High-Altitude Illness

Last Updated October 2020 | This article was created by familydoctor.org editorial staff and reviewed by Deepak S. Patel, MD, FAAFP, FACSM

What is high-altitude illness?

High-altitude illness, or sickness, is a condition that can occur when you travel to a high altitude, such as the mountains. It’s also called mountain sickness. It usually happens at altitudes higher than 8,000 feet. At this altitude, there’s less oxygen. When you go from low to high altitudes, your body needs time to adjust to the change in oxygen levels. Therefore, high-altitude illness happens when your body doesn’t get enough oxygen.

Talk to your doctor if you plan to travel to altitudes.

Symptoms of high-altitude illness

Symptoms of high-altitude illness usually begin 12 to 24 hours after you reach a high altitude. Early symptoms include:

  • Headache
  • Dizziness
  • Nausea
  • Trouble breathing when active
  • Weakness or fatigue
  • Trouble sleeping
  • Increased heart rate

If you have these symptoms, stop, rest, and drink water. You may need to go back down to a lower altitude until your symptoms go away.

More severe symptoms include:

  • Trouble breathing at rest
  • Chest tightness or pain
  • Coughing
  • Vomiting
  • Confusion
  • Inability to walk in a straight line
  • Pale, gray, or blue skin

If you have these symptoms, go to a lower altitude right away and get medical help. Symptoms that are ignored or left untreated can be life threatening.

What causes high-altitude illness?

You may have heard that the air is “thinner” at higher altitudes. This means that your body can’t get as much oxygen. High-altitude illness most often occurs at altitudes higher than 8,000 feet. It can cause problems for people whose bodies aren’t used to working on so little oxygen.

There are 3 main types of high-altitude illness.

  • Acute mountain sickness:This is the most common form of the condition. It’s often mild and short-term.
  • High-altitude pulmonary edema (HAPE):This condition causes your lungs to swell with fluid, which can be fatal. It occurs at extreme high altitudes.
  • High-altitude cerebral edema (HACE):This condition causes your brain to swell with fluid, which can be fatal. It occurs at extreme high altitudes.

Everyone is at risk for high-altitude illness. Children and older adults are at an increased risk because it takes their bodies longer to adjust. You also may be at a greater risk if you:

  • Live in a place with a low altitude and travel to a place with a high altitude
  • Live in a place that has a high altitude
  • Climb or ascend altitudes too quickly.
  • Are dehydrated.
  • Have had high-altitude illness before.
  • Have a health condition that makes it hard to breathe normally.

How is high-altitude illness diagnosed?

People who have symptoms of high-altitude illness should see a doctor. Be sure to tell him or her about the conditions you were in when you had the symptoms. Your doctor will do a physical exam. Based on the severity of your symptoms, he or she may order tests. Tests may include a chest X-ray, brain scan, or electrocardiogram (ECG). These help diagnose the type of illness and decide on a treatment plan.

Can high-altitude illness be prevented or avoided?

There are 3 important things you can do to prevent high-altitude illness.

  • Take your time traveling to higher altitudes. It takes several days for your body to fully adjust to lower amounts of oxygen at high altitudes. This is true even for people who are healthy. Most people can safely go from sea level to an altitude of 8,000 feet in a few days. Once you reach 8,000 feet, you shouldn’t go up more than 1,000 to 2,000 feet per day. The higher you get, the longer it takes your body to adjust. Plan your trip so your body has time to get used to the high altitude before you start your physical activity.
  • Sleep at a low altitude, if possible.For example, if you ski at 10,000 feet during the day, sleep at a lower elevation at night. This lets your body rest and recover while you sleep.
  • Hydrate before, during, and after you travel. Dehydration can increase your risk of high-altitude illness. You should drink extra water several days before and after you travel. Make sure you pack enough water while you’re active. Avoid or limit the amount of alcohol you consume.

High-altitude illness treatment

It’s important to treat high-altitude illness as soon as symptoms begin. The first thing you should do is to safely go down to a lower altitude right away. If your symptoms are mild, you may be able to stay at that altitude and let your body adjust. If you do this, don’t exercise. Rest and drink water until you feel better. It may help to use a device that provides extra oxygen.

If needed, your doctor may prescribe medicine to prevent or treat symptoms. One example is acetazolamide. When taking this medicine, drink a lot of water and avoid alcohol.

If your symptoms are severe, continue to go down to a lower altitude until you’re no longer sick. If your symptoms don’t improve or get worse, call a doctor or go to the nearest hospital. You will need medical treatment.

Living with high-altitude illness

Don’t ignore signs of high-altitude illness. Symptoms that are ignored or left untreated can be life threatening. Don’t go higher until you feel better and your symptoms have gone away completely. Once your body adjusts, it should eventually get used to the low oxygen level. Over time, you shouldn’t get sick anymore. This is helpful for people who move to a higher altitude to live.

Is it safe to go to a high altitude if I have a chronic illness?

If you have a chronic illness, talk to your doctor before you travel to a high altitude. Depending on the type and severity of your chronic illness, your doctor can let you know if it’s safe for you to travel there.

Most people who have heart or lung disease can safely spend time at a high altitude if their condition is under control. Likewise, it’s usually safe for people who have coronary artery disease, mild emphysema, or high blood pressure to travel to a high-altitude. You won’t make those diseases worse by being there. Being overweight also doesn’t increase your risk.

However, high altitudes can be very dangerous for people who have:

  • Sickle cell anemia
  • Chronic obstructive pulmonary disease (COPD)
  • Severe emphysema
  • Severe heart disease

Is it safe to go to a high altitude during pregnancy?

There is little information about the risk of high-altitude illness during pregnancy. Some experts recommend that pregnant women not travel to an altitude higher than 8,000 feet. If you’re pregnant, ask your doctor for advice before you travel to a high altitude.

Is it safe for children to go to high altitudes?

Generally, it’s safe for children to go to high altitudes. However, they’re more likely to get high-altitude illness because their bodies have a hard time adjusting to the low oxygen level. Kids also may not be able to recognize the symptoms of high-altitude illness. That’s why it’s important for parents and other adults to carefully watch for signs of the illness in children.

Questions to ask your doctor

  • I’m traveling to a place with high altitudes. How can I prevent high-altitude illness?
  • If I am pregnant or have a chronic condition, are high altitudes safe for me?
  • How much water should I drink before I travel? How much water should I drink while in high altitudes?
  • I’m moving to a place with high altitudes. What’s the best way to prepare my body and adjust to the low oxygen level?