Final answer:
The first sign of dehydration is feeling thirsty. Other signs include dark urine, dry mouth, fatigue, dizziness, and decreased urine output.
Step-by-step explanation:
The first sign of dehydration is usually feeling thirsty.
When the body loses more water than it takes in, it signals the brain to trigger the sensation of thirst. Thirst is the body's way of telling us that we need to drink fluids to replenish the water we've lost.
Other signs of dehydration include dark urine, dry mouth and throat, fatigue, dizziness, and decreased urine output.
Learn more about The signs of dehydration