Hi Tim and Zim, welcome to FDMB. I'm glad you have found the board and will have the benefit of a wealth of information and the support of the community.
It is best to feed a sugar cat more frequent smaller meals throughout the day, unregulated diabetic cats are usually very hungry because they can't utilize food well. You could use a timed feeder or freeze wet food in ice cube trays and leave out cubes for meals in the day or night. Now having 3 other kitties around might lead to some issues there, but hopefully we can put heads together and work toward a good solution for everybody concerned.
Since you are brand new here, please create a signature so that Zim's information is available when you post. It saves repeated asking and answering down the road.
Setting up your signature (light grey text under a post). Here's how:
click on your name in the upper right corner of this page
click on "signature" in the menu that drops down
type the following in the box that opens: kitty's name/age/date of diabetes diagnosis/insulin you're using and dosage amount /glucose meter you're using/what he eats/any other meds or health issues he has. You can add your name, and a geographic location (sometimes the time zone matters) Be sure to SAVE when you are finished.
You don't mention if you are testing his blood sugar at home, and if you aren't, I encourage you to do this. Just like with humans, it's a very important component of diabetic treatment. If you test before an injection you can be sure it's safe to "shoot", and testing at other times in the 12 hour cycle will tell you how low the insulin is taking the blood sugar. This is important to determine if the dose is too much, too little or a good dose. It also will help you prevent a hypoglycemic event
(very low blood sugar) which can be life threatening. It also saves trips to the vet for testing, avoids that "vet stress" for the cat, which can significantly raise the BG, and keeps a few more dollars in your pocket. We can help you choose supplies and learn the process.
Another reason for testing since you are transitioning to the all wet diet: this also lowers the blood sugar (BG) and the insulin dose may need to be adjusted accordingly. We changed Idjit's diet, was not advised to test before injections, and to test only a couple of times a week, midday. Just happened to test on the right day and he was going too low. The members here helped me intervene and prevent a hypo. Made a believer out of me!
Regarding the 12/12 schedule, yes, it is important. You want consistency with timing and dosage. By the way, a dose is not determined by the pre-shot numbers, but by the nadir, or lowest BG level in the cycle. Many new members see a high number in the morning and think more insulin is needed, and begin adjusting the dosage. The only way to see if the dose is right is to test, record the insulin and testing data on the spreadsheet we use here and see what the pattern is. If the vet did a one time BG test for diagnosis, the prescribed dose might have been influenced by the stress of traveling to, and being at the vet, and be too high.
You can read about Lantus and the protocols used here on the Lantus insulin support forum:
http://www.felinediabetes.com/FDMB/forums/lantus-basaglar-glargine-and-levemir-detemir.9/
There are many knowledgeable and experienced members that can answer your questions about using this insulin in this forum.