Acute Mountain Sickness

1 medicine

Acute mountain sickness is altitude-related illness caused by ascending too quickly to high elevation, causing headache, nausea, and fatigue. It is prevented and treated with acetazolamide.

Diamox

Acetazolamide

250mg

Diamox is a heart blood pressure medication containing Acetazolamide, available as 250mg tablets.

from $0.54 / tablet View

Key facts

  • Acute mountain sickness (AMS) happens when the body doesn't adapt quickly enough to reduced oxygen at altitude, typically above 2,500 metres.
  • Symptoms, headache, nausea, dizziness, and disturbed sleep, usually appear within hours of reaching elevation.
  • Ascending gradually and staying hydrated are the most reliable preventive measures. Acetazolamide is the established medicine for both prevention and relief, usually started one to two days before ascent.
  • Descent is the definitive treatment for severe or worsening AMS; confusion, an unsteady walk, or a persistent dry cough at altitude warrant immediate descent and medical assessment.

What causes it

Acute mountain sickness sets in when the body hasn't had time to adjust to the lower oxygen levels found at high elevation. It typically appears above 2,500 metres and comes on within hours of reaching that height, most often in people who ascend quickly rather than gradually. Fitness level offers little protection: even well-conditioned athletes get AMS if they climb too fast, while a slow, staged ascent protects people of any fitness level.

Prevention and treatment at altitude

Ascending gradually, no more than 300 to 500 metres of sleeping-elevation gain per day above 3,000 metres, is the most reliable preventive measure. Staying well hydrated and avoiding alcohol in the first 24-48 hours also helps.

Acetazolamide is the established medicine for both preventing and relieving AMS. It works by stimulating faster, deeper breathing, which raises blood oxygen levels, and is usually started one to two days before ascent.

Descent remains the definitive treatment for any severe or worsening AMS.

When to see a doctor

Confusion, an inability to walk in a straight line, or a persistent dry cough at altitude warrant immediate descent and medical assessment, since these can signal the more serious conditions of high-altitude cerebral or pulmonary oedema.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.