Why Am I SO Dehydrated in in the morning? I drink plenty of water in the evening, and even a few sips right before bed, and I keep a bottle of water in bed to sip if I get thirsty at night, yet on many occasions, I wake up terrribly thirsty! I get up to pee...drink a glass of water, then will wake up again 20 minutes later to hafta pee again....yet Im STILL dehydrated... this doesnt stop until I wake up.