Someone with more experience than I have will be along soon to give you more specific advice. I am still really new to this.
Sharing my cat's story:
My cat was diagnosed in late September with a Bg in the 500s I believe. He weighed 20.3 pounds and was down from about 27 pounds at last year's annual exam. He was given Lantus and was started at 3 units twice a day, then moved to 4 units twice a day. In between I changed from dry c/d to dry m/d (suggested by vet) then found out that i should not be giving any dry food at all so I moved to canned m/d. Once the diet was better for Bo and his shed was filled with insulin from the shots, he had a seizure. The vet wanted him to stay on 4 units but give only once a day. The vet also said to expect at least one more seizure. i could not give that much knowing that he had had a seizure. AND I did not like the statement about expecting more seizures. Apparently his plan was to rapidly regulate by pushing the dose up until a seizure and then decrease some. If you have not already printed out the sheet about hypos, do that immediately and get some karo syrup and a liquid medicine dispenser to keep handy. Bo had a seizure at night when we were asleep. Thankfully, he was in the bed with us so i knew when it happened. I had to give him some karo syrup and then I followed up with some high CARB gravy food and took him directly to the emergency vet. I was so grateful to have that knowledge about the hypos from this board. Bo had NO symptoms prior that evening and just went straight into the seizure around 11 pm.
All that to say, I got some excellent advice from the people on this board. They said that he should have been started on a lower dose so that regulation could happen better and only increased (or decreased) small amounts at a time. Apparently Lantus is a very good type of insulin for cats. With the diet change, a little more exercise, and a good insulin for him, he got off the juice after about a month and is still off. I think his last shot was the middle of October. His BG levels now remain in the 40 - 80 range every time I check him with the Relion meter. He looks good, feels good, and has a lot more energy. Although the Lantus was a good call and the move to high protein diet was right (although he did not know that canned was a lot better than dry for Bo), I was not sure about the other things the vet was telling me. He did not like me testing either. I just did not feel right so I did more of what the people on this message board suggested and now Bo is off the juice. I have him now on Fancy Feast classic (and do not give him any fish cat food at all due to previous experience with urinary problems with my Himalayan). He and his brother and sisters like it and it is high in protein. He still weighs more than he should at 19.2-19.6, he is a large cat at almost two feet long and two feet tall not counting his tail.
Personally, I would take your cat off the w/d and put him on the classic Fancy Feast ( we use the Chicken Feast, Turkey and Giblets and Liver and Chicken and he gets one can in the morning and one can in the afternoon). I had my cats on w/d before and they GAINED weight so the move to high protein FF may be a good one. I think that once Kitty's insulin gets regulated or his body begins to kick in its own, you will see that he is not as famished. All of mine acted like they were starving when i had to ration their food until I got them on canned high protein. After a short time of eating better food, they actually leave some food in the dishes for later. While Bo was on his shots, I did give him a "snack" of his left over breakfast and dinner portions of food in the middle of the day and in the middle of the night. I think that 4 small meals a day was a plus in his body beginning to make its own insulin. He is back to eating twice a day now since he is not taking shots and is doing well.
Also I would change to Lantus. Test before EVERY shot and if it is 200 or below, I would not give a shot. You have to also go with your gut on making decisions. Stay on a rigid routine of 12 hour intervals for shots. Stay low on the dosage and only do small changes. (there is a recommendation on BG levels and whether to give shots, and on increasing or decreasing dosages based on BG somewhere in this information on the board. I know someone will direct you to that if you have not seen it already. Wish I had it to attach.) I believe it said that if the BG was under 150, do not give a shot and if it was between 150 and 200, you may decide to test again later OR give a smaller dose. Lantus is a longer lasting insulin and hopefully will see some positive changes for Kitty soon. Good luck.