Often starting at 3000 m, Acute Mountain Sickness (AMS), or Altitude Sickness is an important medical consideration while trekking in Nepal because most of the trekking routs Nepal are above 3000m. Symptoms occur due to low concentration of oxygen and decrease in atmospheric pressure making breathing difficult leading to low oxygen level in body. Body tries to adapt to lower amounts of oxygen in the air mainly by increasing the rate and depth of breathing so you breathe faster and deeper. There is also an increase in heart rate. Both of these mechanisms try to bring more oxygen to the body. When the climbing is too fast above 3000m, body fails to supply enough oxygen. The lack of oxygen causes fluid leakage and accumulation in between cells in the brain and/or the lungs leading to mild or severe symptoms.  Mild symptoms of acute mountain sickness or AMS are headache, loss of appetite, nausea, fatigue, lack of sleep and dizziness. These symptoms can resolve once someone is acclimatized e.g. by spending one or two extra nights at the same altitude or symptoms may worsen needing someone to descend to lower altitudes.

AMS can progress to High Altitude Cerebral Edema (HACEand symptoms of HACE are mental confusion, difficulty with balance and co-ordination. Fluid accumulation in the lungs can lead to High Altitude Pulmonary Edema (HAPE). HAPE results in shortness of breath at rest, extreme fatigue, cough – dry in the beginning, and later productive of frothy or blood-tinged sputum. HAPE and HACE are severe symptoms, often co-exist in severe cases and can be rapidly fatal if untreated.

Prevention of Altitude Sickness:

The complications of Mountain Sickness are preventable if people listen to their bodies and follow simple guidelines:

  • Pay attention to your body and be aware of the initial symptoms of AMS. Do not ascend with these symptoms. Never ascend to sleep at a new altitude with any symptoms of AMS.
  • Ascend slowly.  Increase your sleeping altitude by only 300-500m per day.  Try climbing higher during the day and coming down to sleep. (Climb high, sleep low)
  • Descend if the symptoms become severe or if you begin to experience HACE and/or HAPE.
  • Get Hydrated: Drink at least 4 liters of water per day, in addition to the usual tea and other beverages.
  • Dress properly for high altitude treks, with synthetic under shirts for removing sweat, a warm fleece jacket, and a down jacket to prevent hypothermia, which can predispose you to AMS and its complications.
  •  Do not smoke, drink alcohol or use medication such as tranquillizers and sleeping pills while you are at altitude. They could make any symptoms of altitude sickness worse.
  • Have Digestible FoodAlways have food which is easily digestible and also food high in carbohydrates so that the body doesn’t expend energy more than it can afford. You have to eat in small portions for frequent number of times. Avoid eating heavy, oily, junk foods while ascending in height. Limit your intake of fat and sodium in your diet.
  • Avoid Exercise. First of all, when you go for height you have to spend your first day at high altitudes relaxing. Also avoid even moderate exercise until you get accustomed to new heights. Limiting exertion is always better than using a bunch of different medications. Activities like running, lifting, hiking or straining in any capacity can worsen the symptoms of altitude sickness.


Rest and Descent: For mild symptoms, one can stay at the same altitude to see if symptoms will resolve and ascend when symptoms have resolved completely. If symptoms persist or worsen at this altitude, descent is required. For severe symptoms with HACE or HAPE, descent must begin immediately whenever feasible.

Painkillers: Painkillers, such as paracetamol or ibuprofen, can be used to treat mild headaches caused by altitude sickness.

Anti-emetic: If you are experiencing nausea or vomiting, a type of medication called an anti-emetic may be useful. Promethazine is an anti-emetic medicine often used by people with altitude sickness.

Acetazolamide (Diamox): Patients with AMS may benefit from treatment with a diuretic drug called acetazolamide. This drug increases the production of urine. As a result, the pH of the blood is decreased, stimulating the patient to breathe more. When patients breathe more, they have higher levels of oxygen in the blood. Therefore, acetazolamide is taken to help prevent or reduce symptoms of AMS. This drug has also been shown to improve symptoms of insomnia in AMS patients. This is generally useful for mild-moderate AMS. Dosage: One 250 mg tablet two or three times a day.

Dexamethasone: A very potent steroid used in High Altitude Cerebral Edema temporarily to facilitate descent. This drug improves the symptoms without improving acclimatization. It is not recommended to ascend while still taking this drug by a symptomatic person. Dosage: 8mg initially, then 4 mg every 6 hours.

Nifedipine:  This is useful in HAPE by lowering pressure in the pulmonary blood vessels and thereby decreasing fluid in the lungs.

Oxygen:  Increasing your oxygen intake with bottled oxygen or portable hyperbaric chambers (also known as Gamow) can help temporarily improve some of the symptoms of altitude sickness.

Gamow or PAC Bag: This is a portable bag which, when inflated, converts into a high pressure bag in which an individual with severe symptoms of HACE or HAPE is put and air is pumped in with a foot-pump. Pressure created inside the bag increases the oxygen tension and a person can improve rapidly. This is used to tie a person over an acute crisis before descent is possible or pending helicopter evacuation.  Many groups that trek to high altitudes in remote places are nowadays taking this bag with them. These can be rented in Kathmandu or overseas.