I failed the one hour several times, but only had GD once. I followed strict orders about carbs/food before the test. I wasn't a heavy carb eater anyway, due to the fact that I had GD before, but I still failed the one hour. Now, they just make me do the three hour right away, so I don't have to waste my time doing two tests.
I did. I ate a peanut butter sandwich before the test. Duh. Failed it and had to do the 4 hour test and passed that one!