How much water loss is safe?

A safe level of water loss for the human body is generally considered to be about 1-2% of body weight, which can lead to mild dehydration. Loss beyond 3-4% can result in more severe symptoms, while a loss of 10% or more can be life-threatening. It's important to stay adequately hydrated, especially during exercise or in hot environments. Individual needs may vary based on factors like age, health, and activity level.