The morning fasting test is very unreliable, and therefore rarely used by doctors for a diagnosis without further tests. So much can affect these fasting tests, such as stress, activity, restless night's sleep etc. Just getting up, getting ready, dashing to the surgery for the test, and feeling stressed about it all can raise this level.
The HbA1c test is different as it measures a sort of average of your blood glucose over the previous 2 to 3 months.
There is also another test available, the oral glucose tolerance test, which measures your post meal insulin reaction.
Some experts believe all 3 tests should be performed before a diagnosis is given.
If you are really concerned, go back to your doctor and ask for further tests.