If your dog is drinking lots of water all of a sudden and urinating more often, do not withhold water from your dog. If you do, you may put your dog at risk for life-threatening dehydration. According to the American Kennel Club, signs of dehydration include seeking water, excessive tiredness, dry or tacky gums, loss of skin elasticity and mucousy saliva. Instead, allow your dog to drink, and call your vet.