Welcome to the world of FD…it’s not easy, but cats can live normal lives with correct care.
If you have not already, sign up for the Feline Diabetes Message Board. The members there are awesome; they talked me down from the proverbial ledge on more than one occasion!
One thing that stands out from your OP: Humulin is NOT a good insulin for cats. (It once was considered ok, but that is from older studies. The most up-to-date studies do not recommend it and many vets will no longer prescribe it. Some vets, however, are not up-to-date in their research on FD and still use the older protocols and often learn very little about it in vet school, according to mi vet, they glossed over it in one seminar.) It is very fast acting and wears off too quickly…it doesn’t last 12 hours in cats, so their cycle is a series of sugar spikes and drops. It WILL bring the numbers down quickly, but they don’t usually stabilize there for long. Sometimes it can cause too fast an too big a drop, and you do not want to deal with hypoglycemia as it can very quickly be fatal without much warning. The more recent protocols, and the ones that have by far the best remission rates call for using a long-acting insulin, either Lantus or Levemir. The cycle is much gentler, with a slow drop for about six hours and then a slow rise. Definitely Google the Roomp/Rand protocol and bring it to your vet; if begun very soon after diagnosis it has over an 80% remission rate. It does involve at-home testing, but tests done at home will produce more accurate numbers anyway as stress can cause glucose to go way up or way down, depending on the cat. I would talk to your vet about switiching to a more appropriate insulin ASAP.
My cat is on Lantus and, while I don’t think he will go into remission (diagnosed too late, as vet misread test results; long story…), his numbers are very, very good all the time…I just checked his average for the last 30 days and it’s 98-well within the normal range for a cat on a human meter.
Feeding has made a HUGE difference for my FD cat. Dry diabetic foods are all too high in carbs, low-carb canned food is what will help. You will want to keep a hypo kit available at all times-gravy canned food, like Fancy Feast gravy lovers, is often enough to do the trick if you catch a drop in glucose soon enough as gravy is high in carbs. If you have a dangerous hypo, you will want Karo syrup, which can be rubbed on the gums if the cat can’t swallow, or can be given rectally.
I agree that the 12-hour feeding schedule is silly. Think of human diabetics…they are specifically instructed to eat many small meals and snack through the day as you want the levels to stay steady, not spike up and down. Generally, when the cat is on an appropriate insulin, you can feed throughout the first six hours after the shot as the insulin is doing its job. You don’t want to feet within two hours before a shot as it can artificially inflate the numbers. My cat eats six times a day.
It is a LOT to deal with at first. It will get better, though! Do check out FDMB and the Roomp/Rand studies (and share those with your vet!). Once you get into a routine of caring for your cat, it gets easier…the hardest part for me is that I can rarely go anywhere in the evening or overnight as the 12-hour insulin schedule is strict.
(actually 4 to be exact) I curve several cats per day on a 24 hour hourly schedule. Many of the cats are on Lantus (and yes, some GP vets do prescribe it once a day). For most cats, it works quite well and some do go into remission. However, Humulin N is an insulin that really does get cats back on track with hard to challenge new diabetes, and unregulated ones (ie. ones that arent well regulated on Lantus). Im not disagreeing that lantus isnt good…it is, for a stable diabetic it really is the best one out there and I have had my own cat on it with remission! But, there is a time and place for Humulin N. Maybe not for the OP’s cat, but for you to come and say “tell you vet to switch the insulin” is maybe a little premature without knowing the curve.