I was lucky enough to have a very thoughtful and caring vet who pointed me in the direction of this message board after learning his diagnosis. After reading the FAQ and a few posts, I am feeling overwhelmed and not even sure if I should start on treatment or if it's in my Loki's best interest to put him down. Loki (12 years) has never been a very social cat. He doesn't like attention from strangers and for the most part, just wants to be left alone. He'd often claw at guests in the house and need to be removed. That being said, My relationship with him has been long and rewarding and It would break my heart if I lost him. I mention Loki's disposition to people because about two years or so ago, he started developing mood swing that were more violent than usual. They got so bad that my partner was reluctant to be in the house alone with the cat as it would attack randomly and unprovoked. We of course took him into the vet who said that he was perfectly healthy and that his issues were mental rather than physical. he suggested an antidepressant. We tried to keep it up, first with the pills, then with a liquid version - both were unsuccessful, as he became anxious and fearful of pill time and eventually food time, and seemed miserable all the time. After about three months of this, We decided we couldn't continue the regiment. It wasn't the quality of life that he deserved to have and the medication wasn't a solution. We expected to make a vet visit in the near future to have him put down, but in the coming days and then weeks, we noticed no violent episodes and his behaviour eventually improved to the point where I would say, it was better than it ever used to be. We couldn't believe it and thanked our lucky stars that it turned out this way. About a month ago I started observing more frequent urination, and also some strange meowing while he was eating. I brought him to the vet who took a look at his mouth to reveal some teeth that need to be pulled. In preparation she did a blood test to see if there was anything else we should be concerned with and to our shock and dismay, Loki's results showed that he was diabetic. Our vet advised us that we could treat the condition with insulin which would need to be administered every 12 hours. In addition, we'd have to test him on a regular basis. After we got home from the vet, Loki vomited for about 2 days largely in part to the stressful experience of kennelling to go to the vet and the 40 minutes travel time to get to the veterinary clinic. After two days, he seems to be back to his happy self, and we've started on his wet diet, which he's adjusting to well. We haven't started the insulin treatments yet and I'm scared that we'll have the same experience as we did trying to medicate him for his violent outbursts. My fear with giving him the insulin injections and required tests is that he will go back to being lethargic and scared of any sort of human interaction. The last thing I want is for him to be living in fear again. What is the humane thing to do here? Is it possible that diet alone could do the trick? I'm worried that my only solution is euthanasia. Has anyone had a similar experience?