Tips to Prevent Altitude Sickness in Nepal During Treks

What is Altitude Sickness?

Ever felt like your head’s about to explode just because you climbed a hill too fast? Alright then- you’ve just met altitude sickness, also known as Acute Mountain Sickness (AMS). It occurs due to lower oxygen availability at high altitudes, affecting anyone regardless of fitness level, and can progress to life-threatening conditions like HAPE and HACE above 3,000 meters. If you’re planning a high-altitude adventure, then knowing a few tips to prevent altitude sickness while trekking can save your trip. These tips include ascending slowly, staying hydrated, resting when needed, and proper acclimatization. Altitude sickness happens when your body can’t adjust to the environment with the drop in oxygen levels at higher elevations, typically above 2,500 meters. 

Anyone can get altitude sickness- even marathon runners and yoga instructors. But it’s more common among those who usually live at lower altitudes, ascend rapidly, or have never trekked to the higher altitudes. Factors like dehydration, overexertion, alcohol intake, and skipping rest days can increase the risk. Whether you’re hiking the Himalayas like the Everest Base Camp trek or tall hills, understanding the primary causes of altitude sickness and knowing the preventive measures helps you to complete your trek smoothly.

Altitude Sickness: Myth vs Fact

• Myth: Being physically fit prevents altitude sickness.
  • Reality: Fitness does not protect against AMS; only proper acclimatization does.
• Myth: Alcohol helps you sleep at high altitudes.
  • Reality: Alcohol worsens dehydration and disrupts breathing, increasing AMS risk.
• Myth: Drinking less water reduces bathroom trips at night.
  • Reality: Dehydration increases AMS risk; aim for 3-4L daily with clear urine.
• Myth: Oxygen cans are all you need to stay safe at high altitudes.
  • Reality: They might feel cool for selfies, but they can’t replace proper acclimatization or medical treatment.
• Myth: Locals never get altitude sickness, so you won’t either.
  • Reality: Even locals can get AMS if they ascend too quickly. Altitude doesn’t choose a specific person.

Common types of Altitude Sickness 

Acute Mountain Sickness (AMS)

Acute Mountain Sickness is the common form of altitude sickness, which mostly affects those trekkers who go to high altitudes too quickly. It usually occurs at elevations above 2,500 meters (8,200 feet), and can affect anyone, no matter their age, gender, or fitness level. AMS is caused by low oxygen levels at high altitude and normally shows up to 6 to 24 hours after arriving at a higher elevation. It often shows its symptoms when you climb rapidly, don’t drink enough water, skip rest days, or push your body too hard without giving time to adjust. Consult with the guide as soon as possible to prevent AMS if you suspect any of the symptoms listed below in the table.

High Altitude Pulmonary Edema (HAPE)

HAPE is a severe and nearly life-threatening form of altitude sickness. It occurs when fluid leaks into the lungs due to low oxygen pressure at high elevations, usually above 3,000 meters (9,800 feet). It is caused due to rapid ascent without proper acclimatization, which will be even worse due to cold temperatures, physical overexertion, or continuing the climb despite feeling unwell. Its symptoms usually appear 2-4 days after reaching high altitude and may occur suddenly at night or after a hard climb. HAPE can affect anyone, but it is more likely to affect those who ignore the signs of AMS, ascend too quickly, or have a history of altitude illness. If you don’t treat it soon, it can become fatal, so immediate descent is important at the first sign of symptoms. Here is a list of symptoms of HAPE in the table below:

Note: Blue or gray lips/fingertips are only the symptoms of HAPE, not HACE.

High Altitude Cerebral Edema (HACE)

High Altitude Cerebral Edema is the most dangerous and deadly form of altitude sickness, caused by the swelling in the brain due to a lack of oxygen at high elevations, typically above 4,000 meters (13,000 feet). This swelling puts higher pressure on the brain, leading to confusion, loss of coordination, and coma in some serious cases. It often develops when trekkers ignore AMS or HAPE, climb too quickly, or push forward even though after feel unwell. HACE can appear 2-4 days after reaching a high altitude, especially without proper acclimatization. It is a true medical emergency; if you feel its signs, then descend immediately because continuing to climb can be fatal, even for experienced hikers. 

Things to Do Before Trekking to Prevent Altitude Sickness

Before going on your trek, it’s essential to understand the right prevention methods to stay safe and healthy. Proper preparation can make all the difference, so knowing the best tips to prevent altitude sickness before trekking will help you to enjoy your journey without any health issues. This part covers important things to do before your trek to minimize the risk of altitude sickness.

Plan for a gradual ascent

 When planning your trek, choosing an itinerary that allows for a gradual ascent is one of the main preventive methods against altitude sickness. Which means include acclimatization days at intermediate altitudes, normally between 2,500 to 3,000 m before reaching higher elevations above 4000 m. These remaining days will give your body time to adjust to lower oxygen levels, reducing the symptoms like headaches, nausea, and fatigue. A slow and steady climb not only protects your health but also improves your energy levels and trekking experience. 

Get a Pre-Trek Medical Check-Up (if needed)

Before heading to high altitudes without preparation, it’s better to get a premedical check-up, which can be an important prevention method to stay safe and avoid altitude sickness. This may include tests like a Pulmonary Function Test (PFT) to check how good your lungs work, an electrocardiogram (ECG/EKG) to monitor your heart, and a chest X-ray if you have lung issues. Your doctor might also check your hemoglobin levels, test your oxygen saturation (SpO2) with a pulse oximeter, and do an exercise tolerance test to see how your body handles physical stress. Also, consult your doctor about taking acetazolamide (Diamox) or similar medicines, which can help your body adjust faster and reduce the risk of high-altitude sickness. 

Begin Physical Conditioning in Advance 

To prepare your body for the high elevation and manage altitude sickness symptoms, it’s important to start training at least 4-6 weeks before your trip. Focus on cardio exercises like running, cycling, or swimming to boost your heart and lung capacity. Also, practice hiking to build the habit of walking on uneven terrain by carrying a backpack. Adding strength workouts for your legs, core, and back will improve stamina and reduce fatigue during steep climbs. Improving your cardiovascular fitness helps your body to use oxygen correctly, which is important at higher altitudes where oxygen levels are low.

Stay well-rested before departure 

Getting enough rest before your trek is a key prevention method against altitude sickness. Make sure you’re well-rested and not lacking sleep before heading into the mountains, as fatigue can weaken your body’s ability to adjust to lower oxygen levels at high altitudes. When you’re tired, your breathing shortens, your immune system slows down, and your risk of developing altitude-related symptoms increases. Try to get 7-9 hours of good sleep each night, and avoid last-minute stress or overexertion. Starting your journey by resting well gives your body the strength and balance it needs to handle the thin air ahead.

Pack proper trekking gear 

Packing the right trekking gear plays a major role in helping you to avoid altitude sickness. Bring warm layered clothes like fleece jackets, down jackets, windproof outer shells, insulated gloves, woolen hats, neck gaiters, wool socks, base layers, waterproof pants, hats, UV–protection sunglasses, sunscreen and a warm beanie to protect against cold temperatures, which can drop at high elevations, especially above 3,000 meters. Cold stress can weaken your immune system and make it harder for your body to adjust to lower oxygen levels, increasing the risk of AMS. When your body is protected from the harsh weather, it can focus on adapting to the altitude, so pack smart and stay one step ahead of sickness.

Choosing the right season 

Choosing the correct season for your trek is one of the most important preventive steps you can take to avoid symptoms of altitude sickness. Spring (March to May) and Autumn (September to November) are considered the best times for high-altitude trekking in regions of Nepal, offering clear views, stable weather, and moderate temperatures. During these seasons, daytime temperatures range between 10°C to 20°C (50°F to 68°F) at mid-altitudes, while nights can drop to around -5°C to 5°C (23°F to 41°F). Trekking in such conditions helps to reduce the risk of cold-related stress on your body, which can otherwise make it harder to adapt to altitude. 

Pre-Trek Checklist

Medical:

• Visit your doctor to discuss altitude medications like Diamox (125–250mg twice daily).
• Start taking it 1–2 days before ascending above 2,500m if recommended.
• Get a basic health check-up to make sure you’re fit for high-altitude trekking (especially heart, lungs, and blood pressure).

Gear

• Pack warm layers, a hat and gloves, and a good windproof jacket.
• Bring UV-protective sunglasses, a 2L refillable water bottle, and a basic first-aid kit (include paracetamol, anti-diarrhea meds, band-aids, and oral rehydration salts).
• Don’t forget a headlamp with extra batteries, as power may not be available in remote areas.

 Training:

• Do 4–6 weeks of cardio training before your trek.
• Include activities like hiking with a backpack, stair climbing, or running, 3–4 times a week.
• Practice walking with your loaded daypack to get used to the weight you’ll carry during the trek.

Insurance:

• Make sure you have travel insurance that covers trekking above 2,500m and emergency helicopter evacuation.
• Double-check that the policy includes high-altitude medical care.
• Carry a printed and digital copy of your insurance policy and emergency contact numbers at all times.

Methods to Prevent Altitude Sickness During Trekking

Preventing altitude sickness doesn’t stop once your trek is started; it’s just as important to take the right steps while you’re on the trail. From how you walk to how hydrated you are, everything matters at high elevations. This section covers simple, effective methods to prevent high-altitude sickness during trekking so you can stay healthy and enjoy the journey.

Ascend slowly 

Ascending slowly is one of the most effective ways to avoid altitude sickness while hiking to higher areas. Once you’re above 3,000 meters, it’s important to manage your altitude gain to 300-500 meters per day, and schedule acclimatization days every 2-3 days or after a hard elevation climb. This slow and steady pace gives your body time to adjust to the environment, reducing the risk of AMS, HAPE, or HACE. Most cases of altitude sickness happen when trekkers ascend too fast without giving their bodies time to adapt, so walking slowly and taking regular breaks helps prevent it. Remember, the aim is not reaching the top fast; it’s to reach it healthy and safe.

Climb High, Sleep low 

The golden rule, “climb high, sleep low,” is a proven method to help your body adapt safely to high altitudes. It means trek to a higher elevation during the day, then descend to sleep at a lower altitude, like ascending to 3,500 meters during the day and sleeping at 3,000 meters. This method trains your body to handle lower oxygen levels without overloading it, and reduces the risk of altitude sickness.. Even a short descent of 300-500 meters can make a big difference in how well your body acclimatizes. So instead of heading to your next overnight stop in a hurry, consider this smart strategy: climb high, rest low, and trek strong.

Stay well hydrated 

Staying well hydrated is a simple but important way to prevent altitude sickness while hiking. At higher altitudes, your body loses water faster through breathing, sweating, and dry mountain air, even if you don’t feel thirsty. That’s why it is essential to drink at least 3 to 4 litres of water daily. Dehydration thickens your blood, making it harder to carry oxygen, which can increase the risk of headaches, fatigue, and altitude sickness. Adding a bit of salt or electrolytes to your water can also help to maintain the balance of fluid and energy levels. Remember, clear urine is a good sign you’re drinking enough, so keep that bottle closer to you and drink it often. One of the legendary mountaineers, Reinhold Messner (the first person to climb Mount Everest without the supplement of oxygen, said that “The key is going slowly and respecting the mountain. Altitude sickness is the body’s way of saying you’re going too fast. Acclimatize properly, stay hydrated, and never ignore the first symptoms—those are the golden rules.”

Eat light but frequently

Eating light but frequently is a smart and effective way to help your body deal with high altitude. At upper elevation, your digestive system slows down due to a reduction in oxygen, so eating heavy meals can make you feel bloated, tired, or dizzy. Instead, look for small, regular meals packed with energy-rich foods like rice, pasta, nuts, dried fruits, energy bars, whole grains, and soups. These are easy to digest and provide continuous energy for your body to trek throughout the day. According to nutrient experts, complex carbs are especially helpful because they require less oxygen to metabolize. Skipping meals or overeating can increase the possibility of illness, leading to altitude sickness, so keep on eating smartly and staying energized.

Avoid Alcohol and Smoking

Avoiding alcohol and smoking during your trek is one of the most important ways to protect yourself from altitude sickness while trekking in Nepal. Both substances reduce the ability of the body to absorb oxygen, which is already less at high elevations. Alcohol acts as a diuretic, causing dehydration, while also slightly stopping breathing during sleep, which can lead to lower oxygen levels at night, a dangerous moment in the mountains. Smoking damages the lungs, which makes it harder to breathe in the thin air and increases the possibility of AMS. So, for a safe and enjoyable trek, skip the booze and cigarettes until you’re back at lower altitudes.

Keep warm and Dry

Keeping your body dry and warm might sound simple, but it’s an essential part of curing altitude sickness during your trek. At high altitudes, the cold atmosphere weakens your immune system and makes it harder for your body to adjust to lower oxygen levels. Wet clothes, freezing winds, and sudden weather changes can lead to hypothermia or fatigue, which can be a big problem. Therefore, it is essential to wear moisture-wicking base layers, insulating mid-layers, and waterproof outerwear, and always pack extra pairs of socks and gloves for a better journey.

Communicate with your guide or group 

Communicating with your guide isn’t just helpful, it can be lifesaving when it comes to preventing altitude sickness. If you feel unwell, dizzy, unusually tired, or have a headache that doesn’t go away, always speak up to the guides. Guides are trained to identify the signs of AMS, HAPE, and HACE, and taking early steps like slowing down, resting, or descending can stop symptoms from being serious. Early detection and response are key to preventing altitude illness, generally at elevations above 3,000 m. Never ignore your symptoms; your guide is there to help, and speaking early can make the difference between a smooth trek and a medical emergency.

Treatment Options if Affected by Altitude Sickness

Here are some of the prevention tips to follow if you ever get caught by altitude sickness:

• Stop ascending immediately: Don’t go any higher, descend to a lower altitude because altitude sickness increases as you ascend higher. Continuing to climb is prone to altitude sickness and can make symptoms even worse, leading to more serious conditions like HAPE or HACE. Headache, nausea, or fatigue are common in altitude sickness. If they get worse or don’t improve after rest, return to a lower altitude by at least 500-1,000 meters immediately
• Rest and monitor your symptoms: Take a break at the same altitude, take paracetamol, and see if symptoms improve within 24-48 hours. Mild AMS often gets better with rest and hydration.
• Take prescribed medications (if available): Use acetazolamide (Diamox) to support acclimatization, use them under doctor prescription because it can show side effects like tingling in fingers/toes, increased urination, and taste changes. Or ibuprofen/paracetamol for headache relief. Also, carry anti-diarrhea tablets and other required medications to use them in an emergency. One of the famous personalities, Luanne Freer – Altitude Illness Expert, Everest ER Base Camp, said that “Even the fittest trekkers get AMS. The best prevention? Climb high, sleep low, and take it slow. And yes, Diamox works if used correctly under medical guidance.”
• Use supplemental oxygen if available: Oxygen can quickly relieve symptoms and is especially useful in remote areas where descent may be delayed or prolonged. Always carry a small oxygen can, or the guides for emergency situations often carry them.
• Evacuate if symptoms worsen or HAPE/ HACE is suspected: If you ever feel like your breath is not catching up, or can’t walk straight, or don’t remember where you are, then this is a medical emergency. Immediate descent of at least 500-1,000 meters, use supplemental oxygen if available, contact guides for evacuation, and he can manage for fast evacuation. 
• Use a Gamow Bag (Portable Altitude Chamber): In severe cases of altitude sickness, when descent is not possible, some trekking agencies carry a Gamow bag, a portable hyperbaric chamber. It works by simulating a lower altitude environment. Once the person is placed inside and the bag is inflated, it simulates a descent of about 1,500 meters by increasing air pressure, creating an oxygen-rich environment. Typical use involves 1–2 hour sessions, helping to stabilize the trekker until evacuation. 
• Helicopter Evacuation: In case of serious altitude sickness or emergencies, helicopter rescue is the quickest option. Reputed companies like Air Dynasty, Simrik Air, and Altitude Air operate in popular trekking regions. Costs typically range from $5,000 to $10,000 without insurance. (You can check with providers to confirm current rates.) Always ensure your travel insurance covers high-altitude evacuation.
• Emergency Contacts: Always keep a list of emergency contacts. In Kathmandu, you can dial 100 for the police or 102 for ambulance services. However, in remote trekking regions, mobile networks are unreliable, so it’s best to rely on your guide’s satellite phone or VHF radio for emergency communication. Make sure your trekking agency provides 24/7 support contacts in case of evacuation or medical help.

Treatment Steps for Altitude Sickness

Important Note on Medical Support and Insurance:

If you experience severe altitude sickness and require evacuation, you’ll likely be flown to either Pokhara or Kathmandu, where medical facilities are available. In Kathmandu, hospitals include CIWEC Travel Medicine Center, Norvic International Hospital, and Grande International Hospital, all of which are experienced in treating altitude-related illnesses. In Pokhara, reliable options include Metrocity Hospital, Manipal Teaching Hospital, and Fewa City Hospital. To ensure access to these services, it’s essential to have travel insurance that specifically covers:

• Trekking above 2,500 meters 
• Emergency helicopter evacuation
• Medical treatment and hospitalization in Nepal

Without proper insurance, rescue and treatment costs can be extremely high, especially in remote mountain areas. Always double-check your coverage before starting the trek.

What will happen to your body when you’re at high altitudes?

When you reach high altitudes, typically above 2,500 meters (8,200 feet), your body is exposed to lower oxygen levels and lower air pressure. The oxygen in the air becomes thinner, which means that in each breath, you’ll get less oxygen than you used to get at sea level. To adjust, your body begins to work harder, your breathing rate increases, your heart beats faster, and your body produces more red blood cells to carry oxygen. These are the normal changes that help you to survive and work in high-altitude conditions, a process known as acclimatization. However, this adaptation takes time, which is why slow ascent is very important.

In the early stages, you may notice shortness of breath during the activity, an increase in fatigue, or trouble while sleeping. These are common symptoms that are seen in every trekker. But if your body doesn’t adjust properly, then more serious symptoms like headaches, nausea, or dizziness can develop, known as Acute Mountain Sickness (AMS). In rare cases, if you ignore these symptoms too, then it can progress to HAPE or HACE. Both of these dangerous forms of altitude sickness are life-threatening conditions caused by the development of fluid in the lungs or brain. That’s why it is necessary to understand how your body responds at altitude and how to care for it.

Tips for Sleeping Better at High Altitudes

Getting good sleep in the mountains isn’t always easy, but it’s one of the most important things for your body to adjust to higher altitudes. Poor sleep can weaken the ability of your body to acclimate, making you more likely to experience altitude sickness. In this part of the article, you’ll find simple tricks to sleep better in the mountains so your body can rest, recover, and stay strong throughout the trek.

• Avoid caffeine and alcohol in the late afternoon and evening, as both of them disturb sleep and may cause a high risk of dehydration
• Practice deep breathing or meditation before bed to relax your body and manage altitude-related anxiety.
• Stay off screens like phones or headlamps at least 30 minutes before going to sleep, as blue lights disrupt melatonin production.
• Make a routine for bedtime and stick to it while trekking, to help you adjust your sleep cycle.
• Use earplugs and a sleeping mask to block noise and light, especially in group lodges or tents.
• Elevate your head slightly with a folded jacket or pillow so that it will be easy to breathe in thinner air.
• Eat a light, warm meal before bed because digestion helps to generate heat in the body and stabilize energy overnight.
• Stay slightly hydrated, but don’t overdrink before bed to avoid going to the bathroom in the cold at night.
• If you snore or struggle to breathe while lying flat, try sleeping on your side to improve airflow.
• If sleep issues last more than two nights or affect your ability to trek, then consult your guide or seek medical help.

Altitude Advice for Major Treks in Nepal

• Everest Base Camp Trek

The Everest Base Camp Trek goes from Lukla (2,860m) to Everest Base Camp (5,364m), passing places like Namche Bazaar (3,440m), Tengboche (3,860m), and Dingboche (4,410m). Since it reaches high altitude quickly, there’s a higher risk of altitude sickness. Most trekkers take a rest day at Namche Bazaar, and do a short hike up to 4,000m before sleeping at a lower altitude to help the body adjust. It’s very important to walk slowly, drink plenty of water, and not skip rest days so your body can get time to adapt to the thin air.

• Annapurna Base Camp trek

This trek climbs from Nayapul (1,070m) to Annapurna Base Camp (4,130m), going through villages like Ghorepani (2,874m) and Chhomrong (2,170m). It doesn’t include official acclimatization days, but many trekkers choose to rest in Ghorepani or Chhomrong. Even though the risk of altitude sickness is lower than in the Everest region, it’s still important to stay hydrated, eat well, and walk at a steady pace to stay safe and healthy.

• Manaslu Circuit trek

The Manaslu Circuit Trek starts at Soti Khola (710m) and goes to Larke Pass (5,160m), with key stops at Namrung (2,630m), Sama Gaun (3,530m), and Samdo (3,860m). It’s a remote trek, so helicopter evacuation is harder if something goes wrong. Trekkers usually take one rest day at Sama Gaun, and sometimes at Samdo too, to help the body adjust. Because of the high pass and the remoteness, it’s very important to go slowly, get enough rest, and not skip acclimatization stops.

• Annapurna Circuit Trek

Annapurna Circuit Trek starts at Besisahar (760m) and climbs to Thorong La Pass (5,416m), one of the highest trekking passes in the world. It passes through Chame (2,650m), Manang (3,540m), Yak Kharka (4,050m), and Thorong Phedi (4,540m). The high altitude and long walk make it important to rest at Manang for at least one day, and sometimes also at Yak Kharka or Thorong Phedi. This gives your body time to adjust before reaching the highest point. To stay safe, walk slowly, drink water often, and never skip rest days.

Sherpa’s Advice to Prevent Altitude Sickness

Sherpas of Nepal, as well as Our advice for preventing altitude sickness while trekking is to always go slow, stay hydrated, and listen to your body. Choose the best trekking route that allows for a slow ascent with proper acclimatization days, and don’t rush; your safety is more important than your schedule. Make sure to sleep well, eat light but regularly, and avoid alcohol and smoking during the trek. Stay in touch with your guide and trekking partners, especially if you feel unwell. Wear warm clothes, keep your gear dry, and rest whenever your body asks for it. And remember, if symptoms get worse, then descend immediately. A safe trek is always better than a fast one. Here’s advice from Nims Purja, too (record-breaking Nepali mountaineer who climbed 14 peaks in 6 months): “Train hard, but listen to your body up there. Hydration, nutrition, and proper acclimatization are non-negotiable. I’ve seen the toughest people humbled by altitude. Respect the elevation.”