What is Acute Mountain Sickness?

  • Last Updated on Apr 2, 2024

Acute mountain sickness (AMS) or High Altitude Sickness is a condition that can arise at altitudes higher than 8,000 feet above sea level. Everyone can get AMS because of the atmospheric pressure and oxygen concentration levels get lower. The beginning symptoms of altitude sickness are headache, nausea, dizziness, fatigue, and difficulty sleeping at a new altitude. In rather severe cases, it may result in what seems to be potentially fatal circumstances like HACE (High Altitude Cerebral Edema) and HAPE (High Altitude Pulmonary Edema). We need emergency medical treatment and evacuation in HAPE and HACE cases. Altitude sickness manifests itself as a result of the body's inability to adapt to the reduced oxygen environment at high altitudes. Hence, following a well-planned acclimatization regime of ascent very slowly, clear hydration, having no alcohol or strenuous activity, and medication like acetazolamide, if essential, is a significant issue here. Awareness, precaution, and accurate tracking of symptoms are fundamental for any traveller attempting to celebrate the time they spend at high altitudes. It will ensure their safety and make their experience enjoyable.

Table of Contents

All About Acute Mountain Sickness

We all know how dangerous is High Altitude Sickness. It is said that getting AMS (Acute Mountain Sickness) is fine but dying with AMS is not good. Everyone has a chance to get AMS while doing high-altitude trekking in Nepal. So we strongly recommend all travellers get some information on What is Altitude Sickness and What to do after getting it. While doing a trek like Everest Base Camp Trek, Everest Three Passes Trek, Manaslu Circuit Trek, Everest Renjo Pass Trek, Gokyo Lake Trek, Annapurna Circuit Trek, etc has more chances to get AMS. So, everyone who is going on high-altitude treks is at risk of getting AMS because

You leave the comforts of your daily living.

Different climatic conditions. 

The level of oxygen in the atmosphere is low

Your previous medical history might act as a predisposing factor.

Acute Mountain Sickness (AMS) or High Altitude Sickness

  • It is a syndrome complex of (a) headache (b) nausea (c) dizziness (d) sleeplessness and (d) fatigue. Of course, headache is a cardinal symptom.
  • Nobody is immune to AMS above 2000 – 2500m.
  • It is not related to physical fitness or gender.
  • Early AMS feels exactly like an alcohol hangover. It is also heralded by the feelings of deep inner chill or a sense of not being well.
  • Late or advanced AMS denotes the increase in severity of the above-mentioned symptoms.
  • A typical picture will be: a porter arrives at a high altitude carrying a heavy load. Immediately, he goes into a corner of the darkroom and rests there covered with a blanket from head to toe. He doesn’t want any tea or snacks. He starts to throw up once in a while. When asked he says he has the worst headache as if somebody is hammering a nail into his forehead and he feels terrible. He is still huddled in the corner at dinner time. When friends bring him food, he does not even want to look at it. When asked, he says I want to go down.
  • If not infected, AMS could process two fatal complications: (a) High Altitude Cerebral Edema (HACE), meaning swelling of the brain or water in the brain. (b) High Altitude Pulmonary Edema (HAPE), meaning water in the lungs.


It is characterized by increasing headache and vomiting, staggering gait, altered consciousness, and other neurological signs. It is thought to be the progression of AMS. The condition develops more rapidly in the night in someone with AMS, probably because of a further decrease in ventilation during the night. This explains the common belief in our people that somebody with a bad headache should not go to sleep. This is true but what is equally important is that they should not remain in the same place either. This fact highlights the importance of keeping a high index of suspicion and making decisions about descent in the day and not waiting for the night or the next morning. The single most important test to detect HACE in somebody with AMS is the tandem gait test where a person walks straight on a line in a hill-to-toe fashion. If he falls beyond the line, it is strongly suggestive of HACE. The person becomes comatose soon thereafter. 
It is indivisibly fatal unless interfered with.


It is characterized by increasing breathlessness even at rest, productive cough, and bluish discolouration of lips and tongue. The sputum may become blood-tinged later on. It usually strikes the second night onwards. The bluish discolouration is a late sign and should not happen in the hands of good friends. One important thing about HAPE is that it can occur in a setting outside of AMS. People can have full-blown HAPE without headaches and other symptoms of AMS. Thus when conformed with the above signs and symptoms of HAPE, those should not be ignored or dismissed in the light of the absence of headache. HAPE likewise seems to be a completely different pathology
It is invariably fatal unless interfered with.

Why does it (AMS) happen?

It happens because of low atmospheric pressure.
A low atmosphere leads to low oxygen tension in the air which we inhale and causes a series of changes in the body which may lead to AMS. There is a liking of flute from the bloodstream into the brain. The arteries of the lunges also constrict causing an increase in pressure in them which promotes fluid leakage into the lunges. These occur when our body does not get sufficient time to adapt to the change in pressure. Some people may be unable to adapt at all because of some abnormalities in their bodies e.g. absence of one pulmonary, the relative proportion of their brain and the skull, etc.

What are the risk factors for AMS?

  • Rapid ascend is the main risk factor.
  • Dehydration, airway infections, overexertion, sleeping pills, obesity, and alcohol are other risk factors.
  • The previous history of altitude sickness is the best predictor of whether one would be stuck again.
  • Non-flexible itineraries, peer pressure, and tough and stoic personality are some other risk factors.
  • Excess chill and cold exposure is a known risk factor for HAPE.

What do we do to prevent AMS?

  • AMS is preventable and treatable.
  • Our body is a Machine. It always gives signs when it is malfunctioning. All we need to do is to listen to our body and help not hinder its process.
  • By slow ascending, we can digest the altitude, the process is called acclimatization. Here, our body gets sufficient time to adjust to the high altitude. It is prudent to take a rest day every third day with the rate of ascending not more than 400m per day after the altitude of 3000m. Climbing high and sleeping low is another of the dictums of altitude medicine. Moderate exertion on rest days is also recommended.
  • People acclimatizing well will have increased dieresis which helps prevent fluid from accumulating in the body.
  • The process of acclimatizing can be accelerated by the use of a drug called acetazolamide (diamond) taken at a dose of 250mg twice daily (5 mg/kg for kids).

How do I know where I have AMS ??

All ailments in the heights are altitude sickness unless proved otherwise. The tendency to rationalize and altitude the initial symptoms of altitude sickness to something else must be avoided and discouraged.
There is a ‘self-assessment and scoring system ‘to help you know when you are with altitude sickness. It is called the Lake Louise scoring system. All should use this to score themselves once in the morning and once in the late afternoon. In this out of a total of 15 points, a score of 3 or more with headache plus any other symptoms denotes AMS. The severity is classified as:

3 to 6: mild AMS
7 to 9: moderate AMS
10 or more than 10: severe AMS
                          Read the Everest Base Camp Trek or the  Annapurna Base Camp Trek

What is the treatment of AMS?

  • The million-dollar saying is ‘go down, go down, and go down’.
  • There is no magic altitude at which you should descend. Go down to the place where you were comfortable before. This is usually about 300m (1000f) or more.
  • Stay where you are and do not ascend if you have moderate AMS.
  • If one is badly stuck, we could only “buy time for him/her to go down by the use of (a) injectable or oral steroid (dexamethasone at the dose of 4 to 8 mg 6 hourly), (b)oxygen, (c) Diamox, (d) pressure bag (Gamow bag and (e) diuretics (a drug which makes one pee)
  • Nifedipine, a drug used commonly in hypertension could be used in a setting of HAPE at the dose of 10 mg three to four times per day.
  • Diamox should be avoided in people who are allergic to sulfa drugs. The most common side effects are the tingling of the hands and feet and the easy and the lips. Some might experience that the aerated drink tastes flat. People may wake up several time times in the night because of the diuretic effect.
  • Gastritis is the most common side effect of dexamethasone and can be effectively talked about with the use of drugs like ranitidine.
  • Breathing Oxygen reduces the effects of altitude illness.
  • -Ibuprofen is also effective at relieving altitude headaches.

Remember, all there is only buy time. One still needs to go down, go down, and go down.

The following might help you to stay away from AMS and its complications.

The things you have to do to avoid AMS

  • Listen to your body
  • Drink plenty of safe warm water. (Around 3 litres per day). Dehydration predisposes to altitude sickness.
  • Let the doctor know if you are taking any medicines.
  • Let the doctor know of your previous illness/ surgeries etc. (they might need to prepare the medications accordingly.
  • Stay warm. Take it easy. Light activity during the day is better than sleeping because respiration decreases during sleep, exacerbating the symptoms.
  • Accept your susceptibility to AMS
  • Be prepared to stay behind or return earlier than the group if you have bad altitude sickness.
  • Understand that you are in an unprivileged situation and things can be less than expected.
  • Eat a high carbohydrate diet (more than 70% of your calories from carbohydrates) while at altitude.
  • Leave a trekker behind in your group with someone who doesn’t speak the trekker language.

The things you don't have to do in high altitude

  • Attribute headache, fatigue, etc to cold weather or exertion
  • Over-exert yourself when you first get up to altitude.
  • Take sedatives.
  • Try to just push yourself. The courage displayed on inappropriate occasions is foolishness, not bravery
  • Be tempted to drink alcohol. (One can drink while coming back, that is while descending.
  • Assume that you would be stuck the last.
  • Be very religious and tough. ‘Victory is not reaching g the top but coming back safe’.
  • Get frustrated.
  • Present late
  • Take classic baths. (Cold predisposes one to AMS, HAPE)

If you are looking for experienced trekking guides and porters you can mail Nepal Gateway Trekking,  we have altitude train trekking guides and porters.

Rajendra Thapa

Rajendra Thapa

"Take only memories, leave only footprints' -Chief Seattle 

Namaste! Greetings from the Himalayas!! I am Rajendra Thapa, a promising and adventurous wanderer and a travel guide from the beautiful country Nepal. Nepal is a country duct between the gorgeous mountains of the gigantic Himalayas and the lost jungles of the Terai and also a home to multicultural people with various traditions. I am passionate about traveling, trekking, hiking, and photography. You can find my travel experiences and blogs on my Instagram, Facebook, and YouTube.
I was born in a small countryside full of greenery and fresh air on the lap of Ganesh Himal far from the city chaos. Growing up, I was always interested in exploring things,  places, people, and lifestyles, which developed into my career. Through the company Nepal Gateway Trekking Pvt Ltd. I am serving to share my knowledge, experiences, and guidance regarding various Himalayas base camps, jungles, cultural monuments, historical sculptures, and many more adventurous things to make your lifetime experiences amazing, after all, travel is all about having lifetime experiences with beautiful memories.