Acute Mountain Sickness
Acute mountain sickness (AMS), also known as altitude illness, is a common condition above 2400 metres (8000 ft). It is especially common if you have not had a chance to acclimatize by ascending gradually. The prevalence of AMS varies between 15% and 75%, depending on your speed of ascent, altitude gained, sleeping altitude, and individual susceptibility. Acute mountain sickness can progress to high altitude cerebral edema (HACE) or be associated with high altitude pulmonary edema (HAPE). Your ascent should include rest days. If possible, increasing your sleeping altitude by more than 300-450 metres (1000-1500 feet) each night, should be avoided.
Symptoms of AMS include mild to moderate headache, loss of appetite, nausea, fatigue, dizziness and insomnia. Mild AMS usually resolves with rest plus medication for headache and nausea.
You should not continue to ascend (especially to a higher altitude) if you have any persistent symptoms of altitude illness. If symptoms worsen and there is no improvement you should descend (at least 500 metres/1600 feet) to a lower altitude.
More severe AMS (increasing headache, vomiting, increasing fatigue or lethargy) may indicate onset of high-altitude cerebral edema (HACE) - recognized by confusion, difficulty with balance and co-ordination, staggering gait. Start treatment with medication and descend immediately. Increasing dry cough and breathlessness at rest may indicate high altitude pulmonary edema (HAPE). Descent combined with medication (and oxygen, if available) is the best treatment for more severe AMS, HACE, or HAPE. Consider evacuation if necessary.
The use of medications may be helpful for preventing and treating altitude sickness. It is best to consult a physician prior to your departure for a high-altitude trip (climb).
Risk of Acute Mountain Sickness is present in the following countries:
