Well, I always found that I was very sensitive to the lantus, maybe because I took a low dose. My normal bedtime dose was 10.5 - I actually had to try to eyeball a half unit in my syringe because 10 would make me high in the morning and 11 would make me low! That is the same as the basal I use for my pump - set currently at 10.4 units a day.
However, if I had a day of higher than normal exercise, I would cut my dose it 9.5 so as not to go low overnight and the next day. Even these small adjustments could mean the difference in being high or low the next day.
So I guess we are all different!
Julie