Okay, test, feed, wait a 1/2 hr to shoot because food needs to on board. He can eat whatever he wants until he reaches his nadir....U...he starts at the top of the U, curves down to the bottom, insulin stops working, goes back up to the top of the U. These insulins, be it N, L, U (discontinued L and U ) curved. You would do a curve to get a handle on how low they go at peak before insulin wears out and they start rising back up. Any food given after peak, the insulin is no longer working to keep their numbers from going back up. Say a cat reaches peak/nadir at +7. Any food given after +7 the insulin is wearing out and no longer helping to keep the numbers down. Look at the link I posted to Becki on what a normal curve looks like and how food affects the numbers.
Each cat can be different on this insulin as to how long before nadir, some at only +4, and then they start rising again. Fast to bring them down but no duration to keep them down for very long before going back up. Add food to that and they go up even faster.
Hope came to me on IDEXX PZI. Baby(GA) was on U for 5 1/2 years, L just didn't do it for her. Mishka was on U for several years before being discontinued and now is on PZI. I can feed them just fine but if I feed them after their nadir.....insulin worn out and numbers go climbing. The cats do adapt and become accustomed to the feeding schedule.