About Altitude Sickness

Source:  "Non-Physician Altitude Tutorial"

As Nangchen is a land of high passes, most foreign visitors are strongly advised to acclimatize. Symptons of Acute Mountain Sickness (AMS) may occur, depending on individual visitor's physical health conditions; people who smoke and drink excessively would normally have more difficulties. AMS symptons are: loss of appetite, nausea or vomiting; fatigue or weakness; dizziness or light-headedness; difficulty in sleeping. AMS has been likened to a bad hangover, or worse. However, because the symptoms of mild AMS can be somewhat vague, a useful rule-of-thumb is: if you feel unwell at altitude, it is altitude sickness unless there is another obvious explanation (such as diarrhea).

The mainstay of treatment of AMS is rest, fluids, and mild analgesics: acetaminophen (paracetamol), aspirin, or ibuprofen. These medications will not cover up worsening symptoms. The natural progression for AMS is to get better, and often simply resting at the altitude at which you became ill is adequate treatment. Improvement usually occurs in one or two days, but may take as long as three or four days. Descent is also an option, and recovery will be quite rapid.

A frequent question is how to tell if a headache is due to altitude. Altitude headaches are usually nasty, persistent, and frequently there are other symptoms of AMS; they tend to be frontal (but may be anywhere), and may worsen with bending over. However, there are other causes of headaches, and you can try a simple diagnostic/therapeutic test. Dehydration is a common cause of headache at altitude. Drink one liter of fluid, and take some acetaminophen or one of the other analgesics listed above. If the headache resolves quickly and totally (and you have no other symptoms of AMS) it is very unlikely to have been due to AMS.

Dealing with Altitude Sickness


Acetazolamide (Diamox®) is a medication that forces the kidneys to excrete bicarbonate, the base form of carbon dioxide; this re-acidifies the blood, balancing the effects of the hyperventilation that occurs at altitude in an attempt to get oxygen. This re-acidification acts as a respiratory stimulant, particularly at night, reducing or eliminating the periodic breathing pattern common at altitude. Its net effect is to accelerate acclimatization. Acetazolamide isn't a magic bullet, cure of AMS is not immediate. It makes a process that might normally take about 24-48 hours speed up to about 12-24 hours.

Acetazolamide is a sulfonamide medication, and persons allergic to sulfa medicines should not take it. Common side effects include numbness, tingling, or vibrating sensations in hands, feet, and lips. Also, taste alterations, and ringing in the ears. These go away when the medicine is stopped. Since acetazolamide works by forcing a bicarbonate diuresis, you will urinate more on this medication. Uncommon side effects include nausea and headache. A few trekkers have had extreme visual blurring after taking only one or two doses of acetazolamide; fortunately they recovered their normal vision in several days once the medicine was discontinued.

Acetazolamide Use & Dosage:

For treatment of AMS

A dosage of 250 mg every 12 hours. The medicine can be discontinued once symptoms resolve. Children may take 2.5 mg/kg body weight every 12 hours.

For Periodic Breathing Difficulties

125 mg about an hour before bedtime. The medicine should be continued until you are below the altitude where symptoms became bothersome.


Dexamethasone (Decadron®) is a potent steroid used to treat brain edema. Whereas acetazolamide treats the problem (by accelerating acclimatization), dexamethasone treats the symptoms (the distress caused by hypoxia). Dexamethasone can completely remove the symptoms of AMS in a few hours, but it does not help you acclimatize. If you use dexamethasone to treat AMS you should not go higher until the next day, to be sure the medication has worn off and is not hiding a lack of acclimatization.

Side effects include euphoria in some people, trouble sleeping, and an increased blood sugar level in diabetics.

Dexamethasone Use & Dosage:

For treatment of AMS

Two doses of 4 mg, 6 hours apart. This can be given orally, or by an injection if the patient is vomiting. Children may be given 1 mg/kg of body weight, up to 4 mg maximum; a second dose is given in 6 hours. Do not ascend until at least 12 hours after the last dose, and then only if there are no symptoms of AMS.



AMS symptoms resolve very rapidly (minutes) on moderate-flow oxygen (2-4 liters per minute, by nasal cannula). There may be rebound symptoms if the duration of therapy is inadequate - several hours of treatment may be needed.


A Review of the AMS treatment options:

  • Descent


Rapid recovery: trekkers generally improve during descent, recover totally within several hours.


Loss of "progress" toward trek goal; descent may be difficult in bad weather or at night; personnel needed to accompany patient.

  • Rest at same elevation


Acclimatization to current altitude, no loss of upward progress.


It may take 24-48 hours to become symptom-free.

  • Rest plus acetazolamide


As with rest alone, plus acclimatization is accelerated, recovery likely within 12-24 hours.


Recovery may take 12-24 hours; side effects of acetazolamide.

  • Rest plus dexamethasone


Faster resolution of symptoms than with acetazolamide (usually in a few hours); minimal side effects; cheap.


Can hide symptoms & thus give a false sense of security to those who want to continue upwards. Does not accelerate acclimatization.

  • Rest plus dexamethasone & acetazolamide


Fast resolution of symptoms from the dexamethasone, plus improved acclimatization from the acetazolamide.


Side effects of acetazolamide. Same cautions as above regarding ascent after taking dexamethasone.

Preventing AMS

The key to avoiding AMS is a gradual ascent that gives your body time to acclimatize. People acclimatize at different rates, so no absolute statements are possible, but in general, the following recommendations will keep most people from getting AMS:

  • If possible, you should spend at least one night at an intermediate elevation below 3000m.
  • At altitudes above 3000m (10000ft), your sleeping elevation should not increase more than 300-500m (1000-1500ft) per night.
  • Every 1000m (3000ft) you should spend a second night at the same elevation.

Things to Avoid

Respiratory depression (the slowing down of breathing) can be caused by various medications, and may be a problem at altitude. The following medications can do this, and should never be used by someone who has symptoms of altitude illness (these may be safe in persons who are not ill, although this remains controversial):

  • Alcohol
  • Sleeping pills (acetazolamide is the sleeping tablet of choice at altitude)
  • Narcotic pain medications in more than modest doses


Under certain circumstances, prophylaxis with medication may be advisable.

  • For persons on forced rapid ascents (such as flying into Leh directly from Delhi) 
  • For persons who have repeatedly had AMS in the past


Acetazolamide is not recommended as a prophylactic medication, except under the specific limited conditions outlined above. Most people who have a reasonable ascent schedule will not need it, and in addition to some common minor but unpleasant side effects it carries the risk of any of the severe side effects that may occur with sulfonamides.

The dose of acetazolamide for prophylaxis is 125-250 mg twice a day starting 24 hours before ascent, and discontinuing after the second or third night at the maximum altitude (or with descent if that occurs earlier). Sustained release acetazolamide, 500 mg, is also available and may be taken once per day instead of the shorter acting form, though side effects will be more prominent with this dose.

AMS Prophylaxis:

Acetazolamide (Diamox®)

125-250 mg (depending on body weight; persons over 100 kg (220 lbs) should take the higher dose) twice a day starting 24 hours before ascent, and discontinuing after the second or third night at the maximum altitude (or with descent if that occurs earlier). Children may take 2.5 mg/kg of body weight twice a day.




If you feel unwell at altitude it is altitude illness until proven otherwise.



Never ascend with symptons of AMS


If you are getting worse, go down at once.

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