Acute Mountain Sickness

Acute Mountain Sickness (AMS) is a pathological effect of high altitude caused by exposure to low partial pressure of Oxygen. It typically occurs at about 8,000 feet, or 2,400 meters above sea level. Most instances of altitude sickness are mild and heal quickly. AMS is a mild type of altitude sickness.

Risk factors include a prior episode of altitude sickness, a high degree of activity, and a rapid increase in altitude. Prevention is done by gradually increasing elevation by no more than 300 metres (1,000 ft) per day. Being physically fit does not decrease the risk. Mild cases may be helped by Ibuprofen, Acetazolamide, or Dexamethasone (pain relief medicines).


Acute mountain sickness is caused by reduced air pressure and lower oxygen levels at high altitudes. You are at higher risk for acute mountain sickness if:

  • You live at or near sea level and travel to the high altitude.
  • You have had the illness before.
  • You ascend quickly.
  • You are not accustomed to the altitude.
  • Alcohol or other substances have interfered with accustomization.
  • You have medical problems involving the heart, nervous system, or lungs.


Mild symptoms include

  • Difficulty in sleeping
  • Fatigue
  • Headache
  • Nausea

Severe AMS includes

  • Pale complexion and skin discoloration
  • Inability to walk
  • Chest congestion


There are recommended ways to adjust to these conditions:

  • Spend at least one night at an ‘intermediate’ elevation below 3000 metres.
  • Above 3000 metres, increase your sleeping altitude by only 300-500 metres per day, and take a rest day for every 1000 metres of elevation.
  • If possible, do not fly or drive directly to high altitude.
  • If you go directly to high altitude, do not overexert yourself or move higher for the first 24 hours.


Treatment for acute mountain sickness varies depending on its severity.

  • Basic Treatment
    • You can avoid complications by steadily returning to a lower altitude.
    • Hospitalization is necessary if your doctor determines that you have brain swelling or fluid in your lungs.
    • You may receive oxygen if you have breathing issues.
  • Medication for altitude sickness include:
    • Acetazolamide, to correct breathing problems
    • Blood pressure medicine
    • Lung inhalers
    • Dexamethasone, to decrease brain swelling
    • Aspirin, for headache relief