What Are Symptoms of Altitude Sickness?

Reviewed on 7/15/2022

Man out on a hike experiencing altitude sickness
Altitude symptoms may include headache, fatigue, loss of appetite, nausea and/or vomiting, feeling sick (malaise), dizziness, lightheadedness, shortness of breath, reduced performance, decreased coordination, and insomnia.

Altitude sickness occurs when people travel to a high altitude too quickly and breathing becomes difficult because of the inability to take in as much oxygen.

Altitude sickness can become a medical emergency if symptoms are ignored. 

Also called acute mountain sickness (AMS), altitude sickness does not just affect mountain climbers. It can affect people who normally live at or near sea level who travel to cities 8,000 feet (2,400 meters) above sea level or higher.

Symptoms of altitude sickness usually develop between six and 24 hours after reaching altitudes more than 8,000 feet above sea level.

Symptoms of altitude sickness may feel similar to those of a bad hangover and may include:

Symptoms are usually worse at night.

If initial symptoms of altitude sickness are ignored, potentially life-threatening conditions can occur:

  • High altitude cerebral edema (HACE) is swelling of the brain caused by a lack of oxygen
    • Additional symptoms of HACE include:
      • Weakness
      • Confusion
      • Hallucinations
  • High altitude pulmonary edema (HAPE) is a build-up of fluid in the lungs
    • Additional symptoms of HAPE include:
      • Blue tinge to the skin or lips (cyanosis)
      • Breathing difficulties, even at rest
      • Chest tightness 
      • Persistent cough, with pink or white frothy sputum
      • Weakness

What Causes Altitude Sickness?

The cause of altitude sickness is gaining altitude too quickly, which doesn't allow the body enough time to adjust to reduced oxygen and changes in air pressure. This results in a lack of oxygen reaching the tissues of the body.

Physical fitness does not decrease a person’s chances of developing a high-altitude illness. While it is not always possible to know in advance who may become ill when traveling to a high altitude, certain groups are at increased risk, such as people who:

  • Have a prior history of altitude sickness
  • Overexert themselves before adjusting to the change in altitude
  • Ascend rapidly (e.g., within one day) from low elevation to altitudes above 9,000 ft/2,750 m
  • Ascend rapidly (more than 1,640 to 3,280 ft/day [more than 500 to 1000 m/day] in sleeping altitude), when already above 9,000 ft/2,750 m
  • Have an underlying medical condition that affects breathing

What Is the Treatment for Altitude Sickness?

Symptoms of altitude sickness generally resolve within 12 to 48 hours of acclimatization at elevation. 

Treatment for altitude sickness includes: 

See a doctor if symptoms do not improve or worsen.

Treatment for high altitude cerebral edema (HACE) includes:

  • Descent to a lower altitude immediately
  • Dexamethasone to reduce brain swelling (often carried by professional mountain climbers as part of their medical supplies)
  • Bottled oxygen, if available
  • Seek medical treatment at a hospital as soon as possible for follow-up treatment

Treatment for high altitude pulmonary edema (HAPE) includes:

  • Descent to a lower altitude immediately
  • Nifedipine (Procardia XL, Adalat CC, Afeditab CR) to reduce chest tightness and make breathing easier (often carried by professional mountain climbers as part of their medical supplies)
  • Bottled oxygen, if available
  • Seek medical treatment at a hospital as soon as possible for follow-up treatment

How Do You Prevent Altitude Sickness?

The best way to prevent altitude sickness is to travel to high altitudes slowly. It usually takes 12 to 48 hours at elevation for the body to get used to a change in altitude.

In addition: 

  • When possible, avoid flying directly to areas of high altitude
  • Allow two to three days to acclimate to high altitudes before going above 8,000 feet
  • Don’t climb more than 1,000 feet to 1,600 feet per day
  • Include a rest day every 2,000 feet to 3,000 feet you climb, or rest every three to four days
  • Drink plenty of water
  • Don’t smoke or drink alcohol
  • Avoid strenuous exercise for the first 24 hours
  • Eat a light but high-calorie diet
  • Travelling with these medicines for altitude sickness:
    • Acetazolamide (Diamox) to prevent and treat high-altitude sickness
      • Begin taking one to two before starting to climb and continue to take it while going up
    • Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin) or naproxen (Aleve) or acetaminophen (Tylenol) for headaches
    • Ondansetron (Zofran) or promethazine (Phenergan, Promethegan, Phenadoz) for nausea


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Reviewed on 7/15/2022

Image sources: iStock Images