Acute Mountain Sickness
Acute mountain sickness is headache with symptoms such as nausea, dizziness, fatigue or poor sleep after ascending to high altitude too quickly.
Key takeaways
- Stop ascending when symptoms begin; further ascent can allow a mild illness to progress.
- Gradual acclimatisation is the main prevention, while preventive medicine is reserved for selected itineraries or risk profiles.
- Confusion, inability to walk straight or breathlessness at rest suggest life-threatening altitude illness, not simple AMS.
The listings below do not replace an ascent plan or medical assessment; suitability depends on altitude, itinerary and health history.
Responding to symptoms
Rest at the same altitude and monitor closely. Mild symptoms often improve with acclimatisation, fluids as needed and simple symptom relief. Descent is the definitive response when symptoms worsen or fail to improve; oxygen may be needed in severe illness.
Prevention and medicine
Sleeping altitude should increase gradually where possible. Acetazolamide can speed acclimatisation for some travellers but is not a substitute for a sensible ascent rate. Existing heart or lung disease, pregnancy and prior severe altitude illness warrant personalised advice before travel.
When to seek urgent care
Descend and obtain emergency help for confusion, severe drowsiness, inability to walk straight, breathlessness at rest, chest tightness, blue lips or a wet cough at altitude.