You can but it will play havoc with your cat's BG numbers. Getting a cat whose ketones are elevated to eat can be a challenge. Ketones develop if there's not enough insulin, not enough calories, and often because there's an infection or inflammation present. In other words, the food is important. Getting fluid (water) into your cat is also important -- it helps to dilute the ketones.
If the vet thinks it's fine to manage this at home (and you may need to learn how to give subcutaneous fluids), make sure you discuss a plan if the situation worsens. It's a holiday coming up. You want to be sure you know that to do/where to go if Peter isn't back to himself or if you're seeing that the ketones are still a problem. Ketone levels can change quickly and always at an inconvenient time. I'd encourage you to have a plan that hopefully you will not need.
