Symptoms of altitude sickness are caused by the lower levels of oxygen available at higher elevations. Although the human body can adjust to changes in altitude, the process (called acclimatization) takes time. Symptoms of altitude illness occur during ascent, not descent. Each person has their own "acclimatization line." For most people, this line initially lies somewhere near 9,000 feet (2,700) meters).


To avoid or reduce the symptoms of altitude illness:


  1. Acute Mountain Sickness (AMS) typically appears at altitudes above 8,000 feet (2,400 meters), though illness can begin at elevations as low as 5,000 feet (1,500 meters) in some individuals. Symptoms usually appear within a few hours of ascent, and may include one or many of the following:

  2. If you experience mild APS symptoms, limit your activity level and remain at the same altitude for a day or two before resuming the climb. Aspirin or ibuprofen can be used for headache. If symptoms become worse during a day of rest. It is very important to descend until you begin to improve.

    The sulfa drug acetazolamide has been shown to prevent or lessen APS symptoms by increasing breathing rate and helping with acclimatization. For prevention, 125-250 mg twice a day is commonly recommended, to be started the day before the ascent and continued for several days at altitude.

  3. High Altitude Cerebral Edema (HACE) can be thought of as a worsening of AMS symptoms, with the addition of changes in consciousness and/or a loss of coordination as intracranial pressure increases. Symptoms are:

    • Hallucinations
    • Confusion
    • Beginning to stumble or stagger
    • Severe headaches
    • Incapacitating fatigue

    This is a dangerous form of altitude illness, and it can lead to coma and death.

    It is crucial for the victim to descend and receive drug and oxygen treatment.

  4. High Altitude Pulmonary Edema (HAPE) is a buildup of fluid in the lungs that can occur along with HACE or as a separate illness. It is a medical emergency.
    Symptoms are:

    • Breathlessness
    • Feeling very tired when walking
    • A sense of fullness or pressure in the chest

    When victims become short of breath, even while resting, the illness can rapidly progress to death. Victims must be guided back down and receive drug and oxygen treatment as soon as their illness is recognized as HAPE.

    Danger signs include severe headache, extreme fatigue or breathlessness (especially while resting), and any neurological problems such as stumbling, confusion, poor judgement or changes in consciousness.

    It is crucial to descend until symptoms begin to diminish if these signs are present.


Flying or driving directly to a mountain destination does not allow the human body enough time adjust to the altitude. Every attempt should be made to plan your trip to include days spent at transitional altitudes. There is a good chance that those who have had altitude illness once will have it again at high elevations. If you have had altitude problems previously, if you have heart or lung problems, or if you are planning to go to extremely high altitudes, consult your health care provider to discuss your options for prevention and treatment of illness.