What is AMS? HSJ Heli 1 min read AMS (Acute Mountain Sickness) is the mildest and most common form of altitude sickness, causing headache, nausea, and fatigue above approximately 2,500m. It is usually managed with rest and avoiding further ascent. Share: Twitter Facebook WhatsApp ← Previous article What is HACE? Next article → Which regions does HSJ Heli & Assistance cover for emergency rescue?