Symptoms. Thirst isn't always a reliable early indicator of the body's need for water. Many people, particularly older adults, don't feel thirsty until they're already dehydrated. That's why it's important to increase water intake during hot weather or when you're ill. The signs and symptoms of dehydration also may differ by age. Infant or.

Dehydration defined The body is in a state of dehydration when fluid levels drop to a point at which organs and bodily functions, such as circulation and respiration, can’t function normally..