I am also "prediabetic". My fasting blood sugars were in tthe so-called 'normal' range, when tested, but my post prandial readings are too high for a non-diabetic.
Last year I went though three months if bronchitis which I could not fight off, on top of which I developed a throat infection and then a few weeks after came down with a cold, at the same time I had developed a secondary bronchial infection. I felt so bizarre at times, as if I had been poisoned. Knowing what I know now, it was probably raised BG. Due to having a 'normal' fasting result, my (pre)diabetes was missed. The inability to fight off infection is a characteristic of diabetes, and I'd never known anything like it.
This week I will be seeing the GP to make some progress on arranging further tests, but in the meantime I am testing at home. I have been at 9.6 2+ hours post prandial, and I dread to think what it must have been at 1 hour. Doesn't bear thinking about. Tonight my levels haven't come down from post prandial more than 0.5 since eating 5 hours ago.
If you haven't done your own readings yet, you may find it an eye opener. Or a shock!
I also believe stress plays a role. I have no obvious risk factors, although I have ME and I am physically unable to exercise, but my BP is good and I'm not overweight, I don't have a sugar habit, I rarely drink—but I have been living with long term stress because of the place where I live and having my sleep disturbed every night and morning. My neighbour who lives with similar problems also developed diabetes a few years back and she says stress was the tipping point for her.
I'm glad you're getting your (pre)diabetes investigated. I am having to be more proactive. I went through so many investigations, but the answer was right there, but masked by a 'normal' FBG even though I'd had a fairly high pinprick test from an out of hours doctor.