Avoiding Altitude Sickness While On Trek


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Trekalayan DestinAsians


Travel Tips


24 Jun 2022

Around 37 to 32 BC, a high Chinese official Too-Kin documented the difficulties of crossing what was probably the Kilik Pass (4,827 meter/ 15,837 feet) and into what is now Afghanistan. He wrote about the crosses at “Great Headache Mountain” and “Little Headache Mountain” where "men's bodies become feverish, they lose colour, and are attacked with headache and vomiting." 2,000 years later, we know what Too-Kin described is Acute Mountain Sickness. 

Altitude sickness, also known as AMS (Acute Mountain Sickness), is a disorder that occurs when one cannot get enough oxygen from the air at high altitudes. It is a potentially serious medical condition that develops when you are physically active at high altitudes, where oxygen levels are low, without gradually having acclimatised to the lower air pressures.  

Tolerance to altitude and air pressures varies from person to person. Neither your fitness level nor being male or female plays a role in whether you are vulnerable to AMS. Mild altitude sickness can hit people at altitudes as low as 2,400 metres (8,000 feet), though “susceptible individuals” can develop symptoms as low as 2,000 meters (6,500 feet). However, serious symptoms are quite rare below 3,700 meters (12,000 feet). At about 5,500 meters (18,000 feet) each breath contains approximately half of the oxygen molecules found at sea level. AMS is not always a gradual worsening of the altitude related symptoms. It can have a rapid, severe onset and disable a trekker in minutes. 



Air is thinner at higher altitudes, resulting in the number of oxygen molecules per breath to decrease. When one climbs to higher elevations too fast or stays there for too long, the body tries to adjust to the sudden oxygen shortfalls by breathing faster, compelling the heart to beat faster too. Even though breathing faster raises blood oxygen level, they do not reach the desired concentration levels. The heart and the lungs, now, have to work harder to raise the oxygen levels in the blood. This has a major impact on the body’s physiology. The body responds to the lowering of oxygen level by altering blood acidity level, lung pressure, electrolyte levels, and fluid and salt balance.   


Acute Mountain Sickness (Drop in oxygen saturation) 

Acute Mountain Sickness or AMS is by far the most common disorder experienced by most people. The drop in oxygen molecules in every breath at high altitudes, combined with increased physical activity, will only increase oxygen demand. The reductions in the oxygen saturation in the blood leads to headaches, fatigue, nausea, loss of appetite, and insomnia or restless sleeps. It is also important to consider other possible causes like dehydration and hyponatremia. AMS usually occurs 1 to 24 hours of ascending to high altitudes and last for around 24 to 48 hours as long as one does not ascend any higher. 

High Altitude Cerebral Edema (HACE) 

At the extreme end AMS can progress to High Altitude Cerebral Edema (HACE) in which the lack of oxygen causes fluid to leak through tiny blood vessels into the brain, which leads to swelling. In addition to AMS symptoms, one may experience profound fatigue, weakness, inability to walk with a normal gait, lack of concentration, confusion, and delirium. The onset of HACE and developments of the most serious symptoms can be extremely fast. It can put excessive pressure on the brain and can result in coma or death. HACE is an emergency and warrants immediate descent to lower altitude and emergency medical care. 

High Altitude Pulmonary Edema (HAPE)  

The third variation, High Altitude Pulmonary Edema (HAPE), is distinct from the other two, in which capillaries damaged by altered pressure leak fluid into the lungs. This can lead to pneumonia-like symptoms, and can be dangerous if it occurs during sleep. In addition to AMS symptoms, one may experience severe coughing, shortness of breath that is out of proportion to exertion level, and a fullness sensation in the chest. Even so, High Altitude Pulmonary Edema can occur without any other symptoms of AMS. HAPE is an urgent medical problem requiring immediate descent to lower altitude and emergency medical care. 

AMS is very common and generally dissipates after a couple of days if one takes necessary precautions. HACE and HAPE are potential killers that require urgent treatment and generally signals the end of your trip. 



Like protagonists from action/thriller movies who meditate underwater to train their body to perform for a sequence that suspensefully leaves them deprived of oxygen, the best effective way to acclimatise to the high altitudes is by gradually allowing our body to adjust to the lowering oxygen level. Thankfully, we will not have to take up similar extreme forms of trainings to combat altitude illness.  

The most important and effective way is by ascending slowly to higher altitudes, gradually over several days to allow the body to acclimatise and adjust to the decreasing level of oxygen. It would also help if we gradually increase our physical exertion level at altitudes for the first few days. Lastly, we should stay well-hydrated (at least three litres of water every day while on trek) and avoid consuming alcohol for the first few days at altitude.  

If at any time you may be experiencing headache and one of the symptoms of AMS, it is not necessary to worry about. Please report your experiences to your guide for assessment, stay relaxed, drink lots of fluid (of course, not alcohol) and rest. As your body gets used to the altitude, the symptoms should go away. 

Our guides are highly experienced in working at altitudes and always keeps a look out after our trekkers. They monitor all of our trekkers closely, staying alert against any signs of deteriorating disorders, which includes checking your pulse and blood oxygen saturation level, and evaluating your acclimatisation status. It is vital that you share information about your health and any symptoms you may be experiencing fully and openly. Failing to do so can put yourself, and your fellow trekkers as well, at risk.  


For an accurate diagnosis, one needs to reach at least 2,400 meter/ 8,000 feet experience a headache. Because headache can also be a symptom for dehydration, it is important to stay well hydrated during the trek. They must also demonstrate one of the following symptoms and signs.   

    • Lack of appetite, nausea, or vomiting 
    • Exhaustion or weakness 
    • Feeling lightheaded or dizziness 
    • Insomnia or restless sleep 
    • Numbness, pins and needles 
    • Shortness of breath upon exertion 
    • Feeling sleepy or drowsy 
    • General malaise 
    • Swelling of the hands, feet, and face 
    • Rapid persistent pulse 

    Common symptoms to High Altitude Cerebral Edema (HACE) 

    Signs of swelling of the brain include: 

      • A persistent headache that does not respond to painkillers 
      • Unsteady gait or clumsiness, difficulty speaking or walking 
      • Increased vomiting and nausea 
      • Numbness 
      • Dizziness 
      • Disorientation or confusion, gradual loss of consciousness 
      • Hallucination or vision problems 

      Common symptoms to High Altitude Pulmonary Edema (HAPE) 

      Fluid in the lungs can cause the following: 

        • A persistent dry cough, often with pinkish sputum 
        • Excessive sweating or fever 
        • Shortness of breath, panting even while resting 
        • Tight or congested feeling in the chest 
        • Gurgling or crackling sound whilst breathing 
        • High pulse at rest (90 to 100 bpm) 
        • Blue or grey lips and/or fingernails 

      Go to a lower altitude, as fast as you can, if your symptoms are moderate to severe, they get worse, or medicine or treatment does not help. Go down at least 1500 ft (450 m) and rest until symptoms have completely subsided. A member of our trek team will always accompany you as you descend to lower altitude and make sure you receive all emergency and medical assistance.  

      It is important to recognize the symptoms, as there are limited medical services available in the remote Himalayan regions.  


      Many of the most popular trekking routes in the mountainous areas, in Nepal, are remote and inaccessible, with scarce health facilities and medical clinics. Where available, we will consult the medical team for assessments and advises, but where a health clinician cannot be reached, your guides will have to assess your health.  

      If your guides have concerns about your health, or believe that continuing the trek would be at risk for you, they will insist that you begin your descent immediately. A decision, as such, can be a difficult choice, with regard to who gets to call if the symptoms will continue to worsen or slowly subside. We will follow the below guidelines to make sure that you remain safe and successfully complete your trek. 

      Your blood oxygen level will be measured. Sources suggest the normal level should be above 80%. If it falls below 75% and do not recover, you must immediately begin your descent. If it does not rise above 75%, you will be monitored closely while continuing your trek.  

      Your Lake Louise Acute Mountain Sickness score will be measured. Though the Lake Louise AMS score is intended for study purposes only, it is the best tool we have to assess the severeness of AMS. If your score is above 8 you must descend. If it is between 6 and 8, your guides will consider your blood oxygen levels, and your overall well-being to determine whether it is safe for you to continue. Again, it is of utmost important that you notify your guides immediately if you begin to feel discomfort and disorders. 

      On an important note, you are required to have at least a private medical and evacuation insurance to participate in tourist activities in Nepal. Should you require medical assistance and repatriation, your insurance policy should cover the cost for you. Find out more about insurance coverage for travelling in Nepal, here.  


      Bistarai, Bistarai” (Slowly, Slowly) 

      Bistarai, bistarai” is a phrase you will hear quite a few times during your trek, as much as the universal, all-in-all, Nepali greeting “Namaste”. Your guide in his calm, soothing, low voice will occasionally suggest you to walk slowly or take it easy. It is best to maintain a low breathing rate as we ascend, and slow down if you find yourself breathing hard. Overworking your heart and lungs puts you at much higher risk of AMS. 

      “Climb High, Sleep Low” 

      For adventurers in high altitudes, following the simple maxim “climb high, sleep low” is a well-known strategy and widely used practice. The idea is to expose the body gradually to higher altitudes, forcing it to adjust, and then return back down to recuperate at an altitude the body is already used to.  

      We will make efforts to allow you to take short walks at higher altitudes every day, and descend down again to sleep at lower elevations. 

      Staying Hydrated  

      As advised above, you need to drink at least three litres of water every day during your trek. Staying hydrated in regular intervals helps to maintain levels of oxygen in your body at high altitudes where the air is thinner. In the cold climates of the mountain, you may not realise your sweating from physical activities, or losing water even while breathing as clouds exhale through your mouth. Proper hydration not only makes AMS less likely, it makes you less vulnerable to host of other problems such as dehydration and indigestions. So, drink as much as you can, more than you feel you need to. 


      Over-the-counter medicines, such as Acetaminophens (Tylenol), Ibuprofen (Advil, Motrin) can be taken for headaches. Anti-inflammatory medicine can also help to reduce feeling sick to your stomach or other mild symptoms. 


      Many studies have been conducted on the effectiveness of acetazolamide (Diamox) in preventing AMS. Diamox speeds up how fast your body gets used to the altitude, as a result has become the first-choice preventive drug. It is important to remember that Diamox is only a preventive medicine, not a cure for AMS. Start taking it a day before you begin ascending and continuing until two days after you reach your highest altitude. Various sources recommend the typical adult dose as 125 mg every 12 hours. As with any drug, you should seek professional advice before considering it. 

      This medication may cause some side effects, including pins and needles in the face, fingers, and toes, as well as excessive urination, and, in rare cases, blurred vision. 

      What if you have a lung problem or other medical conditions? 

      Experts do not know much about how altitude affects other diseases and medical problems. It is best advised to talk with your doctor about altitude sickness and other medical concerns regarding the trip.  

      At the end, the most important point to take away from this, is that there are no guarantees. You can follow all the advice, ascend gradually, medicate yourself perfectly, spend nights acclimatising – and still end up with a crushing headache one morning. People respond and adjust to altitude every differently. But as far as science and medical studies are concerned, these are the best ways to minimize the risk of altitude sickness. Either way, our experienced guides and trek teams will do their best to make sure you receive all the assistance and complete your trek safely.   



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