What Is Altitude Sickness?

Altitude sickness happens to some people when they travel to higher elevations, particularly at 8,000 to 10,000 feet above sea level. There aren’t many places in the U.S. that reach this altitude, and most of them are tall mountains in Colorado. But even more moderate elevations can cause symptoms. Altitude sickness is typically mild and temporary, provided you’re not ascending the world’s tallest peaks. Here we’ll explain why altitude sickness happens, the common symptoms, and how you can treat it.

Why does altitude sickness happen?

As you get farther away from sea level, there’s less oxygen in the air you breathe. Normally, your body can gradually adjust to these lower levels of oxygen — a process called acclimatizing. Altitude sickness occurs when your body hasn’t had enough time to adjust. We know altitude sickness is related to a change in the blood’s oxygen levels. But experts don’t know exactly why this causes temporary shifts in the body’s physiology. The symptoms of altitude sickness may be due to a sudden increase in blood flow to the brain and lungs to help send more oxygen to these organs.

What are symptoms of altitude sickness?

The symptoms of altitude sickness usually start a few hours after arriving at a higher altitude. Some of the the more common symptoms are:

• Headache

• Fatigue

• Poor appetite

• Nausea and vomiting

In most cases, altitude sickness isn’t serious, especially at more moderate elevations like mountain resorts. And it’s normal to experience these symptoms when you travel to destinations like a ski resort. 

People who travel to more extreme altitudes are at risk for rare but serious forms of altitude sickness: 

• High altitude cerebral edema (HACE) leads to swelling of the brain, and it can cause confusion, lethargy, and problems with coordination and balance.

• High altitude pulmonary edema (HAPE) leads to fluid collecting in the lungs, and it can cause severe shortness of breath and coughing up blood. 

These conditions are rare, and they don’t usually happen unless you’re going to extremely high altitudes, like climbers on Mount Everest. But if you notice your symptoms are severe or worsening, it’s best to see a healthcare provider or descend to a lower altitude, if possible.

Treatment for altitude sickness 

In most cases, altitude sickness will go away on its own after 1 to 2 days. The best way to recover is to rest as much as possible when you first arrive at a higher elevation. Traveling to a lower elevation will help with symptoms as well, but this is sometimes not possible or convenient. And it’s unnecessary if you feel like your symptoms are manageable. 

Some people, especially those traveling to more extreme altitudes, choose to take a medication called acetazolamide (Diamox). Acetazolamide helps by stabilizing the blood’s pH level, which occurs when you start to breathe faster in areas with lower oxygen. This in turn allows the lungs to bring in more oxygen without throwing off the acid levels in the blood. But most people don’t need this medication.

If you develop a more severe form of altitude sickness than those described above, there are some other treatments in addition to acetazolamide that can help:

• Supplemental oxygen can be given by a mask or nasal prongs.

• Dexamethasone reduces brain swelling and the amount of fluid in the lungs. 

• Nifedipine dilates blood vessels in the lungs to help remove the excess fluid.

These medications are rarely needed, and they’re typically reserved for the more serious HACE and HAPE conditions. 

Preventing altitude sickness

While you can’t change the altitude of your desired destination, there are some steps to help prevent altitude sickness:

• Give yourself 2 to 4 days at a slightly lower elevation to adjust to the altitude.

• Avoid exercising vigorously for the first 2 days after arriving at a high altitude.

• If you plan to travel to altitudes above 8,000 feet, it helps to descend at night so you can sleep at lower altitudes.

• Consider taking acetazolamide when you start your trip.

While these suggestions aren’t always realistic, they’re worth consideration to avoid any unpleasant symptoms, especially if you’re traveling for vacation.

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Written by:

Michael Dreis, MD

Dr. Dreis is an emergency medicine physician currently practicing in Milwaukee, Wisconsin. He went to medical school at the University of Wisconsin – Madison and completed his residency at Henry Ford Hospital in Detroit, Michigan.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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