Frankly, I'm not convinced it is in the dog's best interest, either. I have not committed to doing this indefinitely. Hopefully I can get her blood sugars down and get her a little healthier. She fights the injections so bad; you'd think I was killing her. Other than that 15 seconds twice a day, she seems pretty happy.
Apparently Miniature Pinschers are prone to diabetes. She was VERY obese (also a risk factor) and she started losing weight, drinking a LOT of water, and urinating huge volumes every few minutes. She even wet herself in her sleep. She is 7 years old.
A dog's normal blood glucose is 60-110 (like a human). Hers was 585 the first time it was checked. They take NPH insulin (just like some humans). Rather than running back and forth to the vet, I've been using a glucometer at home and phoning in the results and we adjust her dose. It's just really hard to balance diet/exercise/insulin.
If we do decide to put her down, at least we will know we tried. I just had my 18 year old cat put to sleep two weeks ago. It's a hard thing to do, but sometimes necessary.