Smithy 8.5 seems a tad high for random test but I need to know the full context to make a better judgement. i.e. when had you last eaten and what had you eaten type thing.
The GD test itself is very unreliable and shows alot of false positives IMO providing unecessary stress and angst to a lot of pregnant women. You would get a much more accurate diagnosis if you were able to do home blood glucose monitoring (finger stick tests) say four times a day 2 hours after meals and one fasting one first thing in the morning. if you did this for a week you would have a much more acurate picture of whether GD is likely. A one off random glucose like you did could happen to anyone diabetic or not.

Hope that makes sense....also a level of about 5 would be an expected fasting level not after food.