What is altitude sickness?
Altitude is the distance above sea level. As you go to higher altitudes, the air contains less oxygen.
Altitude sickness happens when you're at a height with less oxygen than you're used to. For many people this happens above 8,000 feet (2400 meters). Some people can go to much higher altitudes without getting symptoms.
The higher you go and the quicker you get there, the more likely you are to get altitude sickness
Most people just get headache, tiredness, an upset stomach, and trouble sleeping
Some people get a dangerous swelling of their brain or fluid buildup in their lungs
You treat altitude sickness by going down to a lower altitude
You can prevent altitude sickness by taking your time going up in altitude
Certain medicines also can help prevent altitude sickness
What are the types of altitude sickness?
There are 3 types of altitude sickness:
Acute mountain sickness: The mildest type of altitude sickness, with symptoms that usually last 1 or 2 days
High-altitude cerebral edema (HACE): An uncommon and sometimes fatal medical emergency that causes brain swelling
High-altitude pulmonary edema (HAPE): A severe and sometimes fatal medical emergency that causes breathing problems and fluid to fill your lungs
What causes altitude sickness?
Altitude sickness is caused by traveling to a high altitude where the air you breathe contains less oxygen. You have a greater chance of having symptoms if you travel to a higher altitude too quickly or if you sleep at a high altitude.
You're at increased risk for altitude sickness if:
You've had it before
You normally live at a very low altitude
You push yourself too hard (overexert)
Medical problems such as asthma, chronic obstructive pulmonary disease (COPD), and heart disease are NOT risk factors for altitude sickness. However, if you have a serious medical disorder, low oxygen levels at a high altitude can be dangerous.
What are the symptoms of altitude sickness?
Symptoms depend on what type of altitude sickness you have.
With acute mountain sickness, within 6 to 10 hours of traveling to over 8,000 feet you may have:
Headache
Light-headedness
Loss of appetite, upset stomach, or throwing up
Feeling tired, weak, or cranky
Trouble sleeping
Sometimes people mistake these symptoms for a hangover, migraine, extreme tiredness, or a viral infection.
High-altitude cerebral edema (HACE) causes brain swelling that can cause:
Headache
Confusion
Walking that is unsteady and clumsy
If not treated quickly, HACE can cause seizures, coma, and death.
High-altitude pulmonary edema (HAPE) may happen 24 to 96 hours after you travel quickly to a high altitude. Symptoms are worse at night when you lie down and may become more severe very quickly. HAPE causes lung problems such as:
Dry cough and shortness of breath after mild activity
Shortness of breath while resting
A bluish color in your skin, lips, and nails
Sometimes gasping for breath, coughing up pink or bloody mucus, and making gurgling sounds while breathing
If not treated quickly, HAPE can be fatal.
People who live at high altitudes may get HAPE when they return home after a brief stay at a lower altitude (this is called re-entry pulmonary edema).
Even if you don't have one of these types of altitude sickness, you may have symptoms from being at a high altitude such as:
Swelling of your hands, feet, and face—this is common and usually goes away in a few days
Headache, without other symptoms of acute mountain sickness
Small areas of bleeding in the back of the eye (retinal hemorrhages), after traveling above 9,000 feet
Retinal hemorrhages may sometimes cause a small blind spot in your vision, but the blind spot usually goes away after you travel to a lower altitude.
How can doctors tell if I have altitude sickness?
Doctors tell if you have altitude sickness based on your symptoms. They may also:
Listen to your chest with a stethoscope to see if you have fluid in your lungs
Do an x-ray of your chest
Test the amount of oxygen in your blood
How do doctors treat altitude sickness?
Treatment depends on your symptoms and what type of altitude sickness you have. The best first step in treatment for all types of altitude sickness is:
Going to a lower altitude
For mild symptoms, doctors will have you:
Rest
Avoid going to a higher altitude until symptoms disappear
Drink lots of fluids
For severe acute mountain sickness, doctors will:
Have you travel to a lower altitude
Give you extra oxygen
If symptoms are severe, and if traveling to a lower altitude isn't possible, doctors sometimes have you breathe pure oxygen while lying in a special high-pressure bag (hyperbaric oxygen therapy).
How can I prevent altitude sickness?
The best way to prevent altitude sickness is to travel to higher altitudes slowly so your body has time to adjust. The altitude at which you sleep has the greatest effect on you.
Being physically fit doesn't protect you from getting altitude sickness.
Most people easily adjust to altitudes of up to 8,000 feet (2,400 meters) without special precautions. But adjusting to higher altitudes, especially above 10,000 feet (3,000 meters), can take many days or weeks. To go to that height, climbers should only increase their sleeping altitude by about 500 to 1500 feet (300 or 500 meters) a day and should take a day off from climbing higher every 3 or 4 days.
Other ways to prevent altitude sickness:
Before you travel, ask your doctor about taking altitude medicines
Avoid heavy activity when you arrive at a high altitude location
Don't use alcohol, opioids, or sleep medicine
If you’ve had altitude sickness before, watch for signs you’re getting it again and travel to a lower altitude if needed.
