Altitude sickness prevention for Indian trekkers — a practical guide
By Diya Verma (Karthik Raghavan is a trekking guide turned travel journalist with over 200 high-altitude treks across the Himalayas, East Africa and South America. He writes about adventure logistics, fitness preparation and budget planning for Indian outdoor enthusiasts.) · Published · 10 min read
Altitude sickness is the biggest health risk on high-altitude treks and it does not care how fit you are. Here is the practical prevention and management guide every Indian trekker needs.
Quick answer
Altitude sickness (Acute Mountain Sickness, or AMS) affects most people above 2,500 metres and can become life-threatening above 4,000 metres. The only reliable prevention is gradual ascent — gain no more than 300 to 500 metres of sleeping altitude per day above 3,000 metres, and take a rest day every 3 to 4 days of climbing. Diamox (acetazolamide) helps with acclimatisation but is not a substitute for ascending slowly. Fitness level does not protect against AMS — fit, young trekkers are just as susceptible as unfit ones. The golden rule: if symptoms worsen, descend immediately.
What altitude sickness actually is
At high altitude, the air pressure is lower and each breath contains fewer oxygen molecules. Your body needs time to adjust — producing more red blood cells, increasing breathing rate, and making other physiological adaptations. When you ascend faster than your body can adapt, you get altitude sickness.
There are three forms of increasing severity:
- Acute Mountain Sickness (AMS): headache, nausea, fatigue, dizziness, poor appetite, difficulty sleeping. Unpleasant but not immediately dangerous. Affects 40 to 70 percent of trekkers at 4,000+ metres.
- High Altitude Cerebral Edema (HACE): swelling of the brain. Symptoms include confusion, loss of coordination (ataxia), irrational behaviour, severe headache. Life-threatening — requires immediate descent.
- High Altitude Pulmonary Edema (HAPE): fluid in the lungs. Symptoms include breathlessness at rest, persistent cough (sometimes with pink frothy sputum), extreme fatigue, chest tightness. Life-threatening — requires immediate descent and supplemental oxygen.
HACE and HAPE can develop from mild AMS within hours. They are medical emergencies. The only definitive treatment for both is descent.
The acclimatisation protocol
Proper acclimatisation is the single most effective prevention against altitude sickness. The evidence-based guidelines are:
- Above 3,000 metres, increase your sleeping altitude by no more than 300 to 500 metres per day.
- Take a rest day (no altitude gain) every 3 to 4 days of ascent.
- Climb high, sleep low: you can climb to a higher elevation during the day as long as you descend to a lower camp to sleep. This accelerates acclimatisation.
- Hydrate: drink 3 to 4 litres of water per day at altitude. Dehydration mimics and worsens AMS symptoms.
- Avoid alcohol and sedatives for the first 48 hours at altitude — they suppress breathing and impair acclimatisation.
On popular treks like Everest Base Camp and Kilimanjaro, the standard itinerary builds in rest days. Do not skip them to save time. On Indian Himalayan treks (Ladakh, Spiti, Roopkund), many itineraries are poorly designed for acclimatisation — if you fly into Leh (3,500m), spend at least 2 full rest days before any trekking or strenuous activity.
Diamox (acetazolamide) — what Indian trekkers should know
Diamox is a carbonic anhydrase inhibitor that accelerates acclimatisation by increasing your breathing rate and promoting bicarbonate excretion through the kidneys. It is widely used by trekkers, mountaineers and the military for altitude sickness prevention.
Standard prophylactic dose: 125 mg twice daily, starting 1 to 2 days before ascent and continuing for 2 to 3 days after reaching maximum altitude. Diamox is a prescription medication in India — consult a doctor before taking it. Common side effects include tingling in fingers and toes (paraesthesia), increased urination, and a metallic taste with carbonated drinks. These are annoying but not dangerous.
Important caveats:
- Diamox is NOT a cure for altitude sickness. It aids acclimatisation but does not prevent it if you ascend too fast.
- People with sulfa allergies should not take Diamox.
- Diamox can mask early AMS symptoms — this is dangerous because it may delay the decision to descend. Monitor yourself honestly even while taking it.
- Some trekkers prefer to carry Diamox as a treatment option rather than taking it prophylactically. This is a valid approach — discuss with your doctor.
Why fitness does not protect you
This is counterintuitive but well-established: physical fitness does not reduce your risk of altitude sickness. Fit, young trekkers are sometimes more susceptible because they ascend too fast (their fitness allows them to climb quickly, which outpaces acclimatisation), they underestimate the altitude risk (they are used to their body performing well), and they are less likely to acknowledge symptoms and rest.
Conversely, older, moderately fit trekkers who pace themselves carefully, hydrate well and take rest days often acclimatise better because they are not pushing the pace. The lesson: respect the altitude regardless of your fitness level. Climb slowly, listen to your body, and do not let ego drive your ascent rate.
Previous altitude experience helps somewhat — if you have been to 4,000+ metres before and acclimatised well, you may acclimatise faster the next time. But this is not guaranteed, and each trip is different.
Emergency protocols and when to descend
Descend immediately if:
- Your headache does not respond to paracetamol and rest after 12 to 24 hours
- You develop ataxia (cannot walk a straight line, stumbling, loss of coordination)
- You become confused or irrational
- You develop breathlessness at rest or a persistent wet cough
- Your condition worsens despite no further altitude gain
Descend at least 300 to 500 metres, ideally 1,000 metres or more. HACE and HAPE typically improve rapidly with even modest descent. If supplemental oxygen is available (carried by guides on Kilimanjaro and some Himalayan treks), use it while descending.
Dexamethasone (4mg every 6 hours) is used as an emergency treatment for HACE; nifedipine (20mg slow-release every 8 hours) for HAPE. These are prescription medications and should only be used in genuine emergencies — carry them if your doctor prescribes them, but descent remains the primary treatment.
Before any high-altitude trek, ensure your travel insurance covers helicopter evacuation and that your trekking operator has a clear emergency protocol including radio communication and evacuation contacts.
Frequently asked questions
Can altitude sickness be fatal?
Yes. HACE and HAPE are life-threatening if untreated. Deaths occur every year on high-altitude treks globally, including in Nepal and on Kilimanjaro. The vast majority are preventable with proper acclimatisation and timely descent.
Should I take Diamox on the Everest Base Camp trek?
Many EBC trekkers use Diamox prophylactically and find it helpful. Consult your doctor before the trek. The standard EBC itinerary builds in acclimatisation days, which is the primary prevention — Diamox is an aid, not a replacement for proper pacing.
Can I fly directly to Leh and start trekking?
No. Leh is at 3,500m and you will feel the altitude immediately after flying from a low-elevation Indian city. Spend at least 2 full rest days in Leh before any strenuous activity. Walk gently on day 1, hydrate heavily, and do not climb stairs or carry heavy bags on arrival day.