Highs and lows happen regularly. Sometimes a carb count is off, or the insulin isn't at peak performance due to too much heat or cold -- that last cause happened once. Boy, was that a pain.
Blood sugar also naturally trails a bit high while the insulin is working away in the body, as the insulin needs time to convert the carbs.
Sometimes you can get an entire day in range, but it's tricky. I think that I'm also nearing the end of the honeymoon stage... that'll make things trickier.
Anyway, I'm fine. As long as my blood sugar doesn't go too high for too long -- and I try to keep that from happening -- I shouldn't have to deal with any complications. I like all of my limbs....