He won't wear a collar and I can't afford to buy an automated feeder that uses a microchip in a collar. The problem I have with leaving food out all day is that he will eat all day. He is not hungry then when I need to give him his shot. The other two cats in the house eat very little canned food so I could probably get a cheap timed feeder somewhere.
Lisa,
Tigger was on Vetsulin, and his insulin needs would vary sometimes. Vetsulin will drop your kitty's BG pretty quickly, as it's a faster acting insulin, instead of an extended release insulin like Lantus or Levemir. With Tigger, I would also leave his cat food out so he could eat when needed, just because the Vetsulin would drop him pretty quick sometimes. I also found -- for him -- that sometimes it would start to fade off around the 10-11 hr mark, instead of the full 12 hours. Also, Tigger was prescribed 3U, at shot time, but that was actually too much for him. He had a couple of hypos back to back, and then he was bouncing, so I did not give insulin that night, and we started fresh the next day with 2U, and I would adjust after that, based on his numbers. Every cat is different, however, so it might work better for your kitty than mine. I wanted to change him to Lantus or Levemir, which, based on my research on the boards here, seem to be gentler and longer lasting than Vetsulin. We didn't get to do that before he passed away, but if I were to ever have another diabetic cat, that is the way I would go, unless it just didn't make sense for some reason.
Also, we set Tigger up a XXXL dog crate as a cat condo for him, complete with kitty bed, food and water dishes, and a litter box for night time. However, that might be an idea for you while you work, so he could have his own food in there and you wouldn't have to worry about the other kitties eating it before he could. Just a thought.