If you are testing the urine for diabetes, then you would need to get it tested that day as storing it could give you a false result. If he is diagnosed with diabetes mellitus then the first priority would be to get him stabilised. This usually means keeping him in the vets for a day for them to do a glucose curve - this is where they take blood samples frequently during the day to test the glucose levels and administer insulin, work out when the insulin peaks etc. You would then have to be very strict re feeding regimes, exercise etc as any change in that could mean that the insulin won't work as efficiently. There are other problems that can occur as a result of the diabetes such as liver problems, eye problems such as cataracts etc. The main problem of course would be if you couldn't get the dog stabilised. We have quite a few diabetic patients and some have been so for a good few years and are still going strong so its not a death sentence but there will be a few animals who may not respond to insulin treatment. There is another kind of diabetes called diabetes insipidus and this is what my old boy Brook had. The first symptoms I noticed were peeing during the night (although I'm not sure he was aware of it as it was on my bed
), insatiable thirst and then it progressed to not being able to control his bladder during the day as well as he used to. The way to diagnose that is a water deprivation test and again it involves a day trip to the vets. Treatment comes in the form of eye drops (v v expensive & wasn't practica in our case) or tablets called hydrobendroflluazide (I think!!) which were nice and cheap from the chemist. I noticed an almost immediate improvement once we started on the tablets thankfully, as he was a very clean dog and would get very upset when he finally realised he was wetting indoors
If your dog is drinking a lot more than normal and the urine test doesn't indicate diabetes, then another option may be to do a blood test to make sure all his organs, ie liver & kidneys are still functioning okay
Good luck and hope you get to the bottom of it