Hi Joji! I can give you one person's opinion about some of the prescription foods not being up to snuff and why vets still suggest them. Honestly, like most people doctors, most vets are not nutritionists. It's understandable, they have so much to learn about so many different species. I think it must be much harder to be a vet than a doctor because of this. Because they have little training on nutrition and how it effect the body and disease, too often they may rely on what they are told by the prescription pet food companies. And these companies are still producing old-fashioned products that have not changed as we've learned more about nutrition and it's effects on disease. Those companies are also in the business of making money, and they can certainly make more money if they sell food with tons of fillers.
Our Billy used to have big troubles with crystals. We did our research online, and found that many vets recommend a wet food diet to avoid them. One online vet we followed specifically said she's rather see these cats being fed the cheapest of canned cat food rather than any dry. And it makes sense. Humans with bladder stone issues are told to seriously up their water intake to help. Since are kitties are notoriously bad drinkers, eating wet food really increases their water intake. A wet food diet should both help Kitaibelia's diabetes and her bladder crystal issues. I would avoid too many fishy flavors, and watch the phosphorous level of the foods. The lower the phosphorous the better.
It can be hard to go against a vet's advice. My sweetie took our Billy to the vet when he was diagnosed, as I could not go with him. He came home with a bag of Hill's dry prescription food. I took one look at the ingredients and said I am not feeding my cat this crap. Seriously, that food is made of grains. Brian argued with me for a hot minute. We love our vet and are used to trusting him, but like I said, he's not a nutritionist. Then we did some research online, found this site, and the rest is history. Our Billy is heading right into remission. Now, every cat is different, but a good insulin like ProZic or Lantus combined with a low carb, wet food diet, will give your cat the best chance at remission. Yes, it can be hard to go against a vet's instructions, but ultimately it's you who is in charge of your cat's treatment. If you are home testing and show the vet the results, it could turn into a teaching moment. If the vet gives you too much grief, it could be time to find a new vet.
You are right to be cautious about not making changes before you start home testing. A change to a lower carb diet can majorly drop blood glucose levels. It's imperative to be home testing while you adjust the diet. While home testing is not difficult, it does take a little time and practice for you and your cat to get into a routine. You don't even have to get a pet meter that uses expensive testing strips. Most members here use people meters and it works fine. I use a cheap meter from WalMart, ReliOn, and the strips are very inexpensive.
There's a thread here on the board you should start with--
New? How You Can Help Us Help You!
There's also a ton of informative Links here, including tips on home testing.
In the beginning, all of this can be very overwhelming. We've been there. We understand. You are in here, learning all the things and asking questions to help your furbaby. You're going to be awesome!