How do i know if i'm dehydrated?

Thirsty.: In a person of your age with an intact thirst mechanism more than mild dehydration always leads to sensation of thirst. Secondarily you can see decreased saliva and dryness of mucous membranes, constipation and decreased urine output. Lastly serious dehydration decreases skin turgor and allows a pinch of skin to remain "tented.".

Several things: Dry mouth low volume of urine dark concentrated urine. Sunken eyes.

Your oral: mucosa get dry, turgor and tonus of the skin decreases, color of the urine become dark yellow.