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 2500 m (8000 ft) 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 holiday or trek in high-altitude countries like Peru, Ecuador, or Nepal.
Altitude sickness is also called acute mountain sickness.
What causes it?
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, not being able to catch your breath even at rest, and having blue or grey lips or fingernails. 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.
How is it diagnosed?
If you are at a high altitude, your doctor may think you have this condition. Your doctor will ask you questions about your symptoms and examine you. To rule out other conditions, your doctor may ask if you have been drinking fluids or alcohol or using any medicines, or if you have a cold or influenza (flu).
If you are hiking or camping, you and those with you need to know the symptoms of altitude sickness. People often mistake altitude sickness for the flu, a hangover, or dehydration. As a rule, consider your symptoms to be altitude sickness unless you can prove they are not.
How is altitude sickness treated?
The best treatment for altitude sickness is to go to a lower altitude. But if you have mild symptoms, you may be able to stay at that altitude and let your body get used to it. Symptoms often occur if you have just arrived at a mountain resort from a lower altitude.
If you stay at a high altitude, rest. You can explore the area, but take it easy. Limit any walking or activity. Drink plenty of water, but do not drink alcohol. Do not go to a higher altitude until your symptoms go away. This may take from 12 hours to 3 or 4 days.
For the headache, you can take an over-the-counter medicine, such as ibuprofen (Advil, Motrin) or naproxen (Aleve). Do not give aspirin to anyone younger than 18. Aspirin has been linked to Reye syndrome, a serious illness. You may also use medicine to reduce feeling sick to your stomach or other symptoms.
A doctor can give you acetazolamide. This speeds up how fast your body gets used to the higher altitude. Nifedipine (Adalat) and dexamethasone are also used for altitude sickness. You may also be able to use oxygen or a specially designed pressure chamber to treat altitude sickness.
Go to a lower altitude if your symptoms are moderate to severe, they get worse, or medicine or oxygen treatment does not help. Go down at least 450 m (1500 ft). Go to a lower altitude as fast as you can or get emergency help if someone with you has severe symptoms such as being confused or not being able to walk straight. Go with the person. Never let someone with severe altitude sickness go down alone.
How can you prevent it?
You may be able to prevent altitude sickness by taking your time when you go to high altitudes and using medicine in advance.
- If you go to altitudes higher than 2,500 m (8,000 ft), try to spend at least a night at a medium altitude before going higher. For example, in Canada, spend a night in Banff before going to the Rocky Mountains.
- Do not fly into high-altitude cities. If this is not possible, avoid large meals, alcohol, and being very active after you arrive. Rest, and drink plenty of liquids. If you have symptoms, do not go higher until they have gone away.
- Sleep at an altitude that is lower than the altitude you were at during the day. For example, if you ski at 3,000 m (9,500 ft) during the day, sleep the night before and the night after at 2,500 m (8,000 ft).
- You may consider taking medicines such as ibuprofen, acetazolamide, or dexamethasone before travelling to high altitudes. These medicines may prevent or lessen symptoms. Talk to your doctor about this.
Current as of: July 6, 2021
Author: Healthwise Staff
Anne C. Poinier MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
W. David Colby IV MSc, MD, FRCPC - Infectious Disease
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