High Glucose Count

My cat, Whiskey, is about 9 years old, and has just been to the vet and we have been told he has a very high glucose count.
They said it's not Lukemia, but that he has to go back for more tests.
He's not eating, moving, or drinking.
He broke his pelvis when he was about a year and a bit old, which healed perfectly, and other than that he's been perfectly healthy.
Does anyone have any ideas as to what might be wrong with him?
He's not MY cat, he's my little sisters, but I love him dearly, and am very worried about him.
Any help would be appreciated.
Thankyou in advance
Nikki xxx

High glucose is usually a sign of diabetes, but prior to that the number one sign is drinking alot and peeing alot, and weight loss. Did they say how high it was? Cats can be know to have a high glucose if they are stressed out also, like a vet visit would do. Did they find the glucose in urine or blood? I would do a full blood panel to check everything (organ function, blood cell counts, glucose, etc.) and then go from there. What did they do for the kitty while he was there?

Thankyou for replying.
I'm not totally sure what they did to him at the vets as I'm away from home at the moment and my Mum took him.
But he had been peeing everywhere possible - more so than usual and not in his litter tray - I dont knowif that's of any significance.
What's the differenve between finding glucose in the blood or in the urine? Is one more serious than the other?

If a blood sugar is over about 250 then it spills over into the urine, so if the glucose was found in the urine then it is higher than 250. If the checked a blood glucose, then they would know an exact number, I am assuming it was found in the urine, and that is why they would want to do more testing (a blood panel).