I wouldn't say that 7.9 was necessarily indicative of diabetes if it was a reading taken shortly after a meal or something particularly high in sugar. Lots of perfectly healthy people's levels spike for a short while depending on what they have eaten but would drop back down closer to 5.5 mmols or so quickly enough. Also, all kinds of other factors from stress to infection can increase a normal person's blood sugar. One reading on its own tells us nothing really (unless it was really high or really low). That said, it's good your doctor is cautious. I you are diabetic, or even pre-diabetic, the sooner you know the better. A test after fasting is probably the best next step...ask your doctor about it. Hope it all goes well.