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

This guideline focuses on sleeping altitude, not daytime elevation. Sleeping above 2,450 meters already poses a risk of altitude sickness. Once above 3,000 meters, you should only raise your nighttime altitude by 500 meters per night, allowing an additional day of acclimatization for every 1,000-meter increase. Symptoms such as headache, nausea, unsteady gait, altered mental state, or shortness of breath even at rest indicate the need to descend. Descending takes priority over oxygen therapy or medication.

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 above 2,450 meters increases the risk of altitude sickness. Without prompt descent, high-altitude cerebral edema and pulmonary edema — fluid buildup in the brain and lungs — can be fatal.

The rule specifically refers to sleeping altitude, not daytime elevation. Headache, nausea, unsteadiness, confusion, or breathlessness at rest are clear signs to descend. Descending should always come before oxygen use or medication; continuing upward while on oxygen is unsafe.

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