Altitude sickness, also known as acute mountain sickness (AMS), is a condition that can occur when a person travels to a high altitude too quickly and the body does not get enough oxygen. It most commonly develops at elevations above 2,500 metres (8,000 feet), although some people may develop symptoms at lower altitudes. At high elevations, the air contains less oxygen. The body needs time to adjust to this reduced oxygen level, a process known as acclimatization. Rapidly ascending without allowing enough time for acclimatization increases the risk of altitude sickness. Altitude sickness is usually mild and improves with rest and acclimatization. However, in some cases it can become severe and develop into potentially life-threatening conditions such as high-altitude cerebral edema (HACE) or high-altitude pulmonary edema (HAPE). Prompt medical attention is essential if severe symptoms develop.
The main cause of altitude sickness is rapid exposure to reduced oxygen levels at high altitude. As altitude increases, atmospheric pressure decreases and the amount of oxygen available to the body decreases. When a person ascends too quickly, the lungs and other organs may not have enough time to adapt. Factors that can increase the risk include:
Rapid ascent to high altitude
Sleeping at a high altitude soon after arriving
Previous history of altitude sickness
Strenuous physical activity soon after reaching high altitude
Travelling to very high elevations without adequate acclimatization
Altitude sickness can affect anyone, regardless of age, gender, physical fitness or previous experience at high altitude.
Altitude sickness is generally diagnosed based on a person’s symptoms, recent travel history and altitude exposure. A healthcare professional may assess:
The altitude reached
How quickly the person ascended
When symptoms began
Severity and progression of symptoms
Breathing, heart rate and oxygen saturation
Neurological signs such as balance, coordination and mental alertness
Additional tests may be required when a healthcare professional suspects complications or another medical condition.
Treatment depends on the severity of the symptoms. For mild altitude sickness, recommended measures may include:
Stop ascending and rest
Allow the body time to acclimatize
Drink adequate fluids
Avoid alcohol and sedative medicines unless specifically prescribed
Avoid strenuous physical activity
Descend to a lower altitude if symptoms worsen or do not improve
For moderate or severe symptoms, descent should not be delayed. Oxygen therapy and medications may also be used by healthcare professionals when appropriate. Severe altitude-related conditions such as HACE and HAPE require emergency treatment.
The best way to prevent altitude sickness is gradual ascent and proper acclimatization. Helpful measures include:
Ascend gradually rather than rapidly
Allow adequate time for acclimatization
Avoid strenuous exercise immediately after reaching a higher altitude
Stay properly hydrated, but avoid excessive fluid intake
Avoid alcohol during the initial period of acclimatization
Do not ignore early symptoms
If symptoms become worse, do not continue ascending
People with a history of altitude sickness may need to discuss preventive medication with a healthcare professional before travelling to high altitudes.
Consult a healthcare professional if symptoms of altitude sickness develop and do not improve with rest and acclimatization. Emergency medical care is required for severe breathlessness, confusion, difficulty walking, loss of consciousness, severe weakness, or other rapidly worsening symptoms. If severe symptoms occur at high altitude, moving to a lower altitude as quickly and safely as possible can be lifesaving.
Yes. Physical fitness does not guarantee protection against altitude sickness. The speed of ascent and individual susceptibility are important factors.
Stop ascending and rest. If symptoms are mild, allow time for acclimatization. If symptoms worsen, become severe, or fail to improve, descend to a lower altitude and seek medical attention.
Mild altitude sickness is usually temporary, but severe altitude-related illness can be life-threatening. Confusion, difficulty walking, severe breathlessness or loss of consciousness require emergency treatment.
Gradual ascent and adequate acclimatization are the most important preventive measures. People at increased risk may also discuss preventive medicines with a healthcare professional before travelling.
Medical Disclaimer: This information is provided for general educational purposes and should not replace professional medical advice, diagnosis, or treatment. If you experience severe or rapidly worsening symptoms at high altitude, seek emergency medical care immediately.
