Hi Donva, and welcome --
I completely agree with the others that you should start home-testing your cat's blood sugar levels. You can find some helpful videos and information on that
here.
Also, I have some reading for you to do. First off, you really need to read
Melissa and Popcorn's post on hypoglycemia, it's symptoms and treatment. And you'll also want to read
Jojo and Bunny's post on stocking your hypo toolkit.
Also, a caveat on the following: I am not, nor ever have been, a Lantus user. So if you get different feedback from actual Lantus users, please give more credence to what they say.
Regarding your vet and the way your cat is responding to his insulin: several of the older insulins have been discontinued in recent years, and new insulins are taking their place. Lantus is definitely one of the insulins that folks here on the board have been having good experiences with, but it sounds to me as if your vet is administering and measuring Lantus as if it was one of the other insulins s/he probably has lots of experience with. Unfortunately, Lantus does really work in quite the same way as other insulins.
Please head over to the
Lantus forum. You'll want to read several of the stickies at the top of the forum. "New to the Group - Please read" gives you the basic organisation of the board, terminology, info on syringes, curves -- lots of really good introductory stuff. The sticky on "Proper Handling and Storage" gives you information on the different ways Lantus can be dispensed and how to best handle it to preserve its efficacy; reading the stuff in that thread will help save you money, and you may want to share it with your vet so they'll know the info and options for their other clients. And the sticky labelled "Insulin Depot AKA Storage Shed" is a guide (in layman's terms) of how Lantus works differently from other insulins. You'll definitely want to review that, and I'd strongly recommend that you print it out for your vet as well so they'll be able to adjust their processes for any other diabetic cats on Lantus that may come their way.
Also, until your cat is regulated on insulin (or, even better, off insulin entirely!), I'd suggest checking periodically for
ketones. Ketones are a not-common but still possible side effect of unregulated / under-regulated diabetes, and they may indicate the start of diabetic ketoacidosis (DKA). Low levels of ketones may be treatable at home, and high levels of ketones may require hospitalisation at a 24-hour care facility for several days, so (if they occur at all) it's better to catch them when they're low.
To test for ketones, please stop by the diabetes aisle of your local pharmacy and pick up some ketostix (I've always found them in the aisle, but some folks report that their pharmacy keeps them behind the counter). Ketostix are little plastic strips that you stick in fresh urine; if ketones are present, the strip changes color.
Some other folks will be by and you'll get more encouragement to home-test blood sugar levels, and also encouragement to switch to a low-carb diet. *Please* do *NOT* switch to a low-carb diet until you're home-testing BG levels and almost certainly switching to a lower dose of insulin. Your cat's already experiencing hypoglycemia and switching to a low-carb diet without lowering insulin and home-testing could be ... well, Very Not Good. You *do* want to switch diets, but not quite yet, okay?
In the meantime, read up. You'll undoubtedly have a bunch of questions; please feel free to ask. We've all been where you are and we know what you're goine through -- and we're here to help you and your cat. Welcome --
Jean and her Gwyn