I have learned to relax and not ask why, unless there is a repeated pattern I could perhaps do something about. It's gone, over and done with - so forget it!
It may be time Paul started "accommodating" his insulin to his food and not vice versa - diabetic life is much easier that way... especially as there are a lot of situations that will not allow you to be strict with your diet. It might do wonders for his outlook in life in general (I have been reading your other posts earlier). Try to get him to come here and do some reading.
Good luck and all the best to both you and Paul.
