Every year, approximately 30% of trekkers ascending rapidly to 3,500m+ develop symptoms of acute mountain sickness. Most cases resolve with rest and slower ascent. A small minority — roughly 1% — develop life-threatening High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE). The protocol below prevents nearly all of them.
Why Altitude Makes You Sick (And Why That Is Fixable)
At 4,000m, there is roughly 40% less oxygen in the air than at sea level. Your body adapts — it produces more red blood cells, breathes faster at rest, and changes how it metabolises food. These adaptations take 4–6 days. The error most trekkers make is ascending faster than the body can adapt.
The threshold for symptoms is around 2,500m for sensitive individuals and 3,500m for most healthy adults. Below 2,500m, symptoms are rare. Above 4,500m, the protocol becomes non-negotiable.
The 7-Day Acclimatization Protocol
This is the schedule we use on every InstaHimalayas expedition above 3,500m. The rule is: sleep low, climb high. Day-hike high, sleep at a lower elevation.
- Day 1: Arrive in Manali (2,050m) or equivalent staging town. Rest. Hydrate aggressively — 4–5 litres of water across the day. No alcohol.
- Day 2: Easy activity day in the staging town. Walk 6–8km on flat terrain. Eat light. Sleep by 9pm.
- Day 3: Drive or trek to mid-elevation (2,800–3,200m) — Kaza, Jibhi, or Sangla. Sleep here. Mild headache is normal; treat with paracetamol, not Diamox yet.
- Day 4: Active rest. Hike to 3,500m, return to sleep at 3,200m. This is the climb-high, sleep-low principle in action.
- Day 5: Move up to 3,800–4,000m. Symptoms often peak here. Rest day. If headache is severe, do not ascend — descend 500m instead.
- Day 6: Move up to 4,000–4,500m. Most trekkers feel significantly better by now. The body has adapted.
- Day 7: First summit attempt or high pass crossing is safe. Many trekkers who skip days 1–4 will feel ill on day 7 instead. The protocol is your insurance.
Symptom Recognition: When to Worry
AMS is graded by severity. Knowing which level you are at tells you what action to take.
Mild AMS
Headache, fatigue, loss of appetite, mild nausea, disturbed sleep. Treatment: stop ascending, rest 24 hours, hydrate, take ibuprofen or paracetamol. Most cases resolve in 24–48 hours.
Moderate AMS
Severe headache that does not respond to painkillers, persistent vomiting, severe fatigue, difficulty walking in a straight line. Treatment: descend immediately, minimum 500m. Do not push through. Diamox (acetazolamide) 250mg twice daily can help — start it now if you have not already.
Severe AMS (HAPE / HACE)
HAPE: shortness of breath at rest, pink frothy sputum, blue lips. HACE: confusion, stumbling, loss of coordination. Treatment: immediate descent is the only definitive treatment. This is a medical emergency. Administer oxygen if available. Dexamethasone 8mg loading dose for HACE. Nifedipine 30mg slow-release for HAPE. Evacuate to a hospital below 2,500m.
Drugs That Actually Help (And The Ones That Don't)
Diamox (acetazolamide): Effective. Prevents AMS in 75% of cases when started 24 hours before ascent. Side effect: tingling in fingers and toes, increased urination, altered taste of carbonated drinks. Standard protocol is 125mg twice daily starting the day before you cross 3,000m, continuing until 2 days after reaching your highest sleep altitude.
Dexamethasone: Reserved for HACE rescue. Not for prevention — it masks symptoms rather than addressing the cause.
Nifedipine: Reserved for HAPE rescue. Not for prevention.
Ginkgo biloba: The evidence is mixed and inconclusive. Not part of our protocol.
Coca tea: A traditional Andean remedy with mild acclimatisation benefits and significant psychological comfort. Not a substitute for the protocol above, but harmless as a supplement.
Hydration: The Quiet Hero
Dehydration mimics and worsens AMS. At altitude you lose water through faster breathing (the cold, dry air you exhale carries moisture out). The rule: drink until your urine is clear and frequent. That is 4–5 litres per day above 3,500m for most adults. Carry a water filter or purification tablets — boiling above 4,000m is energy-expensive.
What Our Guides Actually Do
Every InstaHimalayas expedition above 3,500m carries a portable pulse oximeter. We measure every guest's oxygen saturation and heart rate twice daily during acclimatisation. A rising heart rate at the same elevation is one of the earliest signs of inadequate acclimatisation — sometimes appearing 12–24 hours before symptoms. We use this as a leading indicator to catch problems before they become clinical.
Our guides are certified in Wilderness First Aid and High Altitude Medicine. Every expedition has a satellite communicator (Garmin inReach) for evacuation coordination. We take this seriously because the mountains take altitude seriously.
Ready to plan a trek that respects the protocol from day one? Start planning with InstaHimalayas — our itineraries are built around the climb-high, sleep-low principle from the ground up.
