Preventing acute mountain sickness

Build rest and acclimatisation into the itinerary, avoid a rapid jump to a much higher sleeping altitude, and keep early exertion gentle. A travel-health clinician can assess whether preventive acetazolamide is suitable based on the planned route, previous altitude illness, health conditions, and current medicines.

At altitude, lower air pressure means less oxygen reaches the body with each breath. Acclimatisation allows breathing, circulation, and other body responses to adjust over time. Fitness does not remove susceptibility, and a person who previously travelled high without symptoms can still become unwell on another trip.

Acute mountain sickness commonly presents with headache after gaining altitude, together with nausea, dizziness, fatigue, or disturbed sleep. Symptoms after ascent should be treated as a warning to stop going higher; continuing upward can allow a mild illness to progress.

Choose an itinerary that gains sleeping altitude slowly and includes easier days. Stay well hydrated according to thirst, eat enough, and avoid heavy alcohol use or unaccustomed sedating medicines that can cloud symptom recognition or breathing. Do not rely on excessive water intake, physical fitness, or a brief daytime acclimatisation stop as protection.

Agree on a daily symptom check with companions and make descent plans before setting out. If headache or other compatible symptoms develop after ascent, remain at the same altitude, rest, and monitor closely. Descend if symptoms worsen or fail to settle; never leave an unwell traveller alone.

Begin descent and seek urgent medical help for confusion, unusual behaviour, severe drowsiness, inability to walk heel-to-toe, breathlessness at rest, chest tightness, blue or grey lips, or a cough accompanied by marked breathing difficulty. These features may indicate dangerous swelling affecting the brain or fluid in the lungs.

Do not wait for morning or for medicines to work when severe signs are present. Give supplemental oxygen if available and trained to do so, keep the person warm, minimise exertion, and descend with assistance while arranging emergency support.

Share the highest sleeping altitude, rate of ascent, remote sections, and prior altitude symptoms. Ask whether your heart or lung condition changes the plan, whether acetazolamide is appropriate, when it should be started, what side effects to expect, and how to distinguish early altitude illness from another cause of headache or nausea.