Looking at the numbers for today, the nadir is at 8 hours. Does that mean that 4u is too much?
No. A +8 nadir doesn't mean "too much" insulin. Nadirs aren't set in stone. They can happen early or late in a cycle, and don't indicate a dose is too high or too low.
Also, look at the numbers from +5 to +8: 233, 229, 228, 214. Meters aren't "that" accurate. They can be off by as much as 20% (that's close enough for the FDA). If you consider "meter variance", all 4 of those tests can be considered to be just about the same number.
Good observation from Robin! The numbers looked much better when you were feeding 9-Lives. Did your vet suggest DM? It's not a terrible food, but ingredients-wise, it's no better (worse in some cases) than 9-Lives, Friskees, Fancy Feast, Special Kitty, or any other food you can buy off the shelf for a lot less money). Prescription diets like Purina's and Hill's are overpriced, and overrated. Why vets buy into the sales pitch from the manufacturers is a mystery to all of us.
As long as the food is low-carb canned, any brand will do, but if you were doing well on 9-Lives, I think I'd go back to what seemed to be working.
Carl