What is Altitude Sickness?
Acute Mountain Sickness (AMS) is caused by ascending too quickly to high altitude, where reduced atmospheric pressure means less oxygen reaches the blood with each breath. It can affect anyone — fitness level, age, and prior altitude experience are not reliable predictors. Even elite athletes get AMS.
The Three Forms — From Mild to Life-Threatening
1. AMS (Acute Mountain Sickness) — Common, Manageable
Symptoms: Headache, nausea, fatigue, loss of appetite, dizziness, poor sleep. Usually begins 6–12 hours after arrival at altitude. Affects up to 40% of trekkers at 3,500 m.
Action: Do not ascend further. Rest at current altitude. Drink water. Take ibuprofen for headache. Re-evaluate in 24 hours. If symptoms don’t improve — descend.
2. HACE (High Altitude Cerebral Edema) — Serious, Requires Immediate Action
Symptoms: Severe headache unresponsive to medication, loss of coordination (ataxia — test by walking heel-to-toe), altered mental state, confusion.
Action: Descend immediately, minimum 500 m. This is a medical emergency.** Administer dexamethasone 8 mg if available. A Gamow bag (portable hyperbaric chamber) can be life-saving while awaiting evacuation.
3. HAPE (High Altitude Pulmonary Edema) — Potentially Fatal
Symptoms: Dry cough (progressing to producing pink frothy sputum), severe breathlessness at rest, crackling sounds when breathing, blue lips or fingertips.
Action: Descend immediately — this is the most common cause of altitude-related death. Administer nifedipine 30 mg (slow release) if available. Use supplemental oxygen if available. Do not wait for morning.
The Golden Rules of Acclimatisation
- “Climb high, sleep low” — ascend during the day, return to a lower camp to sleep
- Above 3,000 m, ascend no more than 300–500 m per day (sleeping altitude)
- Take a rest day every 1,000 m of altitude gain
- Stay hydrated — aim for 3–4 litres of water per day
- Never ascend with AMS symptoms — “walking it off” does not work at altitude
Diamox (Acetazolamide) — Does It Work?
Yes, acetazolamide (Diamox) is proven to accelerate acclimatisation and reduce the incidence of AMS. Typical dose: 125 mg twice daily, starting 24 hours before ascent. Side effects include increased urination, tingling in fingers, and it makes carbonated drinks taste flat. It is a sulfa drug — do not take if you have a sulfa allergy. Discuss with your doctor before travel. Available in Kathmandu pharmacies without prescription.
Monitoring with a Pulse Oximeter
A pulse oximeter clips to your finger and measures blood oxygen saturation (SpO2). At sea level, SpO2 should be 95–100%. At Namche (3,440 m) expect 88–92%. At EBC (5,364 m), 80–85% is normal. If your SpO2 drops suddenly or you feel unwell, descend and reassess. Our guides carry oximeters on all treks.
Emergency Evacuation from Nepal’s Mountains
Helicopter rescue is available from virtually anywhere in Nepal with an emergency call. Rescue from EBC or Annapurna is typically 20–40 minutes by helicopter. Costs run USD 3,000–6,000 — comprehensive travel insurance with helicopter evacuation cover is non-negotiable. We assist all our guests with emergency rescue coordination 24/7.
