Altitude illness symptoms and warning signs

Acute mountain sickness develops after the body is exposed to lower oxygen levels at elevation, commonly within hours of an ascent. A new headache is often accompanied by loss of appetite, nausea, light-headedness, unusual fatigue, or disturbed sleep. Symptoms may resemble dehydration, exhaustion, a viral illness, alcohol effects, or motion sickness, so the timing after a climb and the combination of complaints matter.

More severe altitude illness can affect the brain or lungs. Brain involvement may cause confusion, unusual behaviour, marked drowsiness, or poor coordination. Lung involvement may cause breathlessness at rest, a persistent cough, reduced exercise ability beyond ordinary exertion, chest tightness, or blue-grey lips.

Stop ascending and tell a companion as soon as symptoms appear. Rest at the current elevation, keep warm, drink according to thirst, and avoid alcohol, sedatives, and strenuous exertion. Simple pain relief or anti-nausea treatment may make you more comfortable, but symptom relief is not permission to climb higher.

If the person is not improving or becomes worse, descend to a lower elevation. Travel with someone who can monitor walking, alertness, and breathing. A pre-travel clinician can help travellers with previous altitude illness create an ascent and medication plan.

Treat confusion, stumbling or inability to walk heel-to-toe, severe drowsiness, collapse, breathlessness while resting, coughing frothy fluid, or blue-grey colour around the lips as an emergency. Arrange assisted descent and emergency medical care immediately. Use oxygen if trained help and equipment are available, but do not delay descent while waiting for improvement.

Discuss your highest sleeping elevation, daily gains, rest days, previous reactions at altitude, heart or lung conditions, and access to evacuation. Ask how to distinguish expected exertional breathlessness from a warning sign, whether preventive medication suits you, and what your travel group should do if symptoms develop overnight.