Sheila, I wonder if he has been going that low through the last week or so...since there are very similar PM and AM PS's...maybe tha is just his cycle?
Not to make light at all, but 39 is really within reasonable limits if that is the lowest and he will get himself back up reasonably without rebound and whatnot- which is quite possible that he has been doing that as I mentioned.
Since you are home frequently, what do you think about giving this dose change some settle time and then the next time you catch a low like the 39, why not test through it to see if he hangs?
I mean, if you are testing every half hour or so and he hangs, no biggie, and if you see that it is actually a continual drop, then you are there to feed.
of course, I don't recommend this to new folks or people that don't have data or the time to be home to test theough leaving the low without food...And Sheila has her own mind to decide what she feels comfortable with.
I just wonder- with such similar PS's recently, if he might have been dipping that low for nadir, hanging, and then going back up...what do you think?