Understanding Altitude and Oxygen Levels
At sea level, the air contains about 21% oxygen at a pressure of 101 kPa. At 3,500 metres (Kedarnath's altitude), oxygen partial pressure drops to approximately 65 kPa — meaning your lungs must work significantly harder to absorb the same amount of oxygen. At 4,329 metres (Hemkund Sahib), the effective oxygen is roughly 57% of sea level.
The body can adapt to altitude, but it takes time. When you ascend faster than your body can acclimatise, Acute Mountain Sickness (AMS) develops. It affects approximately 25–40% of people ascending to 3,500m without proper acclimatisation.
AMS Symptoms — Know the Warning Signs
Mild AMS (Stay and Monitor)
- Headache — the hallmark symptom
- Fatigue and weakness
- Loss of appetite
- Nausea
- Dizziness
- Poor sleep
Moderate AMS (Stop Ascending, Consider Descent)
- Severe, persistent headache unresponsive to paracetamol
- Vomiting
- Extreme fatigue — difficulty walking
- Shortness of breath at rest
Severe AMS — HACE/HAPE (Descend Immediately, Life-Threatening)
- HACE (High Altitude Cerebral Edema) — confusion, loss of coordination, inability to walk in a straight line. Descend immediately and call emergency services.
- HAPE (High Altitude Pulmonary Edema) — severe breathlessness at rest, coughing (may produce pink frothy mucus), blue lips or fingernails. Descend immediately. Administer supplemental oxygen if available.
The Golden Rules of Acclimatisation
- Ascend gradually — above 3,000m, limit daily altitude gain to 300–500m of sleeping altitude
- Climb high, sleep low — you can ascend higher during the day if you return to lower altitude to sleep
- One rest day for every 1,000m gain above 3,000m
- Stay hydrated — drink 3–4 litres of water per day at altitude
- Avoid alcohol for the first 48 hours at altitude — it suppresses respiration during sleep
- Avoid sleeping pills (they suppress breathing)
Diamox (Acetazolamide) — Should You Take It?
Diamox (Acetazolamide 250mg) is a carbonic anhydrase inhibitor that accelerates acclimatisation by stimulating breathing. It is the most evidence-based medication for AMS prevention.
- Dosage: 125–250mg twice daily, starting 24 hours before ascent
- Continue: for the first 2 days at target altitude
- Side effects: tingling in hands and feet (very common, harmless), increased urination, carbonated drinks taste flat
- Contraindications: sulfa drug allergy, kidney stones. Consult your doctor before use.
Practical Acclimatisation Schedule for Char Dham Pilgrims
- Day 1: Arrive Haridwar/Rishikesh (314m). Rest.
- Day 2: Travel to Barkot (1,220m) via Mussoorie if desired.
- Day 3: Yamunotri (3,291m) — ascend only for darshan, return to Barkot to sleep.
- Day 4–5: Gangotri (3,100m) — one night stay, then move.
- Day 6: Arrive Sonprayag (1,829m) — sleep at lower altitude before Kedarnath ascent.
- Day 7: Trek to Kedarnath (3,584m). This rapid ascent is where AMS is most common — stay well-hydrated and slow your pace.
For a complete Char Dham itinerary that builds in proper acclimatisation days, see our Char Dham 9N/10D package. Also review our packing list for the medicines to carry.