Trekking in Nepal takes you through beautiful mountain villages, deep valleys and some of the highest mountain passes in the world. As you climb higher into the Himalayas, the air pressure decreases, making less oxygen available to your body. If you ascend too quickly, you may develop altitude sickness.
Altitude sickness can affect anyone, including experienced trekkers and physically fit travellers. It is particularly important to understand the risks when trekking above 2,500 metres, whether you are visiting Everest Base Camp, crossing the Larkya La Pass on the Manaslu Circuit or exploring other high-altitude destinations in Nepal.
At Beyond the Limits Treks & Expedition, the safety of our guests comes before completing any itinerary. Our experienced local guides and trek leaders understand the importance of acclimatization and are trained in first aid. We encourage every guest to recognize the symptoms of altitude sickness and communicate openly with their guide throughout the journey.
This guide explains the three main types of altitude illness, their warning signs, ways to reduce your risk and what to do if symptoms develop.
What is altitude sickness?
Altitude sickness occurs when your body has difficulty adjusting to the reduced oxygen available at higher elevations. It is more likely when you gain altitude faster than your body can acclimatize.
There are three main types of altitude illness:
- Acute Mountain Sickness (AMS): the most common form, usually causing headache, nausea, dizziness and tiredness.
- High Altitude Pulmonary Edema (HAPE): a serious condition in which fluid builds up in the lungs.
- High Altitude Cerebral Edema (HACE): a life-threatening condition involving swelling of the brain.
AMS is usually mild at first but can become severe. HAPE and HACE are medical emergencies requiring immediate attention.
1. Acute Mountain Sickness (AMS)
AMS is the most common altitude-related illness among trekkers. Symptoms often develop within several hours of reaching a higher elevation, particularly during the first night.
Common symptoms of AMS
- Headache, often the first warning sign
- Nausea or vomiting
- Dizziness or light-headedness
- Loss of appetite
- Unusual tiredness or weakness
Difficulty sleeping is also common at altitude, but it does not necessarily mean you have AMS.
What should you do if you experience AMS?
Tell your guide immediately and stop ascending. Mild AMS often improves with rest and time to acclimatize at your current altitude. You should not sleep at a higher elevation until your symptoms have completely disappeared.
If your condition worsens despite rest or treatment, descend to a lower altitude and seek medical assistance. Never continue ascending simply to keep up with your planned itinerary.
2. High Altitude Pulmonary Edema (HAPE)
HAPE occurs when fluid collects in the lungs, making it difficult for the body to absorb oxygen. It can develop rapidly and may occur even without the usual symptoms of AMS.
Warning signs of HAPE
- Unusual breathlessness while walking
- Difficulty breathing even when resting
- A persistent cough, sometimes producing pink, frothy or blood-tinged mucus
- Tightness or congestion in the chest
- Severe weakness or difficulty walking
- Blue or grey lips or fingernails in advanced cases
What should you do if HAPE is suspected?
Stop ascending and inform your guide immediately. Arrange an urgent assisted descent and emergency medical attention. Supplemental oxygen should be provided if available. Keep the affected person's physical activity to a minimum and do not leave them alone.
Oxygen or medication must not delay descent or medical evacuation.
3. High Altitude Cerebral Edema (HACE)
HACE is a severe altitude illness that causes swelling of the brain. It can develop from worsening AMS and may progress quickly.
Warning signs of HACE
- Severe headache, often with worsening AMS symptoms
- Confusion, disorientation or unusual behaviour
- Difficulty walking straight or maintaining balance
- Loss of coordination
- Extreme drowsiness or difficulty staying awake
- Loss of consciousness in advanced cases
What should you do if HACE is suspected?
Arrange immediate assisted descent and emergency medical care. Give supplemental oxygen and appropriate emergency treatment under trained supervision when available. A person with suspected HACE should never descend alone.
4. How to prevent altitude sickness while trekking in Nepal
There is no guaranteed way to prevent altitude sickness, but careful planning and gradual acclimatization can significantly reduce your risk.
Ascend slowly. Once above 3,000 metres, aim to increase your sleeping altitude by no more than 500 metres per day, with an acclimatization day every three to four days where possible.
Drink enough water. Stay hydrated according to your thirst and physical activity, without forcing excessive amounts of water.
Eat regularly. Maintain your energy with nutritious meals, including carbohydrate-rich foods such as rice, potatoes, bread and noodles.
Walk at a comfortable pace. Take regular breaks and avoid unnecessary physical exertion, particularly during the first days of your ascent.
Avoid alcohol and sedatives. Alcohol and certain sleeping medications may interfere with breathing and make it harder to recognize altitude-related symptoms.
Speak to your doctor before trekking. Acetazolamide, commonly known as Diamox, may help prevent altitude sickness in some travellers. Your doctor can advise whether it is suitable for you, especially if you take regular medication or have an existing medical condition.
5. When should you descend?
| Mild AMS | Rest at your current altitude. Do not ascend until your symptoms have completely resolved. |
| Worsening AMS | Descend with assistance and seek medical attention, particularly if symptoms become severe or fail to improve. |
|
HAPE or HACE |
Arrange urgent assisted descent, emergency treatment and medical evacuation as needed. Do not wait for the symptoms to improve on their own. |
If severe weather or another emergency makes immediate descent impossible, seek urgent medical guidance and use available emergency oxygen or other appropriate treatments while arranging evacuation.
Your safety with Beyond the Limits Treks & Expedition
Our approach to high-altitude trekking begins with careful itinerary planning, appropriate acclimatization and experienced local guides. We understand that every guest adjusts to altitude differently, so the pace of a trek sometimes needs to change.
Our guides encourage guests to report symptoms early and help arrange medical assistance when necessary. If your health requires an additional rest day, a change of route or an immediate descent, your safety will take priority over the original itinerary.
We also strongly recommend that all high-altitude trekkers purchase travel insurance covering their planned maximum altitude, emergency medical treatment and helicopter evacuation. Medical facilities are limited in some remote Himalayan regions, and rescue arrangements can depend on weather and local conditions.
Our goal is to help you experience Nepal's mountains safely, enjoy your journey and return home with wonderful memories.
In remote treks like Kanchenjunga and Manaslu where mobile network doesnt work properly we send satelliate phones, so you can contact Kathmandu head office in case of emergency.
Frequently Asked Questions
Can physically fit trekkers get altitude sickness?
Yes. Fitness, age and previous trekking experience do not guarantee protection against altitude sickness. Even experienced mountaineers can become ill if they ascend too quickly.
At what altitude does altitude sickness begin?
Altitude sickness can develop above approximately 2,500 metres, although individual susceptibility varies. The risk generally increases with faster ascent and higher sleeping elevations.
How long does mild altitude sickness last?
Mild AMS often improves within one or two days when you stop ascending and allow your body to acclimatize. If symptoms persist or worsen, descend and seek medical advice.
Can I continue trekking if I have a headache?
A headache at altitude may be an early sign of AMS, particularly when accompanied by nausea, dizziness or fatigue. Inform your guide and avoid ascending further until you have recovered.
Does Diamox prevent all types of altitude sickness?
No. Acetazolamide can help prevent AMS and improve acclimatization in suitable travellers, but it does not guarantee protection. Proper acclimatization and recognizing warning signs remain essential.
Is helicopter rescue always available in Nepal?
No. Helicopter evacuation depends on weather, visibility, and operational conditions. Trekkers should have appropriate insurance and understand that emergency assistance may be delayed in remote areas. If you are in higher location, our local team will descend you to a health post if an emergency helicopter is not possible. Please knoe that your safety is top priorty and the company will do everything it can to save lives in case of an emergency, but another lives must not be lost while saving one lives.