Altitude Sickness on the Everest Base Camp Trek: Prevention and Symptoms

It often starts quietly—a dull headache after arriving in Dingboche.   plate of dal bhat you suddenly do not feel like eating—a night spent lying awake, breathing in short gasps, listening to the wind. For most trekkers, these signs pass with rest, water, and time. F r a few who ignore them, they become the start of something far more dangerous.

Altitude sickness on the Everest Base Camp Trek is the single biggest reason trekkers turn back before reaching base camp, and in rare cases it can be life-threatening. The good news is that it is also largely preventable. With the right itinerary, an understanding of the warning signs and the willingness to listen to your body, most trekkers reach Everest Base Camp safely.

In this guide, our Sherpa team explains everything you need to know about altitude sickness on the Everest Base Camp Trek: why it happens, where on the trail the risk is greatest, the symptoms of AMS, HAPE and HACE, how to prevent it, what to do if it strikes and how our team keeps trekkers safe on our Everest Base Camp Trek. This article is general information, not medical advice; always talk to your doctor before travelling to high altitude.

Altitude Sickness at a Glance

• What it is: A group of illnesses caused by ascending to high altitude faster than the body can adapt to lower oxygen levels.
• Main forms: Acute mountain sickness (AMS), high-altitude pulmonary oedema (HAPE) and high-altitude cerebral oedema (HACE).
• Where it can start: Above about 2,500 m, on the Everest trail, risk rises noticeably above Namche Bazaar at about 3,440 m.
• Highest-risk section: Dingboche, Lobuche and Gorakshep, between about 4,400 and 5,200 m, and the climbs to Everest Base Camp and Kala Patthar.
• Who it affects: Anyone, regardless of age, gender or fitness.
• Main prevention: Gradual ascent, acclimatisation days, hydration and honest communication.
• Main treatment for serious cases:

Why Altitude Sickness Happens

High-altitude air contains the same percentage of oxygen as at sea level, but the air pressure is much lower, so each breath delivers less oxygen to your body. At Eve est Base Camp, at 5,364 m, the effective oxygen available is roughly half of what you breathe at sea level.

Your body adapts to this over days and weeks. You breathe faster and deeper, your heart rate increases, and over time your body produces more red blood cells to carry oxygen. This process, called acclimatisation, takes time. Altitude sickness happens when you climb faster than your body can adjust.

Sleeping Altitude Matters Most

Medical experts emphasise that the altitude at which you sleep matters more than the highest point you reach during the day. That’swhy the classic advice is to “climb high, sleep low”: hike higher during the day to stimulate adaptation, then return to sleep at a lower altitude.

Fitness Does Not Protect You

One of the most important facts about altitude sickness on the Everest Base Camp Trek is that physical fitness does not prevent it. Young, fit athletes can be affected just as easily as older or less fit trekkers, and sometimes more so, because they tend to walk too fast. What protects you is the pace of ascent, not the strength of your legs.

The Altitude Profile of the Everest Base Camp Trek

Understanding how altitude increases along the trail helps you see where the risks lie. These are approximate sleeping altitudes on a typical itinerary:

• Kathmandu: About 1,400 m.
• Lukla: About 2,860 m, reached by a short flight. This sudden gain is one reason the first nights matter.
• Phakding: About 2,610 m, slightly lower than Lukla, giving your body a gentle start. See our guide to Phakding and Monjo.
• Namche Bazaar: About 3,440 m, a gain of over 800 m from Phakding, so an acclimatisation day here is essential. Read about Namche Bazaar.
• Tengboche or Deboche: About 3,860 m. See our Tengboche
• Dingboche: About 4,410 m, the site of the second acclimatisation day. See our Din boche
• Lobuche: About 4,910 m. See our Lobuche
• Gorakshep: About 5,164 m, the highest sleeping point. See our Gorakshep
• Everest Base Camp: 5,364 m, visited during the day.
• Kala Patthar: About 5,545 m, the highest point of the trek, usually climbed at sunrise. Read ur Kala Patthar.

Medical guidelines generally recommend that, above about 3,000 m, trekkers avoid increasing their sleeping altitude by more than around 500 m per day where possible, and take an extra acclimatization day for roughly every 1,000 m gained. A good Everest itinerary follows this pattern as closely as the geography allows, with rest days at Namche and Dingboche. Our E erest Base Camp Trek itinerary follows these principles.

Acute Mountain Sickness (AMS)

AMS is the most common form of altitude sickness on the Everest Base Camp Trek. Many trekkers experience at least mild symptoms at some point, particularly after arriving in Namche, Dingboche or Lobuche.

Symptoms of AMS

The main symptom is a headache, usually accompanied by one or more of the following:

• Loss of appetite or nausea, sometimes with vomiting.
• Unusual tiredness or weakness.
• Dizziness or light-headedness.
• Difficulty sleeping, often waking frequently or feeling short of breath at night.

Many people describe mild AMS as feeling like a bad hangover. Sympt ms usually appear six to twelve hours after arriving at a new altitude.

What to Do About Mild AMS

• Stop ascending: Do not go higher until your symptoms have fully resolved.
• Rest: Take it easy at the same altitude and keep activity light.
• Hydrate: Drink plenty of fluids, but do not force excessive amounts.
• Eat: Keep eating, even if your appetite is low.
• Pain relief: Simple painkillers can help with headaches, as your doctor advises.
• Tell your guide: Your guide will monitor you closely.

Mild AMS often improves within a day or two of rest. If symptoms worsen despite rest, or if new symptoms appear, descend.

Moderate to Severe AMS

Severe AMS includes a headache that does not respond to painkillers, repeated vomiting, marked weakness and worsening fatigue. This indicates the body is not coping and that descent is needed. Severe AMS can progress to HACE.

High Altitude Cerebral Oedema (HACE)

HACE is brain swelling caused by altitude. It is less common than AMS but is a life-threatening emergency. It usually develops from worsening AMS, often at higher altitudes such as Lobuche and Gorakshep.

Symptoms of HACE

• Loss of coordination: Stumbling, swaying or difficulty walking in a straight line. This is the key warning sign.
• Confusion or changes in behaviour: Irritability, unusual quietness, difficulty answering simple questions or irrational decisions.
• Severe headache that does not improve with painkillers.
• Drowsiness that progresses towards unconsciousness.
• Nausea and vomiting.

The Heel-to-Toe Test

A simple field test for HACE is to ask the person to walk heel to toe along a straight line, as in a sobriety test. If they cannot do this without stumbling, and they are not simply exhausted, assume HACE and act immediately. Our guides use this test whenever they are concerned about a trekker.

What to Do About HACE

• Descend immediately: Even a few hundred metres can help. Do not wait until morning if it is possible to move safely.
• Never leave the person alone.
• Use oxygen if available.
• Seek medical help: Contact the nearest health post or arrange helicopter evacuation.

HACE can become fatal within hours if untreated. Speed matters.

High Altitude Pulmonary Oedema (HAPE)

HAPE is fluid in the lungs caused by altitude. It can develop with or without AMS symptoms, which makes it particularly important to recognise. It is also a life-threatening emergency.

Symptoms of HAPE

• Breathlessness out of proportion to effort: Struggling to keep up, needing to stop far more often than others.
• Breathlessness at rest: Feeling short of breath even when lying still.
• A persistent cough: Starting dry and later producing frothy or pink-tinged sputum.
• Gurgling or crackling sounds when breathing.
• Extreme fatigue and weakness.
• Bluish lips or fingertips in more advanced cases.
• Chest tightness or a fast heart rate.

What to Do About HAPE

• Descend as soon as possible, minimising exertion; the person should walk slowly or be carried or flown.
• Use oxygen if available.
• Keep warm and rest, sitting upright rather than lying flat.
• Seek medical help and arrange evacuation if needed.

HAPE responds very well to descent and oxygen if caught early. Many trekkers recover quickly once they reach lower altitude.

Where Altitude Sickness Is Most Likely on the Everest Trail

Based on our guides’ experience and the pattern of medical cases in the region, these are the places where trekkers most often feel the effects of altitude:

Namche Bazaar

After a big climb from the Hillary Bridge, many trekkers arrive in Namche and feel their first mild headache. This i  why we always include an acclimatization day here, with a hike to the Hotel Everest View and Khumjung and Khunde.

Dingboche and Pheriche

Above the tree line, around 4,200 to 4,400 m, the thinner air becomes very noticeable. This is our second acclimatisation day. Pheriche, a short walk away, is home to the Himalayan Rescue Association aid post, where volunteer doctors treat altitude illness during the trekking seasons and give daily talks on prevention. Read our guide to Pheto, the HRA aid post.

Lobuche and Gorakshep

This is the highest-risk section of the trek. Sleeping altitudes rise above 4,900 m and then to over 5,100 m, where sleep is difficult, appetite drops, and the cold adds stress. Most serious cases of altitude illness on the trek develop here. Our guides monitor every trekker closely in these villages.

Everest Base Camp and Kala Patthar

The long day to base camp and the pre-dawn climb to Kala Patthar take you to the trek’s highest altitudes. Fatigue, cold, and dehydration all increase the risk. If anyone in the group shows signs of altitude illness, our guides will turn back before these climbs.

How to Prevent Altitude Sickness on the Everest Base Camp Trek

Prevention is far better than cure. These are the most important ways to avoid altitude sickness on the Everest Base Camp Trek:

Choose a Well-Paced Itinerary

Your itinerary is the most important decision you make. Avoid rushed itineraries that skip acclimatisation days to save time. A good itinerary includes at least two acclimatisation days, at Namche and Dingboche, and limits daily increases in sleeping altitude where possible.

Climb High, Sleep Low

Use acclimatisation days actively. Hike a few hundred metres higher during the day and return to sleep lower. In Namche, hike to Syangboche and Khumjung; in Dingboche, climb towards Nangkartshang Peak or walk towards Chhukung.

Walk Slowly

Sherpas say “bistari, bistari,” meaning slowly, slowly. Walk at a pace where you can still talk comfortably. Excitement on th first days often leads trekkers to walk too fast.

Stay Hydrated

Dry air and heavy breathing at altitude cause significant fluid loss. Drink regularly throughout the day, about three to four litres, including soups and teas. Your urine should be pale. However, drinking excessive amounts does not prevent altitude sickness and can cause other problems.

Eat Well

Your body needs energy to acclimatise. Eat regular meals with plenty of carbohydrates, such as rice, potatoes, noodles, and bread, even when your appetite drops.

Avoid Alcohol and Sleeping Pills

Alcohol dehydrates you and can depress breathing during sleep, making altitude symptoms worse. Sleeping pills can also suppress breathing at night. Avoid both while ascending.

Keep Warm and Sleep Well

Cold adds stress to your body and disrupts sleep. A warm sleeping bag, warm layers and a hot water bottle at night help you rest and recover. Our Everest Base Camp Trek packing list explains what to bring.

Know Your History

If you have suffered altitude sickness before, especially HAPE or HACE, tell your doctor and your guide. You may be at higher risk and may need a slower itinerary or preventive medication.

Communicate Honestly

The most dangerous thing a trekker can do is hide symptoms to keep up with a group or reach a goal. Tell your guide every morning and evening how you feel. Catching small problems early makes them easy to manage.

Preparing Before You Leave Home

Preventing altitude sickness on the Everest Base Camp Trek begins long before you land in Lukla:

• See your doctor: Discuss your health, any medications you take, your previous experience at altitude and whether preventive medication is appropriate. A travel clinic or a doctor familiar with mountain medicine is ideal.
• Train your body: Good fitness will not prevent altitude sickness, but it makes long days easier, so you have more energy to recover. Our beginner guide to the Everest Base Camp Trek includes a simple training plan.
• Choose the right season: Stable weather and comfortable temperatures reduce stress on your body. Read our guide to the best time for the Everest Base Camp Trek, including our Everest Base Camp Trek in October guide.
• Plan buffer days: Extra days let you rest if needed, rather than pushing on to make a flight.
• Arrange insurance: Make sure your policy covers high-altitude trekking and helicopter evacuation. Pre-acclimatisation: Some trekkers use altitude tents or hypoxic training at home.  Evidence for these methods is mixed, and they are no substitute for a well-paced itinerary on the trail.

A Day-by-Day Altitude Checklist on the Trail

Here is how our guides think about altitude at each stage of the trek:

• Lukla and Phakding: Altitude is moderate, but you have just flown up from Kathmandu.  Start slowly, drink well and avoid alcohol.
• Namche Bazaar: Expect to feel the altitude on arrival. Use the acclimatisation day for a gentle hike higher, then rest.
• Tengboche and Deboche: The forests and monastery make this a wonderful place to rest and recover. Read our guide to Tengboche Monastery and the Mani Rimdu festival.
• Pangboche to Dingboche: You cross the tree line and climb above 4,000 m. Walk slowly and stop at the old monastery in Pangboche for a rest.
• Dingboche acclimatisation day: Climb a few hundred metres higher and return to sleep. Report any symptoms honestly to your guide.
• Thukla and Lobuche: The steep climb to the Thukla Pass memorials is a tough moment. Take it slowly and keep drinking.
• Gorakshep, base camp and Kala Patthar: The highest and hardest days. If anyone in the group shows signs of HACE or HAPE, the group turns back immediately.
• Descent: Most symptoms improve quickly as you descend. Many trekkers feel strong and hungry again once they reach Pheriche or Namche.

Recognising Altitude Sickness in Others

People with altitude sickness are not always the best judges of their own condition. Confusion, tiredness and the desire to reach a goal can cloud judgment. Watch your trekking companions for these signs:

• Unusually slow walking or frequent stops compared with their normal pace.
• Withdrawal, irritability or unusual quietness.
• Stumbling, poor balance or difficulty with simple tasks such as tying boots.
• Not eating at mealtimes, or vomiting.
• A persistent cough or noisy breathing at rest.

If you notice these signs, tell your guide immediately. Looking after each other is one of the most important parts of trekking safely in the Himalaya.

Pulse Oximeters: Useful, but Not the Whole Story

Many guides and trekkers carry a small pulse oximeter, a fingertip device that measures blood oxygen saturation. Readings naturally fall as you climb, and low readings at high altitude are normal. The numbers can be a useful additional tool, especially when they change sharply or are combined with symptoms. However, they should never replace careful attention to how a person feels and behaves. A trekker with normal-looking readings but worsening headache, confusion or breathlessness still needs to rest or descend.

Medication for Altitude Sickness

Medication can help prevent and treat altitude sickness, but it is not a substitute for a sensible itinerary. Always consult a doctor, ideally one familiar with travel or mountain medicine, before your trip.

• Acetazolamide (often known by the brand name Diamox): The most widely used medication for preventing AMS. It helps the body acclimatise faster. Doctors may recommend it for trekkers at moderate or high risk, such as those with a previous history of AMS or those on faster itineraries. It can cause side effects such as tingling in the fingers and toes and increased urination, and it is not suitable for people with certain allergies.
• Other medications: Doctors may prescribe other drugs for treating severe AMS, HACE or HAPE, or for preventing HAPE in people with a previous history. These are for medical use and should only be taken under guidance.
• Painkillers: Simple painkillers can help with altitude headaches but do not treat the underlying problem.
• Unproven remedies: Many supplements and herbal remedies are marketed for altitude sickness, but most lack good evidence. Garlic soup, a trail favourite, is comforting and hydrating, but it is not a medical treatment.

Never use medication to keep climbing while you have symptoms. If you feel unwell, stop ascending.

The Golden Rules of Altitude Sickness

Our guides teach every trekker these simple rules, which mountain medicine organisations around the world recognise:

• Rule 1: If you feel unwell at altitude, assume it is altitude sickness until proven otherwise.
• Rule 2: Never ascend with symptoms of altitude sickness.
• Rule 3: If symptoms worsen, descend immediately.
• Rule 4: Never leave someone with altitude sickness symptoms alone.

Following these rules saves lives every season in the Himalaya.

How Our Team Keeps Trekkers Safe

Safety is at the heart of every trek we operate. Here is how our team manages altitude risk on the Everest Base Camp Trek:

• Well-paced itineraries: We include acclimatisation days in Namche and Dingboche, plus optional extra days for slower acclimatizers.
• Experienced guides: Our Sherpa guides are trained in first aid and altitude awareness and have years of experience recognising early signs of illness.
• Daily health checks: Guides check on every trekker morning and evening, asking about headaches, appetite, sleep and energy. Many guides also carry a pulse oximeter, but symptoms always matter more than numbers.
• Flexible plans: If someone needs an extra rest day, we adapt the itinerary.
• Descent plans: Guides know where to descend and how quickly, and they never push trekkers to continue when it is unsafe.
• Emergency support: Our Kathmandu office coordinates helicopter evacuation when needed.

Meet the people who lead our treks on our Our Team page, and read our general Acute Mountain Sickness guide for more background.

Helicopter Evacuation and Travel Insurance

In serious cases of altitude sickness, a rapid helicopter descent can be lifesaving. In good weather, helicopters can reach most villages on the Everest trail and fly patients to Lukla or Kathmandu for treatment.

Because of this, travel insurance covering trekking up to at least 6,000 m and helicopter evacuation is essential for every trekker. Make sure your policy clearly covers high-altitude trekking in Nepal, and carry the policy number and emergency contact details to share with your guide. Without proper insurance, arranging evacuation and treatment can quickly be difficult.

Medical Facilities on the Everest Trail

The Everest region has better medical support than most remote trekking areas:

• Lukla: A small hospital and clinics near the airport.
• Namche Bazaar: A health post and pharmacies.
• Khunde Hospital: Founded by Sir Edmund Hillary’s Himalayan Trust, above Namche.
• Pheriche: The Himalayan Rescue Association aid post, staffed by volunteer doctors in the main trekking seasons.
• Everest Base Camp: A seasonal medical clinic during the spring climbing season.

Even so, the most important medical tool on the trail is early recognition and descent, which is why experienced guides are so valuable.

Altitude Sickness and Different Trekkers

Older Trekkers

Age alone does not increase the risk of altitude sickness, and older trekkers often walk more slowly and listen to their bodies better. However, pre-existing health conditions are more common, so a medical check-up before the trek is especially important.

Young and Fit Trekkers

Young, fit trekkers sometimes have a higher rate of problems because they walk too fast and push through symptoms. Fitness helps with the physical effort, but it doesn’t speed up acclimatisation.

Children and Teenagers

Children can be harder to assess because they may not describe symptoms clearly. Families with young children may prefer lower routes such as the Everest View Trek, which stays below about 3,900 m.

Trekkers With Medical Conditions

People with heart or lung disease, high blood pressure, sickle cell disease or other significant conditions should seek specialist medical advice before travelling to high altitude.

Itinerary Options That Reduce Altitude Risk

Some routes and trek styles naturally reduce the risk of altitude sickness on the Everest Base Camp Trek:

• The historic approach: The Jiri to Everest Trek starts in the lower hills, giving a week of gradual acclimatisation before Namche. Read our Jiri to Everest Base Camp trek guide.
• Road access: The Everest Base Camp Trek by Road avoids the sudden altitude gain of the flight to Lukla.
• Comfortable lodges: Better sleep aids acclimatisation. The Everest Base Camp Luxury Lodge Trek uses the best lodges available.
• Helicopter return: The Luxury Everest Base Camp Trek with Helicopter Return reduces the total time spent at high altitude.
• Mindful trekking: The Everest Base Camp Yoga Trek includes breathing practice and a relaxed pace.
• Lower alternatives: The Ghorepani Poon Hill Trek offers mountain views at much lower altitude.

A Note on Helicopter Tours

Helicopter tours such as the Everest Helicopter Tour fly you from Kathmandu to high altitude within an hour. Because you have little time to acclimatise, high-altitude landings are kept very short. If you feel dizzy or unwell during a stop, tell the crew immediately. Read our guide to the Everest Base Camp helicopter tour for more.

Altitude Sickness on Other Everest Region Treks

The same principles apply to every high trek in the region:

• Gokyo Lakes Trek: Acclimatise in Namche and Machhermo before Gokyo and Gokyo Ri. Compare the viewpoints at Gokyo Ri and Kala Patthar.
• Everest 3 Pass Trek: Three passes above 5,300 m, including the Cho La Pass, require excellent acclimatisation and extra rest days.
• Peak climbing: Island Peak, Lobuche Peak, and Ceach are above 6,000 m and require thorough acclimatisation, usually after visiting Everest Base Camp.

How Sherpas Adapt to Altitude

Trekkers often marvel at how easily Sherpa guides and porters move at high altitude, carrying heavy loads up steep trails while visitors stop to catch their breath. Sherpas have lived in the Khumbu Highlands for generations, and research on high-altitude populations in the Himalaya shows they have developed physiological adaptations that help them use oxygen efficiently at altitude.

Even so, Sherpas are not immune to altitude sickness, especially when they return to high altitude after time spent in the lowlands. Their real advantage, beyond genetics, is experience: they know the warning signs, respect the mountains and understand that turning back is never a failure. Learn more about their way of life in our guide to Sherpa culture and traditions, and about the high-altitude environment they call home in our guide to Sagarmatha National Park.

Altitude Sickness on Other Treks in Nepal

The lessons of the Everest trail apply to high treks throughout Nepal. Some routes involve rapid altitude gains or high passes, where the same golden rules are essential:

• Annapurna Circuit Trek: Acclimatise in Manang before crossing the Thorong La at about 5,416 m.
• Manaslu Circuit Trek: Rest in Samagaon or Samdo before crossing the Larke Pass.
• Langtang Gosaikunda Trek: The climb to the sacred lakes gains altitude quickly from the valley below.
• Annapurna Base Camp Trek: Lower than Everest Base Camp, but mild altitude symptoms are still common near the sanctuary.

Common Myths About Altitude Sickness

• Myth: Fit people do not get altitude sickness. Fact: Fitness does not protect you.
• Myth: If I did not get sick last time, I will not get sick this time. Fact: Susceptibility can vary from trip to trip.
• Myth: Drinking huge amounts of water prevents it. Fact: Staying hydrated helps, but drinking too much water does not prevent altitude sickness.
• Myth: Garlic soup cures it. Fact: It is a comforting, hydrating meal, but not a treatment.
• Myth: Medication lets you ascend faster safely. Fact: Medication can help, but it is not a substitute for a gradual ascent.
• Myth: A headache is normal at altitude, so ignore it. Fact: A headache can be the first sign of AMS. Monitor it and tell your guide.

Frequently Asked Questions About Altitude Sickness on the Everest Base Camp Trek

At what altitude does altitude sickness start on the Everest trek?

Altitude sickness can start above about 2,500 m, but on the Everest trail, symptoms are most common above Namche Bazaar, especially at Dingboche, Lobuche and Gorakshep.

How common is altitude sickness on the Everest Base Camp Trek?

Mild symptoms such as headaches are common. Serious altitude illness is much rarer and can usually be prevented with a well-paced itinerary and early recognition of symptoms.

What are the first signs of altitude sickness?

A headache combined with loss of appetite, nausea, tiredness, dizziness or poor sleep.

What should I do if I get altitude sickness?

Stop ascending, rest, hydrate and tell your guide. If symptoms worsen, or if you have signs of HACE or HAPE, descend immediately and seek medical help.

Can I take Diamox for the Everest Base Camp Trek?

Many trekkers use acetazolamide (Diamox) under medical guidance. Talk to your doctor before your trip about whether it is right for you.

Does fitness prevent altitude sickness?

No. Fitness helps with the physical effort of trekking, but it does not prevent altitude sickness. The pace of ascent is what matters most.

Why are acclimatisation days important?

They give your body time to adapt to lower oxygen levels before climbing higher, greatly reducing the risk of altitude sickness.

Is there medical help on the Everest Base Camp Trek?

Yes. Health posts are in Lukla and Namche, the Khunde Hospital, the Himalayan Rescue Association aid post in Pheriche, and helicopter evacuation for emergencies.

What is the difference between AMS, HAPE and HACE?

AMS is the common, usually mild form with headache and nausea. HAPE is fluid in the lungs, causing breathlessness and cough. HACE is brain swelling that causes confusion and loss of coordination. HAPE and HACE are emergencies.

Do I need travel insurance for altitude sickness?

Yes. Your insurance must cover trekking up to at least 6,000 m and helicopter evacuation.

Final Thoughts: Respect the Altitude, Reach the Summit of Your Dreams

Altitude sickness on the Everest Base Camp Trek is real, but it does not have to stop you. Walk slowly, follow a well-paced itinerary, drink plenty of water, sleep warm, and, above all, listen to your body and your guide. The mountains reward patience, and those who respect the altitude stand at Everest Base Camp with a smile.

Our Sherpa team puts your safety first on every step of the journey. Join our classic Everest Base Camp Trek, choose the comfort of the Everest Base Camp Luxury Lodge Trek, or read our guide to Everest Base Camp Trek difficulty to prepare further. Plan your trip or contact us today, and trek to Everest safely with experienced guides by your side.