Altitude sickness levels: symptoms and action

Mild illness often brings headache with nausea, dizziness, unusual tiredness, poor appetite, or disturbed sleep after gaining height. Worsening symptoms, trouble walking straight, confusion, breathlessness at rest, or a wet cough indicate a more serious problem. Do not continue upward while symptoms are present.

Acute mountain sickness is the milder syndrome. It reflects difficulty adjusting to lower oxygen pressure and is judged by symptoms rather than a single device reading. High-altitude cerebral oedema affects the brain, causing loss of coordination, marked drowsiness, confusion, or altered behaviour. High-altitude pulmonary oedema affects the lungs, producing breathlessness out of proportion to effort, reduced exercise ability, chest tightness, cough, or noisy breathing.

A mild headache can have other causes, including dehydration or caffeine withdrawal. At altitude, however, a new headache combined with other typical symptoms deserves a cautious response.

For mild symptoms, stop gaining sleeping altitude, rest, keep warm, drink normally, and avoid heavy exertion or alcohol. A simple pain reliever may ease headache if it is normally safe for you, but feeling better after medicine is not permission to climb higher.

If symptoms fail to settle or become stronger at the same height, descend with another person. Serious brain or lung signs call for immediate descent, supplemental oxygen when available, minimal exertion, and emergency assistance. Oxygen and medicines can support evacuation, but they do not make a continued ascent safe.

Arrange emergency help for confusion, inability to walk heel-to-toe, collapse, severe drowsiness, breathlessness while resting, blue or grey lips, coughing frothy fluid, or rapidly worsening weakness. Begin descent if it can be done safely; do not leave the person alone or make them walk if exertion worsens breathing.

Seek medical assessment for persistent symptoms after descent, or whenever another illness could explain the symptoms. Fever, one-sided weakness, chest pain, fainting, or a severe sudden headache need evaluation rather than being assumed to be altitude sickness.

Discuss whether your route allows gradual acclimatisation, how a previous altitude reaction changes your plan, and which rescue options exist along the route. Ask whether heart or lung disease, pregnancy, sleep apnoea, regular medicines, or a history of severe altitude illness calls for a tailored itinerary or preventive prescription.