High Altitude Sickness - How, When & Prevent
What is altitude sickness?
Altitude sickness occurs when you cannot get enough oxygen from the air at high altitudes. This causes symptoms such as a headache, loss of appetite, and trouble sleeping. It happens most often when people who are not used to high altitudes go quickly from lower altitudes to 8000 ft (2438 m) or higher. For example, you may get a headache when you drive over a high mountain pass, hike to a high altitude, or arrive at a mountain resort.
Mild altitude sickness is common. Experts do not know who will get it and who will not. Neither your fitness level nor being male or female plays a role in whether you get altitude sickness.
Altitude sickness can be dangerous. It is smart to take special care if you go high-altitude hiking or camping (like in the Rockies) or have plans for a vacation or trek in high-altitude countries like Peru, Ecuador, or Nepal.
Altitude sickness is also called acute mountain sickness.
What causes altitude sickness?
Air is "thinner" at high altitudes. When you go too high too fast, your body cannot get as much oxygen as it needs. So you need to breathe faster. This causes the headache and other symptoms of altitude sickness. As your body gets used to the altitude, the symptoms go away.
What are the symptoms?
The symptoms of altitude sickness include:
- A headache, which is usually throbbing. It gets worse during the night and when you wake up.
- Not feeling like eating.
- Feeling sick to your stomach. You may vomit.
- Feeling weak and tired. In severe cases, you do not have the energy to eat, dress yourself, or do anything.
- Waking up during the night and not sleeping well.
- Feeling dizzy.
Your symptoms may be mild to severe. They may not start until a day after you have been at a high altitude. Many people say altitude sickness feels like having a hangover.
Altitude sickness can affect your lungs and brain. When this happens, symptoms include being confused, not being able to walk straight (ataxia), feeling faint, and having blue or gray lips or fingernails. When you breathe, you may hear a sound like a paper bag being crumpled. These symptoms mean the condition is severe. It may be deadly.
If you are going on a high-altitude trek, learn about altitude sickness, its symptoms, and how to treat it. Look out for other people in your group. You can learn more about altitude sickness at the International Society for Mountain Medicine website at www.ismmed.org.
Preventing altitude sickness
Proper acclimatisation to altitudes of about 2,500m (just over 8,200 feet) or more is the best way to prevent altitude sickness. It usually takes a few days for the body to get used to a change in altitude.
Ascending slowly will give your body time to adapt to the change in altitude. For example, once you're above 3,000m (10,000 feet) try not to increase the altitude at which you sleep by more than 300-500m a night. Keeping hydrated is also important, but make sure you avoid alcohol.
Who's affected by altitude sickness?
Altitude sickness is fairly common among those who spend time at high altitudes, such as mountaineers and skiers.
In its mildest form, altitude sickness can occur at heights over about 2,500m (8,000 feet) above sea level, which is a common height for many ski resorts.
However, the more severe symptoms of altitude sickness tend to occur at altitudes of 3,600m (about 12,000 feet) and above.
It's not possible to get altitude sickness in the UK because the highest mountain, Ben Nevis in Scotland, is only 1,344m (4,406 feet) high.
There are no specific factors, such as age, sex or physical fitness, that increase a person's likelihood of getting altitude sickness. Certain people are affected, while others are less susceptible to it. Just because you haven't had it before doesn't mean you won't develop it on another trip.