Altitude sickness

Altitude sickness, also called acute mountain sickness, is an illness triggered by the lower air pressure and oxygen levels at high altitude, which affect the brain, lungs and other organs. It can affect climbers, hikers, skiers and other travellers, usually at heights above roughly 2,400 metres. Rapid ascent is the main risk factor, along with living near sea level, a previous episode, poor acclimatisation, alcohol use, and heart, nervous system or lung problems. Symptoms are usually mild and include headache, nausea, dizziness, tiredness, poor appetite and disturbed sleep, but confusion, breathlessness at rest and fluid on the lungs or brain are life-threatening. Clinicians examine the person and listen to the chest, sometimes adding blood tests, a chest x-ray, an electrocardiogram or a brain scan. Treatment centres on rest and descent to a lower altitude, with extra oxygen, acetazolamide or dexamethasone in more serious cases.

Seek emergency care for a first seizure, a seizure lasting more than five minutes, a sudden severe headache, new weakness or confusion, or thoughts of harming yourself. See a doctor for headaches that are more frequent or changing, memory problems that affect daily life, or low mood lasting more than two weeks. Call the local emergency number for any symptom that is sudden and severe. This page is a reference for healthcare professionals and does not replace an assessment.