People die on Mount Everest primarily from falls, exhaustion, and altitude sickness, though these causes overlap more than most people realize. The mountain has killed roughly 300 climbers since the first summit attempts began over a century ago, with 18 deaths in 2023 alone. What makes Everest so lethal isn’t any single hazard. It’s the combination of extreme altitude, brutal weather, treacherous terrain, and the near-impossibility of rescue once something goes wrong above 8,000 meters.
The Death Zone and What It Does to Your Body
Above 26,000 feet (7,925 meters), climbers enter what’s known as the “death zone,” where the oxygen level is not sufficient to sustain human life for long. At the summit of Everest (29,029 feet), the air pressure is roughly a third of what it is at sea level. Blood oxygen saturation, which normally sits around 95 to 100 percent, can drop into the 60s or lower. At those levels, the body starts shutting down: muscles lose power, the brain gets less blood flow, and the body hemorrhages heat through rapid breathing.
This is the core problem of Everest. Every hour spent in the death zone is borrowed time. Climbers use supplemental oxygen, typically flowing at about 4 liters per minute during the ascent, which meaningfully improves survival. The difference is stark: 1 in 12 climbers descending from the summit without supplemental oxygen dies, compared to 1 in 34 among those using it. If a regulator freezes, a tank runs empty, or a mask fails at extreme altitude, the consequences can be fatal within hours.
How Altitude Sickness Kills
The two lethal forms of altitude sickness are high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). In HAPE, fluid leaks into the lungs, making it progressively harder to breathe. In HACE, low oxygen triggers blood vessels in the brain to dilate and leak, causing the brain to swell. HACE symptoms typically appear within one to two days after ascending and include confusion, loss of coordination, delirium, and altered consciousness. Both conditions can kill quickly if a climber doesn’t descend.
The real danger is that altitude sickness is underreported as a cause of death. When a climber dies from a fall or exhaustion above 8,000 meters, altitude-related brain swelling may well have caused the confusion or poor coordination that led to the fall in the first place. One expedition physician noted that within a group of just 15 climbers, two developed HAPE and one developed HACE, a rate far higher than the 1 to 3 percent incidence predicted by medical literature. The official cause of death on Everest is usually reported by a fellow climber, not a medical examiner, so the role of altitude illness in many deaths is likely underestimated.
Impaired Judgment at Extreme Altitude
Low oxygen doesn’t just weaken the body. It degrades thinking. As altitude increases, climbers experience measurable declines in short-term memory, judgment, attention span, and decision-making ability. At extreme elevations, this can progress to full confusion and behavioral abnormalities.
This cognitive impairment feeds what climbers call “summit fever,” the dangerous compulsion to keep pushing upward even when conditions or physical symptoms demand turning back. A climber whose brain is starved of oxygen may not recognize how exhausted they are, may misjudge the time needed to descend, or may ignore deteriorating weather. These aren’t character flaws. They’re predictable consequences of hypoxia. Many fatal decisions on Everest, continuing past a turnaround time, not turning back at the first signs of illness, were made by people whose brains were no longer functioning normally.
The Khumbu Icefall
On the Nepal side of Everest, every climber must pass through the Khumbu Icefall, a mile-long stretch of fractured glacier between about 18,000 and 19,000 feet. House-sized blocks of ice shift and collapse without warning. Climbers cross deep crevasses on aluminum ladders lashed together, and hanging glaciers above can release avalanches at any time. One veteran mountaineer has called it “essentially a game of Russian roulette.” Expeditions typically move through the icefall between 2 and 5 a.m. by headlamp, when cold temperatures keep the ice more stable. During the day, warming sun causes the ice to crumble and avalanches to release.
In 2014, an avalanche in the icefall killed 16 Sherpas in a single event, making it the deadliest day on Everest at that time. The following year, an earthquake triggered an avalanche that killed at least 17 people at Base Camp. These mass-casualty events are reminders that even below the death zone, Everest presents hazards that no amount of skill can fully mitigate.
Crowding and Traffic Jams
Everest has become increasingly crowded, and that crowding kills people. On summit day, climbers converge on narrow sections of the route, particularly near the top, creating bottlenecks where dozens of people may be waiting in a single-file line. During a stretch of good weather in 2019, seven climbers died in a single week, with long lines contributing to multiple deaths. One 27-year-old climber was stuck in traffic for more than 12 hours and died of exhaustion.
The danger of these delays is straightforward. Every extra hour spent above 26,000 feet drains supplemental oxygen supplies, increases the risk of altitude sickness, and deepens exhaustion. Climbers who planned a 10-hour summit day may find themselves out for 16 or more. And if someone falls ill in a traffic jam, descending quickly to a lower, safer altitude is physically impossible when the route is blocked with other climbers.
Why Sherpas Face Greater Risk
About one-third of all Everest deaths have been Sherpas. While they are present on the mountain in greater numbers than any single nationality of foreign climbers, they also face far more exposure to the mountain’s worst hazards. A paying client might pass through the Khumbu Icefall a handful of times during an expedition. A working Sherpa, hauling tents, food, ropes, and oxygen bottles, might make 15 to 20 trips through the same gauntlet.
Sherpas also face pressure from clients that can override their own judgment. In one case, a 19-year-old Sherpa working his second season on Everest requested that his client abandon their summit attempt when weather turned bad. The client refused. Both men ended up unconscious in the snow during the descent. The dynamic between a hired guide and a client who has paid tens of thousands of dollars for a summit attempt creates situations where Sherpas absorb risk that foreign climbers generate.
Why Rescue Is Nearly Impossible
On most mountains, a climber who gets into trouble can be evacuated by helicopter or carried down by a rescue team. On Everest, neither option reliably exists above a certain altitude. The official maximum altitude for helicopter operations is around 7,000 meters (about 23,000 feet). In exceptional cases, helicopters have reached 8,000 meters, but only with an empty cabin and minimal crew. These flights are not officially approved and depend on perfect weather conditions.
Above 8,000 meters, rescue depends entirely on other climbers, who are themselves hypoxic, exhausted, and carrying limited oxygen. Dragging an incapacitated person down steep, icy terrain in the death zone is extraordinarily dangerous and often physically impossible. Many climbers who collapse above 8,000 meters simply cannot be saved, and their bodies remain on the mountain. This is the brutal arithmetic of Everest: the place where people are most likely to need help is the place where help is least available.