cold air strips moisture fast, and dehydration mimics and worsens AMS. Clear, pale urine is your simplest field gauge.

Does a pulse oximeter reading tell me if I have AMS?

Not on its own. Oxygen saturation naturally falls with altitude, so a reading that looks low at sea level can be normal at Leh. What matters is the trend paired with symptoms: a saturation sliding into the low 70s at rest over repeated checks, alongside a worsening headache or breathlessness, is the signal to descend. Treat the oximeter as one input, never the sole verdict.