My beautiful dog Whisky is not feeling well

Whisky the beagle is not eating as much, drinking lots of water (way too much), and he's asking for the door very often.  I'm pretty sure he's developping Diabetes or kidney problems.  I'll have to bring him to the vets this week if he doesn't get better...as I write he's decided to eat so that's a good sign.  He's going to be 9 years old in April; he also has hip dysplasia and arthritis in his hips.  I'll have to start thinking about what's best for his quality of life soon.