Welcome to the best place you never wanted to be, but will be so blessed to have found!
A few things you might want to be aware of before heading back to the vet's in a couple of days.
There are 3 keys to managing diabetes in cats.
1) Insulin. Hopefully your vet will be fairly up to date on diabetic cat care and will prescribe either Lantus, Levermir or Prozinc, all 3 of these are long lasting gentle insulin that work very well in cats. Also hopefully they will start you on a low dose, we recommend no more than .5u-1u given twice a day. Cats need insulin every 12 hours because they have such a high metabolism rate. Try to avoid being started on NPH/Humulin N...this is a harsh insulin in cats but works well for dogs. It just doesn't last long enough in a cat's body and causes steep drops and rises.
2) Diet- This is something you can start while waiting to see the vet in a couple of days. We recommend a low carb/high protein diet. You don't need the prescription foods either, there are no "special prescription items in them" and they are expensive compared to those of the same quality or better quality foods available on the commercial market. Popular brands around here on the less expensive side are Friskies Pate, Fancy Feast Classics, or even Walmart's Special Kitty. On the more pricey high quality end would be Wellness, Evo, or Merrick. All of which are canned foods..Almost all dry food is too high in carbs for a diabetic kitty. And if you happen to have a multicat household like I have here, you can switch everyone over to the same diet as your diabetic. The best thing I ever did for my 11 non-diabetic kitties was to adopt two diabetics..The diet switch has greatly improved the health of all of my cats.
3) And this is the biggie....Learning to test at home. This is absolutely your best tool in not only keeping your best friend safe while on insulin but it will also keep a lot of cash in your wallet. You do not need the fancy animal only meter, any human meter that takes a small sample of blood will work just fine. Wal-mart has an excellent little meter called Relion Micro or Confirm that runs about $9 and the strips are about $30 for 100 strips (strips are the most expensive part). We simply prick the edge of our cat's ear much like a human diabetic pricks their finger. The advantages of testing at home is that you will first know if your buddy is high enough to give insulin to safely, second get truer numbers because they won't be influenced by vet stress, and third you won't have to keep dragging your kitty to the vet all the time for curves, because you can do them at home and then share those numbers with your vet.
Lastly remember that the only stupid question here is the one that goes unasked. Everyone that will respond to you either has had or currently have a diabetic cat that they are successfully treating at home....A few of us even have multiple diabetic cats.
Mel, Maxwell, Musette & The Fur Gang