Altitude Sickness

Preventing Acute Mountain Sickness

Acute mountain sickness is caused by a lack of oxygen when traveling to higher elevations. This usually occurs in individuals exposed to an altitude over 7,000 feet (2,100 m) who have not had a chance to acclimate to the altitude before engaging in physical activities. Mountain climbers, trekkers, skiers, and travelers to the Andes or Himalayas are at greatest risk. While individual tolerance varies, symptoms usually appear in several hours, with those in poor physical condition being most susceptible. Headache, fatigue, shortness of breath, nausea, and poor appetite occur initially. Inability to sleep is also frequently reported. In more severe cases thinking and judgement may become impaired. An uncommon but potentially fatal complication called high altitude pulmonary edema, caused by fluid build-up in the lungs, can also occur.

The symptoms of acute mountain sickness can be prevented or minimized by gradually ascending (less than 500 meters/day)over several days to give your body a chance to acclimate to the higher altitude. Taking the prescription medication Diamox (acetazolamide) 250 mg three times a day has been shown to speed up the acclimatization process and can be taken shortly before and during the ascent. Do not take this medication if you are allergic to sulfa drugs. This medication is a mild diuretic and may work by changing the body's acid-base balance and stimulating breathing. Dexamethasone 8 mg once a day has also been shown to be effective. However, this steroid medication may have more adverse effects. Once symptoms occur, they usually improve over several days without treatment. However, if they become severe, they can be relieved with the administration of oxygen or descent to a lower altitude.

Gary P. Barnas, MD
Associate Professor
General Internal Medicine

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.