Acute Mountain Sickness (AMS)

Information on acute mountain sickness caused by low levels of oxygen to the brain.

    learn about levels of low oxygen and mountain sickness

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    1. What is Acute Mountain Sickness?
    2. What Causes Acute Mountain Sickness?
    3. Diagnosing Acute Mountain Sickness
    4. Help for Acute Mountain Sickness

    What is Acute Mountain Sickness?

    Acute mountain sickness (AMS) is also known as high altitude sickness. Acute mountain sickness occurs when a person rapidly increases their distance above the ground – usually when climbing, skiing or hiking higher than 6,000 feet above sea level. If the person is not used to high-altitudes (staying at a ski resort, riding in a hot air balloon or taking a hike after many years) they can experience acute mountain sickness.

    What Causes Acute Mountain Sickness?

    At a high altitude the air is said to be ‘thinner’. This means that the concentration of oxygen is less, and air pressure is reduced. This combination leads to acute mountain sickness. In the same way that one may feel light headed holding their breath, when oxygen is scarce, the brain is deprived of oxygen – and dizziness results. acute mountain sickness is also likely to occur if an accent is made very quickly or too fast.

    Height above 14,000 feet increases the risk of mild symptoms, but people who stay at this level for a prolonged time may develop more severe symptoms. The condition can be made worse as a person suffering from symptoms may become anxious or stressed, breathe quicker and hyperventilate – further exacerbating the situation.

    Diagnosing Acute Mountain Sickness

    Symptoms of acute mountain sickness can affect the nervous system, lungs, muscles, and heart.

    Symptoms of mild to moderate acute mountain sickness
    • Difficulty sleeping
    • Feeling dizzy or light-headed
    • Fatigue
    • Headaches
    • Loss of appetite (with or without nausea and/or vomiting)
    • Rapid heart race
    • Shortness of breath (when exerted)
    • Symptoms of more severe Acute Mountain Sickness include:
    • Discoloration of the skin (Blue tinge on face, fingernail beds, around the mouth)
    • Chest tightness or congestion
    • Confusion
    • Cough (with our without blood)
    • Withdrawal from social interaction
    • Gray or pale complexion
    • Inability to walk in a straight line (or cannot walk at all)
    • Shortness of breath (at rest)


     Note: Acute mountain sickness can be life-threatening if left un-treated, so contact your health care provider if symptoms develop— even if symptoms are resolved when returning to a lower altitude. If any severe symptoms (above) are experienced, seek medical advice immediately.

    Help for Acute Mountain Sickness

    Immediate treatment for mountain sickness involves descending to a lower altitude safely and slowly. If possible, supplementation with oxygen should be given if it is readily available. Certain prescribed drugs may be administered to stimulate breathing, but ensure adequate fluid intake, as these medications have been known to cause increased urination. Steroid drugs may be prescribed if there is swelling on the brain, but these medications may come with the added risk of side effects. In severe cases, a breathing machine may be used (respirator).

    Acute mountain sickness can be prevented with the right preventative medication. Before going on a trip, hike or climb where the altitude is higher than the altitude that you are used to, consult your health practitioner for advice on preventative medication.

    Tips Related to Acute Mountain Sickness:
    • Do not move to high altitude too quickly (take it slow while climbing, hiking or skiing)
    • Try not to over exert yourself – pace yourself and take regular breaks
    • Drink plenty of water per day while hiking
    • Try not to smoke, take alcohol or any anti-depressants (including sleeping pills) while you are at a high altitude
    • Eat a high carbohydrate diet while at altitude
    • Prevent the onset of the sickness by investigating preventative medication
    • Carry an oxygen supply (enough for several days) if you exceed 9,000 feet


    Tips for Someone with Acute Mountain Sickness
    • Rest in a quiet, dark environment where no noise or bright light is evident
    • Keep hydrated and drink lots of fluids
    • Seek medical advice if you experience any severe symptoms mentioned above