My Morgan was over 19 pounds and his sugar level was over 300 also. He went on insulin shots though. We started at 8 units once a day. Then I think it was 5 twice a day. Progressively we worked our way down unit by unit. He was put on Purina DM also. I've only given him the dry food though. He would get a small teaspoon of canned food, usually Nine Lives Tuna Select because it is very low in carbs with his insulin injection. I am so not a needle person either. But after a time or two, it wasn't a big deal for me or for him. Of course he just wanted the wet food. He would come and tell me when it was time for the insulin. Anyway, the diet worked and he hasn't had to have insulin for 2 years. I just keep strict watch on what he eats. The last time he was at the vet's office, they said he had lost a pound, which was a good thing. Although I am skeptical because they weighed him on a different scale. Everytime they've used this one scale all my animals have lost weight. But whatever. Morgan had been strictly rationed Science Diet Light catfood for years and would gain weight everytime he went in for a checkup. The DM is the only food that he hasn't gained weight while eating. Anyway, the point of my post was to say that I've been where you are plus with insulin injections and it is possible to have diet control the diabetes. My vet doesn't worry if the sugar level is in the mid 100s. He says that the stress of being at the vet causes the sugar levels to be a little on the high side anyway and as long as I don't notice him drinking or urinating excessively not to worry. Feel free to ask any questions you can think of though.