What the vet said about changing the diet from a dry food diet to a wet food diet is true. Many cats who are diabetic who get switched to a totally wet food diet can become diet controlled and don't need insulin anymore. Some cats, however, like Macho and my kitty Ruby, still need insulin after the change to wet food. The supplement that the vet is selling, while it contains some good vitamins for cats, will NOT replace insulin. Please don't buy it and think it will cure Macho's because it will not. The only things that will help Macho are low carb wet food and insulin.