I have an almost identical story but I adopted my cat from Longmont Humane who ended up being diabetic. It's a good thing they didn't find the diabetes in Henry (or my Hobbes) because they would likely have put them down. So it's a blessing in disguise IMHO.

Anyhoo.....I have to give Hobbes insulin twice daily too. I've been doing it for the past 7 years since I adopted him. The biggest thing to remember is to take Henry in for his fructosamine tests once the vet decides his insulin levels are set properly (it took us around three weeks to get to the optimal insulin dosage). We take Hobbes in once every 6 weeks or so for the fructosamine test - it gives an average of the blood glucose levels so they can tell if the insulin dosage is right. There's no doubt you will have to adjust it at some point.

Keep a tube of cake frosting (or some other high sugar thing) on hand in case you need it in an emergency (Henry may need a strong dose of sugar at some point if his glucose level hits a ditch).

Dogs who are diabetic will always be insulin-dependent according to my vet. And since the problem tends to advance in dogs, his insulin needs may likely increase. That's why regular testing is important. I don't advocate doing the daily ear prick for blood test because my vet told me it was unnecessary as glucose levels don't generally tend to change that much between the fructosamine tests where the ear prick test is worthwhile.

Diet Diet Diet...and exercise. We make sure Hobbes gets a regulated diet every day. We feed him the same amount and always feed him when we give him his insulin. They have to eat if they're going to get their insulin. If they don't eat, I think that's when they go into insulin shock. Our Hobbes is a good eater so I put down his food and give him his shot while he's eating. He never even flinches because he's focussed on his food. You have to keep their general health even keel too. That's why the exercise is important.

Hobbes has lived the last 7 years with no major issues except that we got lazy about his fructosamine tests. During that time his insulin requirements dropped dramatically so it turned out that we were giving him nearly three times the dosage he needed. As it turns out, cats (unlike dogs) can actually recover from diabetes and even totally get off of insulin at some point (though you have to still maintain their diet). So again, the regular fructosamine (or maybe your vet prefers glucosamine) tests are very important to make sure Henry is getting what he needs.

I'm glad you've decided to take care of Henry even though he has diabetes. Not everybody would do that because it's a lifetime commitment and it isn't cheap (between the insulin, syringes and tests). That reminds me.....we get our syringes from 1800PetMeds.com. They're quite a bit cheaper than we could get through our vet.

OK, I've rambled on but hope I've helped some. If you have any other questions, I'd be happy to try and help if I can.