Welcome Theresa and Blaze. I'm glad you found FDMB and hopefully we can help answer your questions about his diet, how much he needs to eat, and how much he is willing to eat at a time. Fancy Feast Classics and Friskies pates are all below 10% carb content, Hill's W/D is 25% carbs (
Food Chart from
www.catinfo.com) and is too high for a sugar cat.
Dr. Pierson from the catinfo website recommends " start with protein minimum of 40, fat maximum of 50, carb max of 10, and for cats with kidney issues....phos less than 300."
It's important to note, that changing from a higher carb food to a low carb food can significantly lower the BG, and you should be testing before doing so to prevent any hypoglycemic events. Especially in view of that 134 BG you got at the vet.
Most of us feed more frequent small meals to our diabetic cats, as unregulated diabetics can't utilize the food as well, and they are very hungry. With Lantus you do not have to have an entire meal on board before injecting because it does not cause a fast blood sugar drop.
Lantus is not dosed on a sliding scale, it works better used consistently, and depending on the lowest BG of the cycle between shots, then adjustment can be made by 0.25 U. Dosage is not based on pre-shot numbers.
It will be helpful for you to visit the Lantus forum
HERE and read the yellow tagged stickies at the top of the page. This information will help you understand how Lantus works, as it's a depot insulin and works differently than the older insulins that have been used for dogs and cats. Many vets still provide instructions that would apply more to the older "in & out" insulins, particularly dosing and food requirements. It's so hard for our vets to address all the different pet types/breeds/issues that come to them, and keep up with all the new information too.
I'm sorry that you think home testing is not going to be something you will be able to do, and there may be some members that can also help with that. It's going to be very difficult for you to tell if it's safe to inject the insulin each time, as well as determine how well it's working for him. I am going to search out some information I remember reading from one of our members that was finally able to test a feral cat that didn't tolerate any human touch when he was diagnosed. I will be looking for that information and get it to you ASAP.
Ok, I found that in Djamila's signature, it's interesting reading
https://docs.google.com/document/d/1HXYL4-YAz6-yWNxEoqlRkp4aqJaAT6X_qYQ1ypgQpHw/edit
We do have some members that use the paw for testing and here is one YouTube video showing that. How to check your cat's blood sugar from their paw