Insulin made a big difference for my diabetic cat. She had great quality of life for a couple years after she started getting it. She was I think 12 when she was diagnosed, and lived about 2 years after that. The daily injections didn't bother her a bit, and she really loved the prescription food too. She was her same old sweet and cuddly happy self. Do ask your vet about insulin overdose and be prepared in case it happens. One morning after her normal dose, she started acting strange - lethargic, weak, and kept hiding behind my desk. That hiding behavior is what cats do when they're looking for a place to die. We called the vet and she said said her blood sugar was probably way too low, and we needed to rub some Karo syrup on her gums. We didn't have any on hand but fortunately we have a grocery store close by, and my wife used molasses until I got back with the Karo. We took her in for blood work the following day, and the vet ended up lowering her dosage.