Gradually increase your sleeping altitude when heading to high elevations; if symptoms worsen, descend immediately — don’t tough it out

It requires an extra day or two for acclimatization. Preventive medications are prescription-only, so you must consult a doctor before traveling. The main challenge is fitting these days into an otherwise tight itinerary.

Sleeping at or above 2,450 meters carries a risk of altitude sickness. High-altitude cerebral edema and pulmonary edema (fluid accumulation in the brain and lungs) can be fatal if you do not descend to a lower altitude in a timely manner. The US CDC Yellow Book provides three rules for preventing severe illness: recognize early symptoms and be willing to admit them; when symptoms are present, no matter how mild, do not sleep at a higher altitude; if symptoms continue to worsen after resting at the same altitude or receiving treatment, descend. Acute mountain sickness usually improves quickly after descending at least 300 meters. In remote areas, high-altitude cerebral edema requires immediate descent, and should be treated with both dexamethasone and oxygen if available. In most cases, high-altitude pulmonary edema requires immediate descent, as descending and oxygen administration are far more effective than taking medication.

美国疾病控制与预防中心. 黄皮书·高海拔旅行与高原病：「Any unacclimatized traveler proceeding to a sleeping altitude of ≥2,450 m (≥8,000 ft)—and sometimes lower—is at risk for altitude illness」；上升速度「500 m (1,650 ft) per night in sleeping altitude once above 3,000 m (9,800 ft)」，每上升 1000 米加一天适应日；乙酰唑胺预防「125 mg twice a day; 250 mg twice a day if >100 kg body weight」；「If symptoms become worse despite rest or treatment at the same elevation」必须下撤；「Never ascend to sleep at a higher altitude when experiencing symptoms of altitude illness, no matter how minor the symptoms seem」「AMS improves rapidly with a descent of 300 m (1,000 ft) or more」「In remote areas, initiate descent for anyone suspected of having HACE」「Descent and oxygen are much more effective treatments than medication」. https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/high-altitude-travel-and-altitude-illness.html；荒野医学会 (2024). 急性高原病预防、诊断与治疗临床实践指南（2024 更新）. Wilderness & Environmental Medicine. https://doi.org/10.1016/j.wem.2023.05.013

The calculation is based on 'how high you sleep,' not how high you go during the day. If symptoms appear, do not sleep at a higher altitude; if they worsen after rest, descend. Unsteady walking, changes in consciousness, or being unable to breathe even while still may indicate cerebral or pulmonary edema, which requires immediate descent in the wild. Descending and oxygen administration are more important than taking medication.