Breath!
This is a mangeable condition, just as it is in humans.
To help you monitor your cat, until you get the knack of blood testing, daily assessment of the 5 Ps is encouraged.
Each day, note if you have observed the following 5 categories
Purring
Preening (grooming)
Playing
Peeing - as you make progress, the amount of wet litter may decrease. Optionally, if you get glucotest strips, those change color if there is glucose in the urine which means the glucose in the blood is too high.
Poohing - as you switch to a low carb, canned diet, the volume of feces may reduce ... and smell less, too!
Note how much water you put down each day - measure what you put down, measure what is left, and figure the difference is due to drinking, plus some evaporation. This too, should reduce a bit as canned food has more moisture, and controlled diabetics don't need to drink gallons of water.
Uncontrolled diabetic cats are ravenous. If you measure how much you put down and how much is left, plus note if the cat is begging for more food (which you may give, in moderation), this also gives clues to the diabetic management status. For additional notes on obesity and calorie requirements in cats, please see
Cat Info