I agree that N often isn't the best insulin for cats, and that many cats do better on Levemir, Lantus and ProZinc. That said, some cats *do* do well on N, and it's cheaper than the others, so it may be worth a try.
Please please read and follow
the link Jen gave you, especially the part about feeding before giving the shot. I'm fairly certain that N is a test-feed-shoot insulin. That means you want to test the blood sugar levels before you give food, so that you can get a BG reading that's unaffected by food spikes. Right after that, you feed the cat and give him about an hour to start digesting the food.
This is important: if the pre-feeding BG reading was under 300, DO NOT give insulin! N is known for sharp, fast drops in BG levels, and every cat reacts differently to each different insulin. It may be completely safe to give your cat N at numbers less than 300, but you can't be certain of that until you get more data. If the pre-feeding BG level was over 300, then give the N.
You'll eventually want to run a BG curve -- getting a series of BG readings every hour from pre-shot until the BG starts rising again (usually somewhere around +5 to +7 on N). But you'll need to give Muse's body several days to adjust to getting the insulin before the data you get will be completely reliable for deciding whether to increase the dose. Until then, when you have time -- over the weekend, at night, whenever -- try to grab some random blood tests, to see where Muse's BG levels are. Document the pre-shot number, the time that you gave the shot, and any random BG test you manage to run.
Now, you'll note that I said that you won't initially get data that's reliable to decide whether to increase the dose. But you *will* get data that may indicate that you might need to decrease the dose. Until you get a feel for how Muse reacts to insulin, if you get a reading of ... let's say 70 or less, please come onto the boards and ask if you should be concerned. A 70 in itself is absolutely *nothing* to be concerned about. In fact, if that's the lowest that Muse's BG goes during the cycle, that's fine. But, if that 70 occurs too early in the cycle, when the blood sugar is still dropping, then Muse *might* be headed for a hypoglycemic event, and -- *if* intervention is necessary -- it's less stressful on you (and Muse) to start early.
I'm also suggesting 70 as a watch number because some cats can have hypo symptoms at higher-than-typical-hypo BG numbers, and because, if you come onto the boards at an odd hour or a holiday weekend or something, there can be less folks around than normal. If you come on at +5 and say you got a reading of 70, you'll almost certainly be told to test again in half an hour and post that number -- but at least people will have time to see your first post and know that there might be a problem coming up, and folks will stick around to help.
If you do need to post for help in this situation, please post on the main Diabetes Health board; that probably gets more traffic than the N/Vetsulin forum. And please use a informative header like "2u Humulin N, +5 = 70 -- am I okay?" That'll get faster looks from knowledgable folks than a less descriptive header like "not sure if this is right".
Finally, has your vet told you how much insulin to give Muse, and how frequently? I know that Muse is now stabilised enough to come home, but please *please* check back in here with the dosage before you give her insulin. Most cats are stressed when they're at the vet's, so their BG levels will tend to be high when they're being 'stabilised' in an unfamiliar environment. When they come home, they relax and their BG levels decrease. So a dose that was perfectly safe at the vet's may be too high a dose to continue on at home.
And sometimes vets treat cats with diabetes like small dogs with diabetes, and cats and dogs react very differently to insulin. Some vets will start you at just one shot a day, and the metabolism of a cat is simply too fast; almost every cat needs shots twice a day. And some vets will start you at 2 or more units. Because some cats can be very sensitive to insulin, it's usually much safer to start at a lower dose of just one unit twice a day and give that time to settle in before increasing the dose. The exception to this is if the cat has proven to be prone to ketones / diabetic ketoacidosis (DKA), in which case you need to be careful in reducing the dose. So please, if you would, just check back in here and let us know how many units you're supposed to give Muse, and how frequently?
FWIW, ReliOn is WalMart's brand name for their medical products; you can get ReliOn syringes, glucometers, test strips, etc. I used to be a fan of their .3cc 31-gauge short insulin syringes, but the last couple boxes I got from them were by a different supplier and the needles were less sharp than they used to be. Not sure if I'd've continued getting them or switched to a different brand, like BD.
Good luck to you and to Muse!! --
Jean and her Gwyn