Everest Medical Guide: Death Zone Physiology, HACE, HAPE & Emergency Resources
At 8,848m the human body cannot acclimatise — it only deteriorates. Every hour above 8,000m adds to physiological debt that cannot be reversed on the mountain. This guide covers every medical risk from Lukla to the summit. Written by a Registered Nurse.
Medical Disclaimer. This page is written by a Registered Nurse and is intended for general informational and educational purposes only. It does not constitute professional medical advice, diagnosis, or treatment, and is not a substitute for guidance from a licensed physician or qualified expedition medicine provider. Everest climbers should undergo a thorough pre-expedition medical evaluation including cardiac screening, pulmonary function testing, and discussion of personal altitude illness history. In a life-threatening emergency, contact your expedition doctor, call Nepal emergency services at 100, or activate your rescue insurance immediately. Medical guidelines evolve; verify all protocols with your expedition medical officer and wilderness medicine provider. Global Summit Guide and its contributors assume no liability for decisions made based on the information on this page. Last reviewed: April 2026.
Everest is not a medical guide written for emergencies — it is written for the decisions made in the weeks and months before you step foot on the mountain. No other objective in this series demands this level of physiological preparation. The death zone begins at 8,000m and the summit sits 848m above that. At these altitudes the body cannot acclimatise; it can only endure, and every hour adds to a physiological debt that cannot be repaid until you descend. The medicine that matters most on Everest is the medicine practiced at sea level, six months before departure: choosing the right operator, completing the right screening, understanding your own history with altitude, and knowing the warning signs so well that recognising them becomes automatic when your judgement is most impaired.
Everest's Four Medical Risk Zones
Each zone on Everest carries a categorically different medical environment. Risks that are manageable at Everest Base Camp become life-threatening above Camp 3, and effectively unrescuable above Camp 4. Understanding the zones is the foundation of understanding Everest's medical risks.
The Death Zone: What Happens Above 8,000m
The death zone is not a metaphor. It is a physiological threshold above which the human body cannot generate enough oxygen to sustain normal cellular function, regardless of acclimatisation. Understanding what happens to your body above 8,000m is the most important medical knowledge an Everest climber can have.
Supplemental Oxygen on Everest
Supplemental oxygen does not eliminate altitude illness risk above 8,000m — it reduces it. Think of it as reducing effective altitude: breathing supplemental O₂ at 4 L/min on the summit approximates an effective altitude of roughly 6,500–7,000m. This is still severe altitude, but survivable with appropriate acclimatisation. Running out of oxygen in the death zone is a life-threatening emergency.
| Phase / Location | Typical Flow Rate | Notes |
|---|---|---|
| Sleeping at Camp 3 (7,200m) | 0.5–1 L/min | Low-flow sleeping masks preserve cylinders; prevents Cheyne-Stokes breathing disruption |
| Climbing Camp 3 to Camp 4 | 2–3 L/min | Operator standard varies; conserves supply for summit day |
| Sleeping at Camp 4 (7,920m) | 0.5–1 L/min | Essential; unprotected sleep at South Col causes extreme physiological stress |
| Summit day climbing | 3–4 L/min | Most operators; some use 4 L/min throughout for safety margin |
| Summit & descent (crux sections) | 4 L/min | Hillary Step area and Balcony; do not reduce flow at technical sections |
| HACE or HAPE treatment | 4–6 L/min | Maximum flow; combined with immediate descent; activate rescue immediately |
A regulator freeze, mask failure, or empty cylinder above 8,000m is a medical emergency. Every climber must know how to check cylinder pressure before leaving Camp 4, switch cylinders in the field (including with cold gloves), and identify regulator malfunction signs. Your Sherpa team should carry one additional cylinder as emergency reserve. If you reach the summit on your last cylinder, you have no margin for delay on the descent.
Summit fever describes the psychological state in which hypoxia, exhaustion, sunk-cost thinking, and social pressure combine to override rational risk assessment in high-altitude climbers. It is not a weakness — it is a predictable physiological response to extreme hypoxia that impairs the frontal lobe functions governing risk assessment and impulse control. The only protection is pre-commitment: agreeing on hard turn-around times and oxygen thresholds before entering the death zone, and designating your lead Sherpa as the authority to enforce them if you cannot.
Altitude Illness: AMS, HACE & HAPE on Everest
Altitude illness on Everest differs from lower peaks in one fundamental respect: above Camp 3, there is no stable altitude at which you can wait for recovery. Any significant altitude illness above 7,000m requires immediate descent. The Lake Louise Score remains the standard field assessment tool, but on Everest it is most critical during the acclimatisation rotations below Camp 3, where recognition and response options are still available. The death zone demands pre-emptive protocols, not reactive ones.
The standard Nepal route acclimatisation protocol involves multiple rotations: EBC to C2, EBC to C3, sleeping at progressively higher camps before the summit push. These are not optional schedule items — they are the physiological preparation that determines whether your body can function at all in the death zone. Climbers who compress rotations to save time or catch a weather window consistently have higher HACE and HAPE rates on summit bids. Your expedition doctor sets the rotation schedule; do not negotiate it.
Acute Mountain Sickness (AMS)
AMS is most clinically relevant during the trek to EBC and during early acclimatisation rotations. Above Camp 3, AMS by definition has already progressed to a more serious concern given the altitude involved. During the trek, the standard approach applies: stop ascending, rest, treat headache with ibuprofen. At EBC and above, take AMS more seriously than you would at lower peaks.
High Altitude Cerebral Edema (HACE)
HACE on Everest is most dangerous in the death zone, where the combination of extreme hypoxia and impaired judgement can mean that neither the patient nor those around them recognise the severity of the situation. The heel-to-toe test must be performed by companions, not self-assessed. A climber who stumbles, becomes unusually slow, or behaves out of character above Camp 3 must be assumed to have HACE until proven otherwise. Every Sherpa and climbing partner must know this protocol before summit day.
High Altitude Pulmonary Edema (HAPE)
HAPE is responsible for more Everest deaths than any other single altitude illness. It can develop without preceding AMS, it progresses rapidly at extreme altitude, and its early signs — a climber falling behind pace, a new cough, unusual breathlessness — are easily dismissed as normal fatigue on a summit push. Anyone displaying these signs above Camp 3 must be immediately assessed and, if HAPE is suspected, immediately descended with supplemental oxygen at maximum flow. Do not wait for more obvious signs.
No Everest summit is worth dying for. The mountain has a documented pattern of turning around conditions: climbers who summit return; climbers who push past their turn-around time or ignore developing HAPE symptoms frequently do not. Pre-set your turn-around time (most operators: 2:00pm absolute maximum from Camp 4), pre-set your O₂ cylinder thresholds, and give your lead Sherpa explicit authority to enforce descent regardless of your protests in a hypoxic state.
Khumbu Cough
Khumbu cough is a phenomenon specific to high-altitude environments: a severe, persistent dry cough caused by the combination of cold, dry air and increased respiratory rate at altitude. It is almost universal among Everest climbers and begins at EBC. In severe cases it causes rib fractures — a serious complication that severely limits the ability to breathe deeply and exert effort.
Khumbu Cough
Extreme Frostbite
Frostbite on Everest operates at a categorically different scale than on lower peaks. Wind chill on the summit ridge regularly reaches −50°C to −60°C (−58°F to −76°F). Tissue freezes in seconds at these temperatures. Full-thickness frostbite requiring amputation is a documented outcome for a significant proportion of serious Everest casualties — particularly of fingers, toes, nose, and ears. Mitt systems, battery-heated insoles, and layered face protection are not comfort items on this mountain. They are amputation prevention.
Extreme Frostbite
Other Significant Medical Hazards
High Altitude Retinal Haemorrhage (HARH)
Retinal haemorrhages are extremely common above 5,000m — studies show they occur in a significant majority of climbers above 6,000m. Most are asymptomatic and resolve on descent. When haemorrhages occur in the macula (the central vision area), they cause temporary or permanent vision impairment. Any sudden change in vision at altitude is a medical emergency. Report it to your expedition doctor immediately. Do not attempt to summit with new visual symptoms.
Snowblindness (Photokeratitis)
UV intensity at 8,000m is extreme — reflected from snow and ice with no atmospheric filtration. Snowblindness is a sunburn of the cornea that causes severe pain, tearing, photophobia, and temporary vision loss 6–12 hours after UV exposure. It is entirely preventable with glacier glasses (side shield, category 4 lens) worn consistently. Treatment: dark environment, lubricating eye drops, oral analgesics, cold compress. Recovery takes 24–72 hours. Always carry a backup pair of goggles — losing your only pair in the Icefall or on the summit ridge is a serious emergency.
Khumbu Icefall Hazards (Nepal Route)
The Icefall is one of the most objectively hazardous sections of any major climb in the world. Serac collapse, crevasse falls, and ladder crossings create trauma injury risk that has nothing to do with altitude. Casualties in the Icefall are typically traumatic rather than medical, but expedition doctors manage their care until helicopter extraction to EBC is possible. Crossing the Icefall before dawn — when temperature-driven serac movement is lowest — is standard expedition protocol. Minimise time in the Icefall; do not linger.
Hypothermia at Extreme Altitude
Hypothermia is a genuine risk at all camps above EBC, particularly during unexpected storms that trap climbers in tents without adequate shelter for extended periods. The standard hypothermia management protocol applies, with one critical caveat: at extreme altitude, the cardiovascular effects of severe hypothermia are compounded by the already-stressed cardiac system. Handle any patient in suspected severe hypothermia with extreme gentleness to avoid triggering ventricular fibrillation. Contact your expedition doctor for management guidance via radio before moving the patient.
Strokes (ischaemic and haemorrhagic) and cardiac events have been documented above 8,000m. Extreme altitude, dehydration, and polycythaemia (increased red blood cell mass from acclimatisation) all increase blood viscosity and thrombotic risk. Pre-existing cardiovascular conditions, including undiagnosed conditions, are a significant risk factor. Every Everest climber should undergo a cardiac evaluation including stress ECG before the expedition. Any new neurological symptoms (facial droop, arm weakness, speech difficulty) or chest pain with radiation at altitude should be treated as stroke or cardiac event — supplemental oxygen, immediate descent, and emergency contact to expedition coordinator.
International Health: Nepal & Tibet
An Everest expedition involves extended time in Kathmandu, weeks or months at EBC, and potentially significant time in Tibetan towns on the northern approach. Each environment carries distinct health risks. The altitude-related risks above EBC completely dominate the medical picture, but the weeks spent at lower elevation — especially in Kathmandu — are where food-borne illness, traveler's diarrhea, and respiratory infections most commonly strike, and a significant illness before or during acclimatisation rotations can force an entire expedition to abort.
Everest expeditions require longer lead times for vaccination than most destinations — the rabies pre-exposure series (3 doses) takes 28 days minimum, and Japanese Encephalitis vaccine (if indicated for extended rural Nepal stays) requires a 28-day series. Book your travel medicine appointment 8–12 weeks before departure. Bring your complete expedition itinerary including Kathmandu days, trek duration, and any planned safaris or side trips. Visit the CDC Nepal Travelers' Health page for current recommendations.
Vaccines for Nepal
| Vaccine | Status | Notes |
|---|---|---|
| Yellow Fever | Required if arriving from YF-risk country | Nepal requires proof of vaccination if arriving from or transiting through a country with yellow fever transmission risk within 6 days. Not required from most Western countries. Check your full itinerary including any African or South American stopovers. |
| Hepatitis A | Strongly recommended | Essential for all Nepal travel. Risk from food and water in Kathmandu, Namche, and tea houses along the trek. Two-dose series for long-term protection. Single dose provides adequate protection within 2 weeks. |
| Hepatitis B | Strongly recommended | Any medical care received in Nepal, tattooing, or dental treatment carries risk. Three-dose series; most climbers should have completed this previously. |
| Typhoid | Strongly recommended | Very common for Nepal. Risk from contaminated food and water in Kathmandu, Lukla, and Namche Bazaar. Injectable (Typhim Vi, 2 years protection) or oral (Vivotif, 5 years). Injectable preferred for simplicity. |
| Meningococcal (MenACWY) | Recommended | Recommended for all Nepal travel. Risk increases in crowded conditions (Kathmandu, trekking lodges). CDC recommends for Nepal travelers. |
| Rabies (pre-exposure) | Strongly recommended for Everest expeditions | Dog bites are very common in Kathmandu and trekking villages. Nepal has one of the world's highest rates of human rabies. Pre-exposure series (3 doses over 28 days) is strongly recommended. It does not eliminate post-exposure treatment, but buys critical time in a remote setting where post-exposure vaccines may be hours away. |
| Japanese Encephalitis | Consider for extended stays in rural lowlands | Risk in rural Terai lowland areas of Nepal, not on the Khumbu trek or at altitude. Relevant only if your itinerary includes significant time in lowland Nepal. Two-dose series over 28 days. |
| Routine vaccinations | Verify up to date | MMR, Tdap, varicella, annual influenza, COVID-19. Influenza is particularly relevant — respiratory illness at EBC can be severe and may abort an expedition. |
Regional Disease Awareness
Traveler's diarrhea is extremely common in Kathmandu and along the Khumbu trek. Giardia is particularly prevalent in Nepal's mountain water sources. A significant gut illness during acclimatisation rotations can force expedition abort — this makes food and water discipline not just a comfort issue but a mission-critical medical priority. Above EBC, most expedition operators provide treated or boiled water; confirm this with your operator.
Malaria is present in Nepal's Terai lowlands (below 1,300m) but absent along the Khumbu trekking route and at all expedition elevations. Prophylaxis is generally not needed for a standard Everest expedition that flies directly Kathmandu–Lukla. However, if your itinerary includes Chitwan, Bardia, or other lowland Nepal areas, prophylaxis is required. If you're approaching via India with time in lowland areas, discuss with your travel clinic.
Dog bites in Kathmandu and trekking villages are extremely common and Nepal has a high incidence of rabies — making the pre-exposure vaccine particularly important. Avoid all contact with stray dogs. Altitude-masked infection is a clinically important concept on Everest: the fatigue of altitude can mask the early signs of pneumonia, urinary tract infection, or other systemic infections. Monitor temperature at EBC daily — any fever should be investigated promptly by the expedition doctor. For Tibet route climbers, healthcare access in Shigatse and Lhasa is significantly more limited than in Kathmandu; carry a more comprehensive medical kit and confirm your operator has an expedition doctor on the Tibet side. Political access restrictions can also affect evacuation options — confirm this with your operator before signing any contract.
Medical Kit: EBC Through the Death Zone
Everest medical kit operates in two distinct environments: EBC and below (where the expedition doctor carries the primary kit and hospital-grade supplies), and above EBC (where each climber and Sherpa team carries a personal summit kit that must be lightweight and immediately accessible). This section covers the personal summit-day kit and the additional items specific to Everest beyond the standard altitude kit.
Most commercial Everest expeditions include a dedicated expedition doctor at EBC who carries gamow bags, IV fluids, defibrillator, comprehensive pharmacy including IV dexamethasone, amoxicillin-clavulanate, and expedition-grade oxygen systems. Know what your expedition carries and where it is. Above C2, the expedition doctor cannot reach you — your personal kit and your Sherpa team are all you have.
Above Camp 2 Personal Medications
Base Camp & Lower Mountain
Extreme Cold Injury Prevention
Snowblindness & Respiratory
Wound Management & Trauma
Hydration & Field Tools
Medical Facilities & Evacuation
The medical evacuation chain on Everest operates in stages: mountain rescue by Sherpa and climbing teams, helicopter from EBC or lower on the Nepal side, hospital treatment in Kathmandu, and international transfer for serious cases. Understanding this chain — and ensuring your rescue insurance covers every link in it — is non-negotiable before signing an expedition contract.
Above Camp 1, standard emergency services cannot reach you. Rescue is coordinated through your expedition leader and operator, who will manage Sherpa team-assisted evacuation to a helicopter-accessible altitude. Helicopter evacuation from EBC is standard in good weather; above C1 is extremely difficult and dependent on conditions. Your rescue insurance must cover helicopter evacuation, hospital treatment in Kathmandu, and international medevac. Verify this explicitly — some policies exclude high-altitude mountaineering entirely or cap at a specific altitude.
| Facility | Location | From EBC | Level / Services | Contact |
|---|---|---|---|---|
| HRA Aid Post — Everest Base Camp | EBC, Khumbu, Nepal (seasonal) | On-site | Expedition medicine staff · O₂ · Gamow bag · Helicopter coordination · Open spring expedition season | Via expedition leader or +977 1 4440292 |
| CIWEC Clinic Travel Medicine Center | Lazimpat, Kathmandu, Nepal | ~130 km by air | Premier expedition medicine clinic · Altitude illness specialists · Pre-expedition screenings · Post-expedition care | +977 1 4424111 |
| Patan Hospital | Lagankhel, Lalitpur, Kathmandu | ~130 km by air | Full hospital · Surgical · ICU · Standard evacuation receiving hospital for Everest casualties | +977 1 5522266 |
| HAMS Hospital | Dhumbarahi, Kathmandu | ~130 km by air | Modern private hospital · Good ICU capability · Preferred by many expedition operators for serious cases | +977 1 4361606 |
| Bumrungrad International Hospital | Bangkok, Thailand | International transfer | Level III equivalent · Full specialist services · Hyperbaric chamber · Standard international evacuation destination for complex Everest cases | +66 2 667 1000 |
| Fishtail Air / Dynasty Air | Kathmandu (helicopter operators) | Helicopter to EBC | Primary helicopter evacuation providers for Khumbu · Confirm your rescue insurance uses these operators | Coordinated via expedition operator |
Standard travel insurance does not cover high-altitude mountaineering. You need a specialist policy from providers such as Global Rescue, Ripcord, Garuda Rescue, or GEOS (included with Garmin inReach). Verify explicitly: (1) altitude ceiling covered — must be above 8,848m; (2) helicopter evacuation from Nepal; (3) international medical transfer; (4) mountain rescue coordination services. Many expedition operators include rescue insurance in their package — confirm this with your operator and obtain the policy number before departure.
The Summit Is Optional. Getting Down Is Not.
Everest kills people every year who were competent, fit, and experienced — not because the mountain is unpredictable, but because the death zone impairs the very judgement needed to make survival decisions. Every protection you have on this mountain must be put in place before you enter the death zone: the turn-around times, the O₂ thresholds, the Sherpa authority to enforce descent. The medical guide you've read on this page matters most not on summit day, but in the months of preparation before you leave home.