Hi Sue,
Blood glucose levels in a non-diabetic should be in the 4-7 mmol/l range, but the full range can be from as low as 3.5 to as high as around 8.
But ten is not good. Tens don't happen to non-diabetics. Just no. Go to your doctor again, or better yet, go to another doctor who's actually bothered to diagnose you for something as serious as diabetes.
And although I said ten is not good, it could be a lot worse. When I was diagnosed with type 1 diabetes as a six-year-old (18 now), I was past the honeymoon phase. When I went into hospital first, I was 30 mmol/l.
Deal with it soon, knowing it can be dealt with. Best wishes for the future,
Isobel.