Altitude sickness can develop when a person climbs a high mountain or travels to a place 2,000 meters (6,500 feet) or higher above sea level.

Altitude sickness or acute mountain sickness (AMS) includes a broad range of illnesses and their associated symptoms. Altitude sickness can affect anyone who ascends to an altitude of 2,000 meters (6,500 feet) or more. Altitude sickness can be anything from a mild headache to brain swelling and even death. It is something every person going to a high altitude area should know about before they ascend.

What is altitude sickness?


Altitude sickness is the attributing cause of any symptom, such as headache, nausea, confusion, coma and even death that is brought on by ascending into high altitude areas. It is a temporary illness alleviated when the affected individual descends back to lower altitudes.

What causes altitude sickness?

The causes of altitude sickness are still not fully understood. At altitudes of 2,000 meters or more, oxygen concentration remains the same, but doesn’t enter your body the same way it does at sea level; oxygen cannot get into your body in adequate amounts. One reason for this is decreased air pressure and this is the main cause that lies behind the development of altitude sickness.

The symptoms of altitude sickness

Symptoms of altitude sickness can range from the mild, headache or nausea, to the more severe symptoms like brain swelling, confusion, fluid on the lungs, severe difficulty breathing and even death. About 20% of people will develop a mild form of altitude sickness after ascending to heights of 2,000 meters or more, and after 4,200 meters (13,800 feet) the majority of people will experience some degree of altitude sickness.

At extremely high altitudes, severe forms of altitude sickness can develop. The two most severe forms of altitude sickness are pulmonary edema (fluid on the lungs) and cerebral edema (swelling of the brain). Pulmonary edema caused by high altitude is known as High Altitude Pulmonary Edema (HAPE) and cerebral edema is known as High Altitude Cerebral Edema (HACE).


HAPE and HACE are life-threatening situations and a steroid called dexamethasone can be used to alleviate symptoms until the affected individual can descend to lower altitudes. Many of the milder symptoms of altitude sickness can be managed without descent. With rest, some medicines to address the symptoms and drinking lots of water to combat dehydration, the descent can often be avoided.

Who is at risk for getting altitude sickness?

It is falsely believed that if a person is fit and healthy, they are unlikely to get altitude sickness. Altitude sickness can affect anyone at any time if they are at or above an altitude of 2,000 meters (6,500 feet). Hikers, skiers, mountain climbers, travelers, and tourists all have the possibility of developing altitude sickness.

There is one group more likely to get altitude sickness than others and this ‘at risk’ group is fit young men. This might seem strange, but the reason is very logical. Altitude sickness is more likely to come on if a person rapidly ascends. People overconfident in their fitness and ability tend to think they are unlikely to develop altitude sickness and therefore ascend more rapidly increasing the likelihood of developing altitude sickness.

Preventing altitude sickness

mountain hiking

The faster a person ascends and the harder the person pushes themselves, the higher the chances of developing altitude sickness. This also increases the chances of developing a more severe form of altitude sickness. New research is revealing the usefulness of Viagra in the treatment of altitude sickness but no conclusions have been made. Following the advice listed below is the best way to avoid altitude sickness.

  • A gradual ascent is the only way to prevent altitude sickness. After traveling to heights of 3,000 meters (9,840 feet) or more, the general rule of thumb is that you should not ascend more than 300 meters (980 feet) per day.
  • Do not exert yourself during the first 24 hours. No skiing, hiking or trekking during the first 24 hours decreases the chances of developing altitude sickness.
  • Do not drink alcohol or use tobacco while at high altitudes. Alcohol can cause further dehydration and tobacco reduces oxygen exchange, making shortness of breath and respiratory difficulty much greater. Alcohol and tobacco can make altitude sickness worse than normal.
  • Stay properly hydrated. Becoming dehydrated at high altitudes will bring on altitude sickness much faster. Start drinking plenty of water prior to ascending to high altitude areas. If you arrive in a high altitude area and you are already dehydrated, you will have a greater chance of developing altitude sickness or making altitude sickness worse.

Treating high altitude sickness

mountain hiking

There is really only one way to treat altitude sickness and that is descent. Most of the mild cases of altitude sickness can be treated without descent, but if symptoms do not subside or worsen, descent is required. Severe altitude sickness, such as HAPE or HACE, are life-threatening situations that require medical attention and descent ASAP.

Trekking in high altitude areas, such as Tibet in the Himalayas or South America can be very adventurous, but medical emergencies in foreign countries can be extremely costly and turn an adventure into a disaster. Seek medical advice before you leave and if you develop altitude sickness and you are not sure what to do contact a medical professional before severe altitude sickness develops.