What is the first sign of dehydration? increased thirst increased dizziness decreased urine decreased endurance

increased thirst

Explanation:

Water is the main requirement of the body, the water lubricates the eyes and joints, keeps the skin healthy and hydrated, aids in digestion and flushes out waste from the body. Dehydration occurs when the body loses more water or fluid content than the body takes. When the normal water content of the body gets reduced the balance of mineral will get affected. The normal water metabolism is affected in dehydration.  

Increased thirst is the first warning sign of dehydration followed by dry mouth, tiredness, having dark colored urine and decrease urination than normal.