Altitude Sickness

Search Knowledgebase

Topic Contents

Altitude Sickness

Topic Overview

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 2400 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. Being male or female and your fitness level play no 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. 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 lazy. 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

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, not getting enough fluids, or feeling tired. 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.

You may also be able to use oxygen or a specially designed pressure chamber to treat altitude sickness.

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 acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve). Do not give ASA to anyone younger than 20. ASA 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 (Acetazolam). 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 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.

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 go to altitudes higher than 2400 m (8000 ft), try to spend a night at a medium altitude before going higher. For example, in Canada, spend a night in Banff before going higher in the Rockies.
  • 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 (9000 ft) during the day, sleep the night before and the night after at 2400 m (8000 ft). "Climb high, sleep low" is standard practice for those who spend time at high altitudes.
  • You may consider taking acetazolamide (Acetazolam) or possibly dexamethasone before going to a high altitude.1 Talk to your doctor about this.
  • Eat a lot of carbohydrate. 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 usual medicine and take your reliever 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.

Other Places To Get Help


International Society for Mountain Medicine
P.O. Box 31142
Colorado Springs, CO  80931-1142
Phone: (719) 572-1372
Fax: (719) 572-1514
Web Address:

The International Society for Mountain Medicine encourages research on all aspects of mountains, mountain peoples, and mountaineers. The Web site has information on altitude sickness and altitude sickness in children.

International Society of Travel Medicine
315 W Ponce de Leon Avenue
Suite 245
Decatur, GA  30030
Phone: (404) 373-8282
Fax: (404) 373-8283
Web Address:

The International Society of Travel Medicine (ISTM) provides education, service, and research in the field of travel medicine. ISTM focuses on preventive and curative medicine, infectious diseases, high altitude physiology, and travel-related obstetrics. Two other areas of focus are military medicine and migration medicine. ISTM's goals are to promote travel health, develop guidelines for travel medicine, and educate health professionals and people who work in the travel industry. ISTM's website has a travel clinic directory where travelers can search for a travel clinic near them.

Travel Health Information (Canada)
Public Health Agency of Canada
Web Address:

The Public Health Agency of Canada's Travel Health Web site provides travel health information for persons travelling outside Canada, including current information on international disease outbreaks, immunization recommendations for international travel, general health advice for international travellers, and disease-specific treatment and prevention guidelines. Information can be accessed 24 hours a day through the Travel Health Web site.



  1. Murdoch D (2010). Altitude sickness, search date October 2009. Online version of BMJ Clinical Evidence:

Other Works Consulted

  • Hackett PH, Roach RC (2007). High-altitude medicine. In PS Auerbach, ed., Wilderness Medicine, 5th ed., pp. 2–36. Philadelphia: Mosby Elsevier.
  • Luks AM, et al. (2010). Wilderness Medical Society consensus guidelines for the prevention and treatment of acute altitude sickness. Wilderness and Environmental Medicine, 21(2): 146–155.


By Healthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer W. David Colby IV, MSc, MD, FRCPC - Infectious Disease
Last Revised May 31, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.