What time is he scheduled to start?
The reason I ask - I want to double check they're considering the typical Lantus pattern and accounting for when nadir might be...I would hate for that to be while he's under.
Will they check his BG during?
Unfortunately I'm seeing this a little too late, I probably would have moved the shot up an hour (or the full two) tonight depending on BGs...just perhaps done a reduced dose.
Truthfully I can't say what to do in the morning. While I wouldn't want to skip, a lot depends on what he does tonight and where he's at with shot time tomorrow. Remember you still have a full 3.5U depot sitting there, so a one-time dose of 1.75U might not make much of a dent. He's had nice numbers, and who knows how much the dental will help things.
I have thoughts on what I would do, but hoping Wendy comes by as she's better to advise. I'll check later and if not, I'll give you my thoughts so you at least have something to consider.
*And remember, no food does not necessarily mean no insulin. So even if he doesn't want to eat tomorrow night, you may not have to skip (again depends on BG, what shape he's in, etc)