Altitude Sickness in Nepal | Complete Guide

Altitude sickness is the single most common medical problem that trekkers face in Nepal. This condition, which doctors also call acute mountain sickness or AMS, happens when your body struggles to adjust because oxygen becomes scarce at high elevation. 

Above roughly 2,500 meters, the air contains far less oxygen than at sea level. Each breath you take delivers only about two-thirds of the oxygen you would get breathing at the beach. 

In fact, when you climb faster than your body can adapt, oxygen levels in your blood fall. Then, your cells begin to suffocate, producing symptoms that we call altitude sickness.

From our internal research, we figured out that roughly one in three visitors who ascend above 3,000 meters experiences at least mild symptoms. 

In fact, experts will tell you that on popular trails such as Everest Base Camp, Annapurna Circuit, and Langtang Valley, these reactions are almost expected unless you ascend slowly and deliberately.

Why Altitude Sickness Happens

At sea level, barometric pressure keeps oxygen molecules packed tightly together. 

As you climb higher, the pressure falls. Each lungful of air carries less oxygen. Your body responds with adjustments that take time to develop properly.

Within minutes to hours, your breathing becomes faster and your heart rate increases. Over the next one to two days, your kidneys begin excreting bicarbonate to balance blood pH. 

Between three to ten days, your body starts producing more red blood cells. The problem occurs when you ascend too rapidly. These adaptations lag behind your climbing speed. This is why your tissues experience hypoxia, which means a shortage of usable oxygen. 

The brain and lungs react by dilating blood vessels, which raises internal pressure. That extra pressure causes small leaks of plasma into surrounding tissue, leading to headache, dizziness, and, if unchecked, life-threatening swelling.

The Three Types of Altitude Illness

All altitude-related problems exist on one continuum, ranging from mild discomfort to organ-threatening conditions. 

The most common of which is Acute Mountain Sickness, which appears six to twelve hours after reaching above 2500 meters. It starts with a dull, throbbing headache comes with nausea, fatigue, or poor sleep.

However, AMS by itself is not dangerous, but if ignored and you continue climbing, it can progress to serious forms.

Then comes High Altitude Pulmonary Oedema, which people call HAPE, a condition of fluid accumulation in the lungs. This usually occurs above 3,000 to 4,000 meters. 

Talking about its first clue, it is breathlessness that worsens even when resting. Left untreated, oxygen transfer fails, and you can drown in your own fluids. 

The other common type of Altitude sickness is High Altitude Cerebral oedema, called HACE, which occurs when your brain swells because of hypoxia. It generally develops above 4,000 meters and follows untreated AMS. 

Symptoms include confusion, loss of coordination, and eventually coma. 

While in the mountains, you need to realise that HACE and HAPE are medical emergencies demanding immediate descent and oxygen. Though frightening, both conditions are preventable. 

In fact, every fatal case in Nepal’s trekking history began with AMS that was ignored or masked by painkillers.

Symptoms Of Altitude Sickness 

Altitude sickness begins subtly. As a matter of fact, our experienced guides insist that any headache at altitude is altitude sickness until proven otherwise. 

Key early symptoms include:

• Headache that worsens with movement
• Loss of appetite
• Unusual tiredness or dizziness 
• Restless sleep or vivid dreams.

However, there are some Serious red flag symptoms that require immediate descent:

• Breathlessness at rest
• A cough that turns wet or produces froth
• Clumsiness or a staggering gait
• Confusion or hallucination
• Blueness of lips or fingertips. 

To be safe, it will be smart to monitor yourself each evening to prevent surprises.

All of our guides always carry a pulse oximeter. Then, if the reading is below 85 per cent at 3,400 meters or below 80 per cent at 4,400 meters, they suggest your body is not keeping up, and it’s a good idea to descend. Remember, there is always another day to ascend to your highest mountain. 

Who Gets Altitude Sickness and Why

Let us first tell you that Altitude sickness respects no fitness level. 

Marathon runners get sick. Sedentary office workers stay healthy. 

Physical fitness does not protect you because the condition is caused by physiological adaptation speed, not cardiovascular strength. However, certain patterns sharply increase your odds. 

One of which is the speed of ascent. Gaining more than 500 meters in sleeping height per day above 3,000 meters dramatically increases AMS risk. 

In fact, as per our experience in the Everest Base Camp trek or Nar Phu Valley, skipping rest days at places like Namche Bazaar or Manang creates major problems. 

Another major factor is that pre-existing heart, lung, or blood disorders make altitude adjustment harder. This is why we advise you to see a doctor before planning your trek in Nepal.

Furthermore, alcohol and sedatives suppress your breathing drive, which also increases the risk of AMS.

Besides that, previous AMS episodes predict future problems with a roughly 60 per cent recurrence rate. 

Last but not least, youthful overconfidence creates unnecessary risk because fit trekkers often ignore symptoms longer. 

In fact, you mightn’t know that even Nepalese locals visiting high passes after living in lowlands can be affected, showing that genetics offer no full protection.

Where Altitude Sickness Strikes Most

Certain points on classic trails are notorious for rapid altitude gain. Here are some examples from Everest and Annapurna: 

The steep climb between Lukla at 2,860 meters and Namche Bazaar at 3,440 meters in a single day often triggers first headaches. 

On the Annapurna Circuit, road access to Manang at 3,519 meters has led many domestic tourists to drive directly there, producing a surge of cases among Nepalis unfamiliar with acclimatisation. The lesson is clear: altitude sickness is preventable through proper acclimatisation.

Prevention and Safe Acclimatisation in Nepal

Every case of altitude sickness is, in essence, a failure of pacing. 

Prevention does not require medical training. It only requires discipline. In Nepal’s Himalayas, where every hour of ascent cuts into available oxygen, prevention means slow, steady travel and intelligent planning. 

Furthermore, the difference between a breathtaking trek and a helicopter evacuation usually lies in whether you respect two truths. 

• First, the human body can adapt to altitude, but only at its own speed. 
• Second, no drug, machine, or fitness level can replace that time.

Designing a Safe Ascent Schedule

A proper itinerary is the single most effective preventive tool. Altitude gain must always lag behind adaptation. The rules are simple and proven by decades of experience.

Treks that respect these limits show up to 60 per cent fewer AMS cases. 

But, short and fast six to seven-day Everest Base Camp packages that skip rest stops at Namche or Dingboche account for most medical evacuations. 

A smart itinerary example for Everest Base Camp would be Day 1 to 2 from Lukla to Namche Bazaar at 3,440 meters with a rest day on Day 2. Day 3 to 4 from Namche to Tengboche at 3,870 meters, then to Dingboche at 4,410 meters with a rest day on Day 5. Day 6 to 8 from Dingboche to Lobuche at 4,940 meters, then to Gorakshep at 5,164 meters. A second rest day at Dingboche halves the risk of AMS beyond 5,000 meters.

How the Body Learns to Breathe Thin Air

When you linger a day at mid altitude, your body runs its own training camp. 

Your breathing rate increases, drawing in more oxygen per minute. Then, Blood pH adjusts as the kidneys excrete bicarbonate to stabilise acidity. 

Additionally, Red blood cells multiply, improving oxygen carriage. Muscle metabolism shifts, relying more on carbohydrates for efficiency. These adaptations together raise oxygen saturation by 3 to 7 per cent within 24 hours. This improvement is enough to turn fatigue into confidence. Skipping that pause steals your safety margin.

Role of Preventive Medication

Medicine supports acclimatisation. But remember that it never replaces it. 

The main options recognised by the CDC, WHO, and Himalayan Rescue Association include acetazolamide, dexamethasone, and medications for people with previous HAPE. 

Acetazolamide, which people know as Diamox, speeds acclimatisation. The prevention dose is 125 mg twice daily, starting one to two days before ascent. Continue for two to three days after reaching your highest sleeping altitude. 

The mechanism creates mild metabolic acidosis that stimulates breathing. 

However, there are side effects that include tingling fingers, frequent urination, and a metallic taste. The contraindication is severe sulfonamide allergy. 

Dexamethasone is used only when rapid ascent is unavoidable or for emergency situations. The dose is 2 mg every 6 hours or 4 mg every 12 hours. This medication reduces brain swelling but does not aid adaptation. 

However, you need to stop taking it as soon as normal ascent resumes. 

On the other hand, medicines like Nifedipine, Sildenafil, and Tadalafil are reserved for people with previous HAPE. They lower pulmonary artery pressure, but should never replace descent if symptoms appear. The short list for easy recall is Diamox equals prevention, Dexamethasone equals emergency, and Nifedipine equals lungs only.

Hydration and Nutrition at Altitude

Dehydration silently worsens AMS because dry mountain air increases fluid loss through breathing. So, target 3 to 5 litres of liquid daily, spacing sips through the day. 

Best choices include water with electrolyte packets or oral rehydration salts, soups and ginger tea and broths with added salt for sodium replacement.

But it’s essential to limit caffeine to moderate levels because too much acts as a diuretic. At altitude, metabolism prefers carbohydrates. 

They yield more energy per unit of oxygen than fats or proteins. In fact, aim for 60 to 70 per cent of calories from carbs, including rice, potatoes, pasta, and lentils.

Sleep and Recovery Is Extremely Important

Sleep quality drops as oxygen falls. Shallow breathing and periodic apnea are common. To improve rest, here are some tips:

• Sleep slightly propped up to ease breathing.
• Keep your tent or room ventilated for fresh air. 
• Avoid sleeping pills and alcohol because they suppress the respiratory drive. 
• Use a warm sleeping bag because cold stress increases oxygen consumption. 

Remember, even experienced guides find that two nights of poor sleep predict AMS the following day. Rest is as vital as hydration.

Physical Preparation Before Your Trek

Yes, we already told you that fitness does not prevent AMS, but it’s also a known fact that a trained body handles stress better. 

Recommended preparation starts six to eight weeks before your trek, which includes 

• Three to four sessions per week of aerobic training, such as hiking, cycling, or stair climbing
• Include long walks with a loaded backpack to build endurance. 
• Train on nearby hills or sleep at a moderate altitude to familiarise your breathing pattern. 
• For urban trekkers, some gyms now offer hypoxic training rooms. Though useful, they only partially simulate real altitude and cannot replace gradual ascent in Nepal’s terrain.

Practical Preparation Checklist

• Before departure, consult a doctor about acetazolamide and general fitness.
• Ensure your travel insurance covers altitude sickness and helicopter evacuation.
• Pack a small medical kit with pain relievers, rehydration salts, and a pulse oximeter.
• Read the HRA booklet called High Altitude Illness in Nepal. 
• On the trail, climb slowly, rest often, and watch for headache or loss of appetite. 
• Use your pulse oximeter each night and record readings. 
• Take rest days even if you feel strong because acclimatisation is preventive, not reactive. 

Remember, the short rule in mountains is to listen to your lungs, not your watch.

Behavioural Tips That Make a Difference

• Walk at a conversation pace. If you cannot talk, you are ascending too fast. 
• Keep layers dry because wet clothes steal energy for rewarming. 
• Protect from sunburn because UV is stronger and can dehydrate you through skin loss. 
• Avoid smoking because carbon monoxide further reduces oxygen uptake. 
• Observe others. Often, your companions spot your fatigue before you do.

Role of Guides and Group Leaders

In the Himalayas, qualified Nepali guides trained by the Himalayan Rescue Association or Nepal Mountaineering Association are your first line of defence. For our guides, we have strictly told them that their responsibilities include: 

• Conducting daily health checks with headache questions and pulse oximeter readings
• Adjusting the itinerary if anyone shows AMS symptoms
• Ensuring team members carry sufficient water and warm gear
• Coordinating with HRA aid posts or helicopter services in emergencies. 

Note: Solo trekking is legal in some regions but discouraged above 3,000 meters because isolation delays rescue. Joining a registered agency like ours dramatically reduces risk.

The Psychology of Slowing Down

Many AMS cases are psychological failures rather than physiological ones. Trekkers fixated on reaching the base camp ignore their bodies out of pride or peer pressure.

Understanding that the mountain will still be there tomorrow is a core safety principle. 

As HRA doctors often say,

Going up is optional, but coming down is mandatory. 

Furthermore, resilience at altitude is not measured by speed but by judgment. So, stopping when necessary is a sign of strength, not weakness.

Treatment and First Aid Response in Altitude Sickness

At any elevation above 2,500 meters, treat every headache as altitude sickness until proven otherwise. 

As a matter of fact, altitude illness moves fast. What begins as a dull ache at Namche Bazaar can, within a day, evolve into life-threatening brain or lung swelling. 

So, you should always keep in mind that prompt action, not heroics, is the cure. 

Stop Ascending Immediately

The first and most critical response to any symptom is to halt further ascent immediately. Climbing higher while symptomatic is the main reason mild AMS turns fatal. This rule has no exceptions.

If the person rests for 24 hours and symptoms improve, ascent can resume slowly. However, when symptoms do not improve or worsen, you must prepare to descend. 

Many trekkers make the mistake of continuing to climb because they feel pressure to keep up with their group, or because they paid for a trek to a specific destination. These reasons are never worth risking your life.

Stabilise at Current Altitude

When symptoms are mild, which means headache plus nausea plus fatigue, rest and hydration often reverse them. 

Remain at the same elevation for at least 24 hours. 

Drink 3 to 5 litres of water daily because dehydration worsens altitude sickness. Eat carbohydrate-rich food to improve oxygen efficiency. 

The truth is your body processes carbohydrates more efficiently than fats or proteins at altitude. 

Besides that, you must absolutely avoid alcohol, smoking, and sleeping pills because they suppress your breathing drive. 

In case the pain increases, use mild pain relievers such as ibuprofen at 400 to 600 mg or paracetamol at 500 to 1000 mg for headache. 

If symptoms ease overnight, you have acclimatised successfully. However, if they worsen, it is time to descend.

Recognise Severity Levels

There are three clinical stages that trekkers should memorise. They are:

1. Mild AMS includes headache plus fatigue or nausea. The correct response is to stop ascent, rest 24 hours, hydrate well, and monitor symptoms every 6 hours. 
2. Moderate AMS includes severe headache, vomiting, and poor coordination. Consider descent within 12 to 24 hours. 
3. Severe AMS, HACE, or HAPE includes ataxia, which means the inability to walk straight, confusion, and breathlessness at rest. Descend immediately by at least 500 to 1000 meters.

The simple checklist for trekkers is this: if you cannot walk in a straight line, descend now. If you cannot count your breaths between steps, descend now. These are emergency situations that require immediate action regardless of time of day or weather conditions.

Medications in the Field

Medication never replaces descent. It buys time to make descent possible. 

Acetazolamide, which people know as Diamox, accelerates acclimatisation. The treatment dose is 250 mg twice daily. Start at the first sign of AMS and continue until symptoms resolve. 

On the other hand, Dexamethasone reduces brain swelling in AMS and HACE. The dose is 8 mg initially, then 4 mg every 6 hours. 

Warning: this provides temporary relief only. Symptoms often rebound if you stay at a high altitude. 

Nifedipine lowers pulmonary artery pressure for HAPE. The dose is 30 mg sustained release every 12 hours. 

Caution: avoid if also suspecting HACE because of hypotension risk. Keep these medicines sealed in waterproof pouches. Carry printed dosage instructions in case others must assist you when you cannot think clearly.

Disclaimer: These are the recommendations of multiple sources. We strongly advise you to consult your guide or medical professional before trying some of these medications. 

Use Oxygen Wisely

Oxygen brings immediate relief, but supplies are finite. Furthermore, at some locations, oxygen mightn’t be available as well. 

However, in case they are available for mild AMS, use 1 to 2 litres per minute to maintain oxygen saturation above 90 per cent while resting. 

On the other hand, for HACE or HAPE, use 2 to 4 litres per minute and continue until descent or stabilisation.

Note: Portable cylinders containing 300 to 600 litres last only 2 to 4 hours at 2 litres per minute. This means you must prioritise descent even while using oxygen.

In the Everest and Annapurna regions, many lodges above 4,000 meters rent oxygen by the hour. HRA aid posts refill bottles for emergencies.

Emergency Descent and Evacuation

When symptoms worsen despite rest, descent is mandatory. 

In such cases, you must descend 500 to 1000 meters immediately, whether day or night. 

Walk if able. Otherwise, arrange porters or animal transport. 

If you are handling someone close, you need to keep the patient warm and semi-upright. Never leave them alone. Oxygen and dexamethasone should continue during descent. 

If descent is impossible because of storm, terrain, or darkness, use a portable hyperbaric chamber called a Gamow bag. It simulates a 1,000 to 3,000-meter descent by increasing air pressure inside the bag. One session lasts 1 to 2 hours. Symptoms improve rapidly but return when the bag is opened, so descend as soon as conditions allow.

Note: We have trained our guide to handle these kinds of situations well. Trust their judgment in case of an emergency. 

Helicopter Evacuation in Nepal

Helicopter rescue is routine along major trekking corridors. 

From Gorakshep to Kathmandu takes roughly 45 to 90 minutes, depending on the weather. Average cost ranges from USD 4,000 to USD 6,000, so confirm your insurance covers helicopter evacuation before your trek. 

Major operators coordinate directly with CIWEC Hospital or the Himalayan Rescue Association in Kathmandu once notified. 

Additionally, provide the patient’s name, the exact location with GPS coordinates if possible, and a visible landmark. Trekkers without insurance can request group pooling. Guides often combine multiple patients to split flight costs.

Medical Support Posts on the Trails

Nepal’s mountain safety network has grown remarkably since the 1970s.

In fact, the Himalayan Rescue Association operates aid posts at Pheriche at 4,243 meters in the Everest Region and Manang at 3,519 meters on the Annapurna Circuit. 

Also, the Everest ER at 5,300 meters operates at the Everest Base Camp but only during the spring season. 

Furthermore, each post is staffed by volunteer doctors offering consultation, oxygen, and Gamow bags. 

We advise you to attend their daily lectures at 4 PM, which teach altitude awareness to hundreds of trekkers per season. 

Talking about the Nearest city hospitals for definitive care, they are:

•  CIWEC Hospital in Kathmandu
• Norvic International Hospital in Kathmandu
• Manipal Teaching Hospital in Pokhara. 

Quick Decision Guide

When in doubt, follow this sequence. 

• First, recognise that headache plus fatigue means suspect AMS. 
• Second, rest with no ascent for 24 hours. 
• Third, reassess: if improved, continue slowly; if worse, descend. 
• Fourth, rescue with oxygen, medication, or a helicopter as needed. 

The simple way to remember this is the 4 Rs: Recognise, Rest, Reassess, Rescue.

Managing Fear and Judgment

Panic is as dangerous as denial. 

In fact, fear may cause rushed decisions, and pride may cause fatal delay. 

In case of emergency, trust your guide and the data from your own body. 

Many trekkers evacuated for severe AMS return a year later and complete their goal safely by climbing more slowly. Remember that every experienced climber has turned back at least once. The mountain rewards patience, not speed

Recovery and Long-Term Effects of Altitude Sickness

The moment you descend below about 1,500 meters, oxygen pressure rises enough that symptoms often disappear within 12 to 48 hours. 

The good news is that the Headache fades first, appetite returns, and urine output normalises as the kidneys rebalance fluids. 

For most trekkers, no hospital stay is required. You only need rest, hydration, and calories. 

Even after recovery, however, the body remains physiologically tired. It can take several days for red blood cell mass, acid-base balance, and sleep patterns to settle.

The rule of thumb is this: for every day spent above 4,000 meters, allow one day of full rest after coming down.

Recovery Timelines by Condition

Different severity levels require different recovery periods.

Mild AMS leaves no trace. But severe pulmonary or cerebral oedema can cause transient inflammation and fatigue for weeks, even after discharge from the hospital. 

This is why proper treatment and adequate rest matter so much.

Neurological and Pulmonary After Effects

Although rare, untreated altitude illness can leave measurable effects. The brain can experience short-term memory issues, concentration difficulty, or mood changes that persist for days after HACE. 

In fact, MRI studies on climbers have shown small, reversible lesions in the corpus callosum and white matter tracts. These indicate microedema rather than permanent damage. 

Full cognitive recovery is expected within 2 to 4 weeks if descent and oxygen were prompt. The lungs after HAPE may remain mildly stiff or congested for several days. 

Additionally, a cough can linger for up to two weeks, but gradually clears. 

And the Chest X-ray normalises once the interstitial fluid reabsorbs. Doctors recommend no re ascent for at least 7 days after HAPE or HACE. Get a follow-up with a chest or neurological exam before attempting altitude again.

Post-Treatment Medical Follow-Up

In Kathmandu or Pokhara, patients are generally evaluated at CIWEC Hospital or Norvic International within 24 hours of evacuation. Evaluation typically includes:

• An oxygen saturation test at rest and exertion
• Chest auscultation for residual crackles, which indicate HAPE
• A basic neurological exam for HACE
• Blood test for hematocrit and electrolytes. 

If results are normal, doctors clear travellers for low altitude flights home within 2 to 3 days. However, for severe cases, oral acetazolamide may continue for another 24 hours to assist diuresis and normalise acid-base balance.

Restoring Physical Balance

After a high altitude illness, focus on replenishment through several key areas. 

The first key area that you need to focus on is hydration because lost fluids during illness can reach 3 to 5 litres per day through hyperventilation. Replace gradually with water, soups, and electrolyte solutions. 

Talking about nutrition, it requires high-carbohydrate meals to help restore glycogen and ease recovery. Add iron-rich foods like lentils, spinach, and red meat to rebuild blood volume. 

Besides that, sleep quality indicates recovery progress. Return of deep, restorative sleep signals full recovery. Avoid caffeine and maintain dark, quiet surroundings. 

In addition to that, light exercise through gentle walking on flat terrain promotes circulation. Avoid strenuous climbs for a week after symptoms resolve.

When Complications Persist

If cough, shortness of breath, or confusion continue after two days at low altitude, it may indicate residual infection or fluid accumulation. Possible complications include post-HAPE pneumonia, which is bacterial superinfection, residual cerebral oedema, and dehydration or electrolyte imbalance. 

Medical imaging or oxygen therapy may be required. Such prolonged cases are uncommon among trekkers who descend promptly. Most people who descend at the first sign of serious symptoms recover completely without complications.

Psychological and Emotional Impact

Many rescued trekkers describe feelings of guilt, failure, or fear about returning to the mountains. This reaction is normal because altitude illness can be traumatic. 

Coping strategies for this scenario include debriefing with guides and doctors to understand what happened, sharing experiences publicly because educating others reinforces confidence, and reframing recovery as success because you made the right choice in descending. 

Remember, most climbers who process their event rationally return stronger the next season. Understanding that descent shows wisdom, not weakness, helps with emotional recovery.

Re-Ascent and Future Trek Planning

Having altitude sickness once does not mean you can never trek again. It means you must respect altitude more. 

As a matter of fact, the body learns from experience. Rules for safe return include:

• Waiting at least two weeks after complete recovery before reascending
• Climbing slower by adding extra rest days and avoiding direct road access to 3,000 meters, 
• Beginning preventive acetazolamide early at 125 mg twice daily
• Carrying a pulse oximeter plus oxygen if previous HAPE or HACE occurred
• Inform your guide about your prior episode so they can monitor you more closely.

Long term, many patients show improved awareness and become the best high altitude trekkers because they understand their limits.

Chronic Mountain Sickness

While trekkers experience acute altitude illness, permanent residents above 3,500 meters sometimes develop Chronic Mountain Sickness, which doctors also call Monge’s Disease.

It is marked by excess red blood cell production with hematocrit above 65 per cent, cyanotic lips with headaches and fatigue at rest, and enlargement of the right heart from high pulmonary pressure. CMS is extremely rare among visitors. It develops only after years of continuous residence. This helps readers understand the spectrum of altitude physiology in Nepal’s highlands.

Returning to Trekking

Guides across Khumbu and Annapurna repeat the same advice to returning trekkers. The mountain rewards patience. If you felt weak last time, walk more slowly next time. Altitude does not remember your pride, only your pace. 

This wisdom, combined with medical knowledge, prevents recurrence. Every successful re ascent story in Nepal starts with humility learned from the first illness. 

In our recent memory, there was a 35-year-old trekker with us who developed HAPE at Lobuche at 4,940 meters. He received oxygen, nifedipine, and a helicopter evacuation to Kathmandu. 

Within 48 hours at 1,300 meters, symptoms resolved. One month later, he reattempted Everest Base Camp with a slower 12-day itinerary and acetazolamide prophylaxis and reached Base Camp safely. Such stories illustrate that altitude illness, though serious, need not end your Himalayan dream. Knowledge transforms fear into preparation.