Key Points

  • High altitude sickness results from a sudden drop of oxygen supplies following a rapid ascension to high altitudes.
  • Symptoms develop soon after arriving at a destination and include headaches, fatigue, and nausea.
  • If you have medical problems, a history of altitude sickness, and if you cannot avoid rapid ascent to altitudes above 2800 meters, seek a medical consultation prior to your trip.

Altitude Sickness

High Altitude Illness (HAI) is a very significant medical risk, especially with abrupt ascent above 2,500 meters. As altitude increases, barometric pressure and the amount of oxygen available for vital functions decrease. Colder temperatures will make one even more vulnerable. Therefore, commercial aircraft are pressurized to approximate the barometric pressure at 2500 meters (8000 feet). Some people will have mild HAI even at that altitude; about 25% will experience symptoms at 2,800 meters and most experts advise that severe High Altitude Illness could develop at 3,500 meters.


Symptoms can develop as quickly as one to two hours after landing and will usually begin within 6 hours; however, onset can even be delayed for up to 24 hours. The classic symptoms include

  • Headache
  • Fatigue
  • Light-headedness
  • Loss of appetite
  • Nausea
  • Vomiting
  • Disturbed sleep (often associated with frequent awakening)
  • Mild to severe shortness of breath with exertion.

High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE) are more severe forms of the disease.

At Risk

Persons at greatest risk are

  • Those with a history of HAI,
  • Those struggling with obesity
  • Females
  • Those with medical conditions such as problems with circulation, heart disease and chronic lung disease.

A proven recipe for disaster is rapid ascent combined with vigorous exercise before your body has a chance to adjust. Ironically, the risk among those aged 60 or older is less than average.


  • Make sure that set aside time to adjust after landing in high-altitude destinations
  • Reduce your activity level for the first 24 to 48 hours
  • Carry the basic drugs (acetaminophen, Gravol) for treatment of symptoms.

Diamox or acetazolamide, a time-honored drug used to prevent HAI. Research has demonstrated that starting treatment a day prior to rapid ascent will aid in the acclimatization of the body. At your travel health consult, {include hyperlink to APPOINTMENTS page} ask the doctor about this medication.


Treatment will vary depending on how severe the symptoms are.

  • Take it easy for the first 24 to 48 hours. The body will naturally start managing the challenge by increasing its respiratory rate.
  • Alcohol is strictly forbidden.
  • Basic medications such as Gravol and acetaminophen are permissible and helpful for treating mild symptoms.
  • When feasible, descend to a lower altitude; otherwise, oxygen therapy might be necessary.

Other treatments are available for more severe cases.

For more information:

Centres for Disease Control and Prevention:
Committee to Advise on Tropical Medicine And Travel:
American Heart Association:

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Since 1936, International Medical Services (IMS) has strategically promoted safety and travel illness prevention. We have extensive experience sending short and long term expatriates to every continent and major travel destination (including Antarctica).

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