Mauer is looking so much better on levemir. So glad you switched.
Which canned food Sasha? If you can find the manufacturers website for a particular brand and the specific flavor, that lists the minimum and maximums for protein, fat, fiber, moisture (water), ash, you can use this simple carb calculator to find a rough estimate of the carb content of any canned food.
http://www.scheyderweb.com/cats/catfood.html
Before you do that calculation though, you may want to see if the canned food is on this list
UK Cat Food List
In case that link doesn't work, here is the URL.
https://docs.google.com/spreadsheets/d/1J5JpMe6TDXrHq_aTl9hUtHy6Gs9oRBqlz4nPGKxtySA/pubhtml