It's the "vice versa" that happened to me recently. For quite some time, a couple of weeks or even a month, my sugars were running high, no matter what I seemed to do. I tried tinkering with my dose a little (but not too much, because I was really afraid I was crashing at night without knowing it). Nothing seemed to help -- I would wake up high every morning, and sometimes struggled with highs during the day, too.
I thought it might have something to do with the fact that I felt like I was getting sick, but my body successfully fought that off, or at least so I thought, and my sugars were still running high. I tried increasing my basal rate to no avail. I decreased it to check my suspicions that I was crashing during the night.
And then, about a week ago, my blood sugar readings were suddenly coming up fairly normal again. I hadn't made any changes to my dose, hadn't dramatically changed anything else that I could think of (stress levels, amount of exercise, etc.). Just one day, I woke up and my blood sugar was normal, and I've had only a few random highs in the week since.
So what changed? Perhaps it took my body longer to fight off that illness than I realized. Perhaps there was some other change that I wasn't aware of. Whatever the case, though, I'm glad to be back to "normal"!