Why Altitude Sickness Is More Dangerous — and More Common —Than You Think

When Ryan Wach stood atop Mount Whitney with his 14-year-old son, he didn’t suspect anything could go wrong. The father-and-son duo had ascended a non-technical hiking trail, free from snow and ice under the July sun. With Zane an experienced distance runner and triathlete, Ryan had full confidence in his son’s ability to handle the iconic 14,505-foot summit. What he didn’t take into account was that, at altitude, sickness can creep up on anyone. That’s when he saw his hallucinating son walk off the edge of the trail and fall 120 feet onto solid granite.

What is altitude sickness? 

Altitude sickness, also known as mountain sickness, is caused by low oxygen levels associated with elevation. It typically occurs above 8,000 feet, but some people may be affected even below that level. The first symptom is often a headache, followed by a range of gastrointestinal, neurological, respiratory, and cardiovascular issues. Ignoring these warning signs can lead to serious conditions such as cerebral or pulmonary edema. Beyond the medical risks, people affected may also experience poor decision-making, confusion, and even hallucinations.

Why altitude sickness doesn’t care about your climbing resume 

The striking thing about altitude sickness is that it can affect anyone. Up to 75 percent of people traveling above 10,000 feet experience it, and even seasoned mountaineers are not immune. In 2006, British climber David Sharp tragically succumbed to it during a solo attempt on Everest. But you don’t need to enter the Himalayan “death zone” to be at risk. Just a couple of weeks after Zane Wach’s fall on Mount Whitney, a 50-year-old hiker died on nearby Mount Shasta after a similar fall likely caused by altitude sickness.

Research might soon beat mountain sickness 

The effects of low oxygen on the body are a major concern not only for mountaineers, but also for researchers and military personnel operating at altitude. As a result, significant resources are being invested in studying not only how to treat but also how to prevent mountain sickness. One recent and surprising finding suggests that probiotics may be associated with improved oxygen availability in the blood. Although scientists are not yet certain of the exact mechanism linking the gut microbiome to oxygen regulation, this could soon become part of preventative protocols for people working or recreating at altitude.

A more radical approach involves inhaling xenon, a gas that allows the body to acclimate more quickly. In 2025, a group of British climbers took less than a week to scale Mount Everest thanks to the controversial use of the gas, considered by many as cheating. Xenon could however become the standard for rescue and military missions, although its long-term effects are still unknown.

Acclimatization still key for altitude sickness prevention

The traditional way to tackle altitude sickness has not changed since humans first began venturing into high elevations: gradual acclimatization. 

If you go above 10,000 feet, increase your sleeping altitude by no more than 1,000 feet per day. Take a rest day for every 3,000 feet gained. You can climb more than 1,000 feet in a day as long as you descend to sleep at a lower altitude. If you begin to show symptoms of moderate altitude illness, do not ascend further until they subside. A high-carbohydrate diet and proper hydration are also important.

With single-day trips, like Sierra Nevada’s popular scenic hikes, it might seem tempting to skip acclimatization, but even for extremely fit individuals, the effects of low oxygen on the body and mind can appear suddenly. It is crucial to ascend slowly as fatigue increases the risks. Whenever possible, planning prolonged trips allowing for rest days and sleeping at lower elevations than those reached during the day is the best way to reduce danger.

According to rescuers, it was a miracle that Zane Wach survived his 120-foot fall. After recovering from his injuries, which necessitated a medically induced coma, he was able to return to full activity and to the mountains.