What is altitude sickness?

Altitude sickness, also called mountain sickness, is a group of general symptoms that are brought on by climbing or walking to a higher and higher altitude (elevation) too quickly.

Who is at risk for altitude sickness?

Altitude sickness can affect anyone who goes to high altitudes without giving the body time to adjust to the changes in air pressure and oxygen level. High altitude is defined as 8,000 - 12,000 feet above sea level. Very high altitude is 12,000 - 18,000 feet, and altitudes above 18,000 feet are considered extremely high altitude. For comparison, New York City has an altitude of 33 feet, Indianapolis, Ind. has an altitude of 797 feet, Denver, Colo. (the “Mile-High City” ) is at 5,000 feet, and the Grand Canyon is 6,600 feet above sea level.

The more rapid a climb to high altitude, the more likely that altitude sickness will develop. Altitude sickness also is more likely to develop when climbs are more difficult and take more energy, compared with a slow and easy climb.

Age, sex and general health do not seem to make a difference in risk for altitude sickness. However, people with lung or heart disease may be told to avoid high altitudes. People who live at lower elevations and are not used to higher altitudes and people who have had altitude sickness previously seem to have a higher risk for altitude sickness.

Skiers, hikers and anyone planning a trip a location that is significantly higher than what they are used to should be know the signs and symptoms of altitude sickness and how to prevent and treat it.

Pregnant women should ask their doctor before traveling to a high altitude location.

Why does climbing too high too quickly cause problems?

This is because the body doesn’t have enough time to adapt to the lower air pressure and lower oxygen level in the air at high altitudes. The body responds by increasing the breathing rate. In turn, this boosts the blood oxygen, but not to normal levels. The body must adjust to operating with less oxygen than usual. When a person doesn’t give the body time to adjust, he or she will develop symptoms of altitude sickness.

What are the symptoms of altitude sickness?

Typical symptoms include headache, nausea, vomiting and lightheadedness. The different levels of altitude sickness have different symptoms:

Symptoms of mild, short-term altitude sickness also include dizziness, fatigue, shortness of breath, loss of appetite, sleep problems and a general loss of energy. Symptoms usually begin within 12 to 24 hours of arriving at a high altitude. Symptoms lessen within a day or two as the person gets used to the altitude.

Symptoms of moderate altitude sickness are more intense and are not relieved by over-the-counter medicines. Fatigue, weakness and shortness of breath worsen instead of improving over time. The affected person may start to show loss of coordination and have difficulty walking, severe headache that is not relieved by medicines, nausea and vomiting, and tightness or congestion in the chest. Normal activity is difficult, although the person may still be able to walk on his or her own.

Symptoms of severe altitude sickness include shortness of breath at rest, inability to walk, confusion and fluid buildup in the lungs and/or brain. Other symptoms may include cough and a gray, pale or bluish skin tone. Severe altitude sickness is an emergency situation, and the affected person must be taken to a lower altitude immediately.

Last reviewed by a Cleveland Clinic medical professional on 03/03/2017.


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