ME! I have had hypoglycemia my entire life. I was FINALLY diagnosed with CFRD last September. My OGTT test, and A1C is still normal, but they put me on a dexcom continuous meter for one week and saw that I was hitting 200 and 300 with all food.
The dietician I am working with (she works at my CF clinic, and my endocrinologist's office) seems to be the most knowledgeble person I've ever met about CFRD, and she said "if you're going low, you're definitely going high".
I don't know if that is true for everyone, but it turned out true for me. I was undiagnosed for many, many years.
I'm still having trouble treating my highs, because I still get a lot of lows. My pancreas is slow to react (thus the highs), but when it does put out insulin, it really over does it (thus the lows).