Always thirsty??

Maribel • . <3
I'm always always always thirsty!! I can drink a big glass of water and be thirsty right after i drink it. I sometimes wake up in the middle of the night & go get something to drink because my mouth is so dry!! Same when I wake up the next morning.. I chug a bottle of water & its like the thirst never goes away. What could this be ? & is it serious? Opinions please!!