Hello,
I am sorry to see you are having problems with your dog. As you have recognised diabetes may be a possibility, but there are other diseases that can cause similar signs. It is important that you make an appointment with your vet so that they can examine your dog and identify the cause of the problems so that appropriate treatemnt can be instituted.
It would be most helpful to your vet if you were able to take with you to the consultation a record of exactly how much water your dog is drinking. So measure how much water you add to the bowl each time and how much is left at the end of the day. Also collect a urine sample into a clean pot on the morning of the appointment. This should be relatively easy to do with a male dog (the vet will only need a few teaspoonsful). From this sample they will be able to give you a pretty good idea immediately as to whether your dog has diabetes or not.
I wish you well
Katharine
Dog Veterinarian
I have been qualified for 20 years and have additional quals in small animal medicine/imaging