blood blucose was 92 mg/dL this morning, and he wasn't even fasting: he ate 4 hours before. Urine glucose it's zero
Did you test the blood glucose level at home yourself?
The excessive drinking may be a side effect from the Onsior. Here's the product info for the tablets: https://assets.ctfassets.net/kvimhx...70e69/Onsior_Tablets_for_Cats_PI_Oct_2016.pdf On page 3 it says that a change in drinking or urination can be a side effect and to immediately stop giving the product and call the vet.