Oh no.
Does sound like diabetes is possible. My only advice there is to get your kitty in as soon as possible for bloodwork and urine testing. Cats can be very hard to manage when this is diagnosed. It makes it worse when ketones are present. The longer you wait, the more likely that will be the case. And you don't want to come home to him in a diabetic coma (if you think this is the case).
There might be a sticky in the Library about this, but:
Anesthetic protocol
Vaccine protocol
Charge for phone calls?
Somebody there at night? If not, what do you do if pet needs to be hospitalized?
Do they have xray on-site (digital is best)?
Lab on staff? (best to send out, but sometimes answers are needed right away).
Ultrasound there (not necessary, but is helpful).
I'm forgetting tons. Morning brain.