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High Altitude Sickness

High Altitude Sickness

How to Prevent Altitude Sickness for Trekkers

1. Drink 5 Liters of Water Per Day

Quite simply, drink a minimum of five liters of water per day, no matter what. This is easier at lower elevations when it’s hot, but becomes more burdensome when temperatures cool off and you perspire less. After a few liters you may feel properly hydrated, but your body is doing extra work with less oxygen and needs the water. Force down five liters per day, without exceptions.

2. Avoid Dramatic Gains in Elevation

Treks at altitude should avoid big single-day gains in elevation (more than 1,500 vertical feet). A common misconception about trekking at high altitude is that physical condition dictates the body’s ability to fend off altitude sickness. This causes many people who are “in good shape” to ignore the rules of acclimatization, go too high too fast, and have problems. Your itinerary should factor in altitude gains and consequently some hiking days will end early. Embrace the pace, rest your legs, and hydrate.

3. Climb High, Sleep Low

Thorong La Pass (5,416 m) on the Annapurna Circuit | Credit: Ali Beittoei

You will acclimatize better if you expose yourself to higher altitudes but return to a lower altitude to sleep. After setting up camp, scramble up a nearby hill, scope out the scenery, and head back down for a better night's rest. When you have a rest day, use the opportunity to hike to higher elevations and back down—even a few hundred vertical feet is worth the effort. At higher altitudes—around 10,000 feet and above—this rule becomes even more important as your body is learning to cope with considerably less oxygen. 

4. Eat, Eat, Eat…

Your body is doing more work than usual so make sure to stay nourished and full of carbohydrates. For a dependable snack, Nepal has embraced the Snickers bar wholeheartedly and it can be found even in the tiniest villages (and for very cheap). Too much sugar, yes, but full of good things like nuts and chocolate. Do a good deed and buy some for your porters and guide whenever possible.

5. Listen to Your Body

By following the above rules, you will greatly increase your odds of staying healthy throughout your trek, but everybody reacts differently to altitude so pay close attention to how you feel. Every trek should have rest days built in and you shouldn’t be afraid to use them. Stay hydrated, wear sunscreen, and have layers available for protection from the powerful sun. Avoid alcohol and other substances. Monitor yourself and always communicate any health concerns to your group. 

An estimated 75% of people feel some affects of altitude, mostly in the form of headaches, nausea, fatigue, and trouble sleeping. These are actually mild manifestations of Acute Mountain Sickness (AMS).  Mild AMS should not interfere with normal activity and the symptoms should subside as acclimatization occurs. As long as the symptoms are mild, it’s generally okay to continue hiking up at a moderate rate. If feeling poorly persists or worsens, turn around.

Medications for Altitude Sickness

The only treatment for altitude sickness is descent, but medication can help with the symptoms. Consult a doctor before use.

  • Ibuprofen can be used to treat the symptoms of mild altitude sickness such as headaches and nausea.
  • Diamox (Acetazolamide) is a respiratory stimulant that helps the body metabolize more oxygen, especially at night, thereby accelerating the process of acclimatization. Diamox can be used as a prophylactic, particularly by those making unavoidably large ascents.

Severe Problems

In severe cases altitude sickness can be truly life-threatening. If a trekker ever gets an unusual or severe headache, or feels unusually short of breath, they should immediately descend 2,000 feet (600 meters), no matter the time of day. High Altitude Pulmonary Edema (HAPE), excess fluid in the lungs, and High Altitude Cerebral Edema (HACE), swelling of the brain, are rare but life threatening conditions that require immediate descent and medical attention.


Altitude Sickness, often known as Acute Mountain Sickness (AMS) is particularly an important consideration while trekking in Nepal. Altitude Sickness means the effect of altitude on those who ascend too rapidly to elevations 3000m. The initial symptoms of AMS are as follows:

  • Nausea, vomiting
  • Loss of appetite
  • Insomnia / sleeplessness
  • Persistent headache
  • Dizziness, light headache, confusion
  • Disorientation, drunken gait
  • Weakness, fatigue, lassitude, heavy legs
  • Slight swelling of hands and face
  • Breathlessness and breathing irregularly
  • Reduced urine output

These symptoms are to be taken very seriously. In case of appearance of any of the above symptoms any further ascend should be reconsidered; otherwise more serious problems may occur which can even cause death sometimes within a few hours. The only cure for the Altitude Sickness is to descend to a lower elevation immediately. Acclimatization by ascending to no more than 300 to 500 meters per day above 3000 meters and the proper amount of rest are the best methods for preventions of AMS.


  • Less Oxygen
  • Low pressure ie: Barometric Pressure
  • Rapid Ascent
  • Possible Dehydration
  • Hypothermia


AMS: Acute Mountain Sickness

HAPE: High Altitude Pulmonary Edema

HACE: High Altitude Cerebral Edema



  • Mild symptoms feels like a hangover / not feeling well:
  • Headache
  • Fatigue / Tiredness
  • Nausea
  • Shortness of Breath
  • Loss of Appetite
  • Disturbance in Sleep
  • Dizziness


  • Water in Lungs.
  • Increasing shortness of breath even at rest
  • Severe cough – Dry / productive
  • Very tired unusual fatigue while walking
  • High pulse rate, ie: 110
  • Blueness of face, lip, fingernails – that means the inability of transporting oxygen into the blood.


  • Water in the head:
  • Severe headache
  • Vomiting
  • Walking like an intoxicated (ataxia)
  • Mental confusion / altered mental status
  • Irritable – does not want to be bothered by other people
  • Unconsciousness or coma
  • Test: tandem walking test, heel to toe step. Fall off from the line.


Find out the main problem at altitude. Assume all problems are altitude sickness unless proven otherwise.

If it is an altitude problem with mild symptoms, stay at the same altitude until the symptoms are completely gone. An example – take an aspirin tablet, try to go up but listen to your body. If symptoms are worsening, descend.


  • Acclimatization – after a 1000m ascent, stay one more night for acclimatization.
  • Do not make a rapid ascend, don’t go too fast too high.
  • No alcohol, sleeping pills and smoking.
  • Drink more fluid 3-4 liters a day – clean water, boiled and filtered, or treated tea/coffee/soup/juice etc.
  • Do not carry heavy packs, 10-12 kgs ok.
  • Climb higher, always sleep lower.
  • Over 3000m, 300m ascent a day.
  • Never travel alone.


Descent is the best remedy; please do not wait for the helicopter


  • Oxygen
  • Diamox- for AMS- 125mg before dinner for sleeping problem if feeling suffocated.
  • Nafedipine- for HAPE
  • Steroids/Dexamethasone for ACE
  • Hyperbolic bag- Gammow bag


  • Awareness of Altitude illness
  • If you have mild symptoms, do not proceed higher. Take aspirin tablets.
  • If you have worsening symptoms, go down immediately.
  • Do not leave your team member behind unattended.


  • Go up slowly.
  • Drink plenty of fluids (at least 3 liters per day)
  • Before your trip, please refresh your knowledge about altitude sickness so that you can help yourself and others as well.

Drug prevention (prophylaxis)

Diamox (actazolamide) may be necessary for people going on rescue missions at high altitude or flying in to high altitude cities like La Paz or Lhasa. People with sulpha allergy should not take diamox, the primary drug for prevention, and further details are given below. A second drug, dexamethasone (see below) should also be carried, particularly if the destination is remote: this can be life saving if HACE supervenes

Acetazolamide (diamox): This is the most tried and tested drug for altitude sickness prevention and treatment. Unlike dexamethasone this drug does not mask the symptoms but actually treats the problem. It seems to works by increasing the amount of alkali (bicarbonate) excreted in the urine, making the blood more acidic. Acidifying the blood drives the ventilation, which is the cornerstone of acclimatization.

For prevention, 125 mg twice daily starting the evening before and continuing for three days once the highest altitude is reached, is effective. A recent article in the British Medical Journal suggested taking a higher dosage -- 750mg daily. Our experience in the Indian subcontinent has consistently been that 250 mg per day has been rewarding, while excessive dosage may just increase the side effects.

Side effects of diamox are: an uncomfortable tingling of the fingers, toes and face (called "jhum jhum" in Nepali); carbonated drinks tasting flat; excessive urination; and rarely, blurring of vision. In most of the treks in Nepal, gradual ascent is possible and prophylaxis tends to be discouraged. Certainly if trekkers develop headache and nausea or the other symptoms of AMS, then treatment with diamox is fine. The treatment dosage is 250 mg twice a day for about three days.

Dexamethasone: This steroid drug can be life saving in people with HACE, and works by decreasing swelling and reducing the pressure in the bony skull. The dosage is 4 mg three times per day, and obvious improvement usually occurs within about six hours. Like the hyperbaric bag (See below), this drug "buys time" especially at night when it may be problematic to descend. Descent should be carried out the next day. It is unwise to ascend while taking dexamethasone: unlike diamox this drug only masks the symptoms.

Dexamethasone can be highly effective: many people who are lethargic or even in coma will improve significantly after tablets or an injection, and may even be able to descend with assistance. Many pilgrims at the annual festival at Gosainkunda lake in Nepal suffer from HACE following a rapid rate of ascent, and respond remarkably well to dexamethasone. Mountain climbers also sometimes carry this drug to prevent or treat AMS. It needs to be used cautiously, however, because it can cause stomach irritation, euphoria or depression.

It may be a good idea to pack this drug for a high altitude trek for emergency usage in the event of HACE In people allergic to sulpha drugs (and therefore unable to take diamox) dexamethasone can also be used for prevention: 4 mg twice a day for about three days may be sufficient.

Nifedipine: This drug is generally used to treat high blood pressure, but also seems able to decrease the narrowing in the pulmonary artery caused by low oxygen levels, thereby improving oxygen transfer. It can therefore be used to treat HAPE, though unfortunately its effectiveness is not anywhere as dramatic that of dexamethasone in HACE. The dosage is 20 mg of long acting nifedipine, six hourly.

It can cause sudden lowering of blood pressure so the patient has to be warned to get up slowly from a sitting or reclining position. It has also been used in the same dosage to prevent HAPE in people with a past history of this disease.

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