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 (8200 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 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 grey 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.
How is altitude sickness 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 the 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 it 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 XL) 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 500 m (1600 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.
Can you prevent altitude sickness?
You may be able to prevent altitude sickness by taking your time when you go to high altitudes, using medicine in advance, and eating certain foods.
- If you are going to altitudes higher than 2500 m (8200 ft), try to spend 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. Examples of high-altitude cities include Cuzco, Peru; La Paz, Bolivia; and Lhasa, Tibet.
- Sleep at an altitude that is lower than the altitude you were at during the day. For example, if you ski at 2900 m (9500 ft) during the day, sleep the night before and the night after at 2500 m (8200 ft). "Climb high, sleep low" is standard practice for those who spend time at high altitudes.
- Studies show that starting to take ibuprofen 6 hours before climbing to high elevations and then taking it every 6 hours while climbing may help prevent altitude sickness.footnote 1, footnote 2 Ibuprofen may also reduce the symptoms of altitude sickness if you do get it.
- You may consider taking acetazolamide or possibly dexamethasone before going to a high altitude.footnote 3 Talk to your doctor about this.
- Eat a lot of carbohydrates. This includes breads, cereals, grains, and pasta.
What if you have a lung problem or other disease?
Experts do not know much about how altitude affects other diseases. Many people with allergic asthma do better at high altitudes. Still, if you have asthma and are going to high altitudes, continue to use your daily controller medicine and take your quick-relief medicine with you. Talk with your doctor about altitude sickness if you have long-term diseases, especially heart problems, sickle cell anemia, chronic obstructive pulmonary disease (COPD), or sleep apnea.
- Lipman GS, et al. (2012). Ibuprofen prevents altitude illness: A randomized controlled trial for prevention of altitude illness with nonsteroidal anti-inflammatories. Annals of Emergency Medicine, 59(6): 484–490.
- Pandit A, et al. (2014). Efficacy of NSAIDs for the prevention of acute mountain sickness: A systematic review and meta-analysis. Journal of Community Hospital Internal Medicine Perspectives, 4(4). Available online: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4185145. Accessed May 21, 2016.
- Murdoch D (2010). Altitude sickness, search date October 2009. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
Current as of: August 22, 2019
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
Current as of: August 22, 2019