Altitude sickness is the most common challenge for people trekking the Annapurna Circuit and can affect anyone, even well-prepared trekkers. Precautions are set in place, such as increasing elevation gradually, drinking enough water (you have to be hydrated all the time), balancing meals, properly dressing up, well-acclimatizing, avoiding drinking and smoking over 3000 meters, hiking higher and sleeping lower to support your acclimatization and overall enjoyment of the trek.