Well you do remember that Lantus needs to build up the shed first right? So the first few doses on any dose aren't going to show immediate results until that shed is full and that in the beginning can that 3-5 days to establish. For now lets leave him at the 1u unless he tells us otherwise.
Now since I'm the one that has started all mine after I adopted them on insulin, I start all mine at .5u bid and work up, just a personal preference, as I'm also learning the cat. But the rule of thumb with the SLGS protocol is if the cat has already been changed over to a low carb canned diet, then you start at .5 if they are still on dry then 1u is the starting dose. Tight Regulation will calculate based on ideal weight the starting dose.
Mel and The Fur Gang