Travel Guide

HACE and HAPE on Nepal Treks: The Two Killers and When to Descend

Q: At what altitude do HACE and HAPE usually occur?

Both illnesses typically strike above 3,000 meters, with most serious cases occurring between 3,500 and 5,000 meters on Nepal treks like Everest Base Camp, Manaslu, and the Annapurna Circuit's Thorong La Pass.

Q: Does travel insurance cover helicopter rescue in Nepal?

Standard travel insurance is not enough. You need a policy that specifically covers high-altitude helicopter evacuation up to 6,000 meters and AMS/HAPE/HACE medical treatment. This is legally required for Restricted Area Permits.

Q: Does Diamox prevent HACE and HAPE?

Diamox (acetazolamide) helps prevent and reduce AMS, which lowers the chance of progression to HACE. It does not directly prevent HAPE. The only reliable cure for both is immediate descent.

Sandeep Shrestha

June 23, 202611 min read

What Are HACE and HAPE?
HACE: When the Brain Swells
HAPE: When the Lungs Fill With Fluid
The One Rule That Saves Lives: Descend
Prevention: Climb Slow, Sleep Low
HACE vs HAPE: Quick Comparison
Helicopter Evacuation and Insurance You Actually Need
Eating and Drinking to Stay Safe High Up
The 2026 Guide Requirement Is a Safety Feature
Where These Illnesses Strike Most on Popular Routes
Frequently Asked Questions

The most dangerous moment on a Nepal trek is rarely a slip on the trail or a swinging suspension bridge. It is the quiet decision to push higher when your body is screaming to stop. Two illnesses, HACE and HAPE, are the reason experienced guides watch their trekkers like hawks above 3,000 meters. Both can turn a healthy person into a medical emergency within hours.

We coordinate treks across the Everest, Annapurna, and Manaslu regions, and we have seen how fast a manageable headache can spiral. This guide explains exactly what these two killers are, how to recognise them, and the one action that saves lives every single time: going down.

What Are HACE and HAPE?

An exhausted hiker sitting on a rocky trail with trekking poles, holding their head in pain due to altitude sickness symptoms. — Listen to your body: Recognizing and managing the early warning signs of altitude sickness on high mountain passes.

HACE (High Altitude Cerebral Edema) is fluid swelling in the brain, marked by confusion, stumbling, and loss of coordination. HAPE (High Altitude Pulmonary Edema) is fluid leaking into the lungs, marked by breathlessness at rest and a wet, gurgling cough. Both strike above 3,000 meters and are fatal without immediate descent.

Think of them as the severe ends of altitude illness. Most trekkers first feel Acute Mountain Sickness (AMS): headache, nausea, poor sleep, and fatigue. AMS is common and usually mild. The danger is when it is ignored and progresses into HACE or HAPE, which are genuine emergencies.

You can read our broader overview of altitude sickness in Nepal to understand the full spectrum before your trip.

HACE: When the Brain Swells

HACE is the brain version of altitude illness. Fluid builds up inside the skull, causing the brain to swell. The hallmark sign is ataxia, a loss of balance and coordination, often combined with confusion and severe drowsiness. Once HACE sets in, a trekker can lose the ability to walk within hours and must descend immediately.

The classic field test our guides use is asking the trekker to walk a straight line, heel to toe, as if on a tightrope. If they cannot do it, treat it as HACE until proven otherwise.

Warning Signs of HACE

Loss of coordination (cannot walk straight)
Confusion, irrational behaviour, or strange decisions
Severe, drug-resistant headache
Extreme drowsiness and difficulty waking
Hallucinations in advanced cases

A trekker with HACE often does not realise how impaired they are. This is why we travel with companions and licensed guides. The person beside you may notice the slurred speech or wobbly steps before you ever feel something is wrong.

HAPE: When the Lungs Fill With Fluid

HAPE is fluid accumulation in the lungs that blocks oxygen transfer into the blood. The earliest warning is breathlessness at rest and a dramatic drop in exercise tolerance, often with a dry cough that turns wet. HAPE can kill faster than HACE and frequently appears on the second or third night at a new high altitude.

A trekker who could climb steadily yesterday but now gasps for air after ten steps is showing a red flag. Listen for crackling or bubbling sounds when they breathe.

Warning Signs of HAPE

Breathlessness while resting, not just while walking
A cough producing frothy or pink-tinged sputum in advanced cases
Tightness or congestion in the chest
Unusual fatigue and weakness
Blue tinge to lips or fingernails (cyanosis)
Rapid heart rate even at rest

HAPE often appears without a bad headache, which is why some trekkers dismiss it. Do not. Any breathlessness at rest above 3,000 meters demands immediate descent and medical attention.

The One Rule That Saves Lives: Descend

White and blue box packaging of Acetazolamide 250 mg tablets containing 112 tablets — Generic Acetazolamide 250 mg tablets, commonly prescribed for altitude sickness prevention, glaucoma, and fluid retention.

For both HACE and HAPE, the definitive treatment is immediate descent of at least 500 to 1,000 meters, ideally to an altitude where the trekker last felt well. Bottled oxygen, medication, and a portable Gamow bag buy time, but they are not substitutes for getting down. Never let a sick trekker spend another night high.

If symptoms appear at night, do not wait until morning. Descending in darkness with headlamps and a guide is far safer than gambling on dawn. Many fatalities happen because a group decided to "see how they feel in the morning."

Drugs are supportive only. Dexamethasone is used for HACE, and Nifedipine for HAPE, alongside acetazolamide. Our guide to Diamox and acetazolamide for trekking explains how these fit into a safe plan, but always travel with a guide who knows their use.

Prevention: Climb Slow, Sleep Low

A hiker in a bright red sweater and blue backpack covering his face in pain due to headache and altitude sickness symptoms on a dry mountain trail.

The single most effective prevention is a slow, graded ascent. Above 3,000 meters, your sleeping elevation should not rise by more than 300 to 500 meters per day, with a mandatory acclimatization rest day every 1,000 meters of gain. Hydration, avoiding alcohol, and eating well all matter, but pacing is king.

On the Everest Base Camp route, this means a full rest day at Namche Bazaar (3,440 meters) and another at Dingboche (4,410 meters). On the Annapurna Circuit, you take rest days at Manang (3,540 meters) before tackling the Thorong La Pass (5,416 meters). Skipping these to save time is the most common mistake we see.

Acclimatization Day-By-Day Targets

Ready? Let's go.

The ultimate guide to planning your dream web travel adventure with the experts from myeasyguide.

Spam free. Unsubscribe anytime. We respect your privacy.

Helicopter Evacuation and Insurance You Actually Need

Private helicopter landing next to the massive snow-covered peak of Mount Everest in Nepal. — Source: Sherine / Pexels, Helicopter transfering supplies in the world's most iconic mountain destination.

Standard travel insurance does not cover high-altitude rescue. You must hold a policy that explicitly covers emergency helicopter evacuation up to 6,000 meters and medical treatment for AMS, HAPE, and HACE. This specific coverage is legally required to obtain Restricted Area Permits for regions like Manaslu and Upper Mustang.

On the trail past Namche Bazaar or Jomsom, there are no ATMs and no hospitals with intensive care. A helicopter is often the only way out, and operators may require proof of insurance or a deposit before flying. Carry your policy number and the insurer's emergency phone line saved offline.

Nepal Telecom (NTC) is the most reliable network in the Everest and Manaslu regions for emergency calls, while Ncell covers the Annapurna area well. Buy a local SIM in Kathmandu before you head out.

Eating and Drinking to Stay Safe High Up

At altitude your body needs clean carbohydrates and steady hydration far more than heavy protein. We strongly recommend the traditional Dal Bhat: lentil soup, rice, and vegetable curry, which comes with free refills and gives sustained energy for long climbing days.

Stick to vegetarian meals on the trail. In the Buddhist Khumbu region, slaughtering animals is prohibited by local law, so all meat is carried up on foot over several days without refrigeration. The food poisoning risk simply is not worth it at altitude, where your body is already under stress. Explore more in our guide to teahouse food in Nepal.

For water, never buy plastic bottled water on the trail. Carry a reusable bottle and an active purification system such as a UV purifier, a Sawyer squeeze filter, or chlorine dioxide drops. Dehydration worsens altitude illness, so aim for three to four litres a day.

The 2026 Guide Requirement Is a Safety Feature

As of 2026, Nepal strongly enforces the use of licensed guides across most major trekking regions, and in Restricted Areas like Manaslu, Upper Mustang, Dolpo, and Tsum Valley it is mandatory. A single trekker can now obtain a Restricted Area Permit (the old two-person minimum is gone), but they must still hire a licensed guide, with the ratio capped at one guide per seven trekkers.

From a medical standpoint, this rule is a gift. A trained guide spots ataxia, monitors your breathing, carries a pulse oximeter, and makes the descent call when your own judgement is clouded by HACE. Review the current framework in our overview of Nepal trekking rules and costs.

Where These Illnesses Strike Most on Popular Routes

The high passes and base camps are the danger zones. On the Everest Base Camp trek, the risk builds from Dingboche upward. The Thorong La Pass at 5,416 meters and Tilicho Lake on the Annapurna Circuit are notorious for catching people who climbed too fast.

The Cho La Pass, the Three Passes circuit, and Gokyo Lakes all involve sustained time above 4,500 meters. These are not routes to rush, and they are not for trekkers who skipped acclimatization days lower down.

Frequently Asked Questions

What is the difference between HACE and HAPE?

HACE is fluid swelling in the brain, causing confusion and loss of coordination. HAPE is fluid in the lungs, causing breathlessness at rest and a wet cough. Both are fatal without immediate descent and can occur together.

At what altitude do HACE and HAPE usually occur?

Both typically strike above 3,000 meters, with most serious cases between 3,500 and 5,000 meters on treks like Everest Base Camp, Manaslu, and the Thorong La Pass crossing.

Can you die from altitude sickness in Nepal?

Yes. Untreated HACE or HAPE can kill within hours. Mild AMS is rarely fatal, but ignoring it and climbing higher allows progression to these deadly stages.

Does Diamox prevent HACE and HAPE?

Diamox (acetazolamide) helps prevent AMS by speeding acclimatization, and since HACE often develops from unmanaged AMS, reducing AMS indirectly lowers HACE risk. It is not an established preventive for HAPE. The only reliable treatment for either condition is immediate descent.

How fast can HAPE develop?

HAPE often appears on the second or third night at a new high altitude and can become life-threatening within hours. Breathlessness at rest is the critical early warning.

Does travel insurance cover helicopter rescue in Nepal?

Standard policies do not. You need coverage that explicitly includes helicopter evacuation up to 6,000 meters and AMS/HAPE/HACE treatment. This is legally required for Restricted Area Permits.

Should I descend at night if symptoms appear?

Yes. Never wait until morning if a trekker shows signs of HACE or HAPE. Descending in darkness with a guide is far safer than spending another night high.

How much should I descend to recover?

Descend at least 500 to 1,000 meters, ideally to the altitude where the person last felt completely well, and seek medical attention.

Can fit, young athletes get HACE or HAPE?

Absolutely. Fitness offers no protection. In fact, strong, fast climbers sometimes ascend too quickly and are at higher risk. Susceptibility is individual and unpredictable.

Is a pulse oximeter useful on the trail?

Yes. Many licensed guides carry one to monitor blood oxygen saturation. A consistently low or falling reading combined with symptoms is a strong reason to descend.

Can I get oxygen on Nepal treks?

Some higher teahouses and rescue posts stock bottled oxygen and Gamow bags, but supply is limited and costs extra. Oxygen buys time but is not a substitute for descent.

Which network works best for emergency calls?

Nepal Telecom (NTC) is most reliable in the Everest and Manaslu regions, while Ncell covers the Annapurna area well. Save your insurer's emergency number offline.

Auditor's Note: All elevations, permit regulations, and logistical data in this guide have been fact-checked against 2026 Nepal Tourism Board and local municipality frameworks for accuracy and safety as of 2026.

Elevation Band	Max Sleep Gain Per Day	Rest Day Rule
Below 3,000 m	Flexible	Not usually needed
3,000–4,000 m	300–500 m	1 rest day per 1,000 m
4,000–5,000 m	300 m	Mandatory rest days
Above 5,000 m	Minimise time spent	Descend to sleep low if possible

Feature	HACE	HAPE
Organ affected	Brain	Lungs
Key symptom	Loss of coordination, confusion	Breathlessness at rest, wet cough
Field test	Walk a straight line (ataxia)	Breathing rate at rest, lip colour
Support drug	Dexamethasone	Nifedipine
Definitive cure	Immediate descent	Immediate descent