Let's start with the easy one. Lantus doesn't kick in or onset, for a coupe hours after the shot. So you have a bit of time to get food into him. As long as he eats a bit of food and you think he will eat more later, you are good to give the shot at the usual time.
No difference, they all have the same issues with your schedule. Basaglar is a cheaper glargine biosimilar to Lantus, the action is exactly the same as Lantus. Levemir onsets and nadirs typically a couple hours later than Lantus, but similar types of action. There are a couple differences between the glargine insulins (Lantus, Basaglar, generic) and Levemir that might be important for your situation. First, Lememir onsets a little later than Lantus, typically around 4 hours after the shot. That is both good and bad. With later onset you have a bit more time to get food in them before the insulin action start to happen, should your cat be fussy. The down side is that it's harder to see what the following cycle will look like. We generally suggest a +2 or before bed test with Lantus, to give you an idea if he's dropping fast in that cycle, meaning you have to test more or leave higher carb food out for him to be safe. With Levemir, and a later onset, that could mean staying up even later to get that test that tells you it's going to be an active cycle. The upside to later action with Levemir is that often you get get lower numbers or nadirs closer to preshot so you can tell if it was a good cycle. Levemir personally worked better for me, as several days a week I was up at PM+9 for a workout, and testing then was a really good time to tell how my kitty was doing on a particular dose. But, each persons situation is unique.
No. Shooting at 8:45PM means it's 75 minutes earlier when you shoot at 7:30AM the following day. Ideally you'd like the time to be 30 minutes or less, so at 8:15 or later. So that leaves you 45 minutes earlier than is best. Shooting that much earlier can act a bit like an increase in dose. Once he gets to a dose that gets him regulated, those 45 minutes might make him go lower than you want him to. Again, this is something you'd have to experiment with. Not all cats are as sensitive to time changes.
As for life happening (traffic, etc.), sometimes you just have to skip a shot. As long as he's not ketone prone, that's OK. The same could happen not on a Wednesday, and as long as you are within that 1/2 hour window, you should be OK. Once you miss a shot for any reason, you are OK to give it anytime as long as it's at least 12 hours (or 11.5 hrs) later than the previous one. The nice thing about the depot style insulins is that there will still be some Lantus in the system that would help tide him over some skips.
he is currently getting 4u.
