What TEST actually determines IF YOU ARE DIABETIC?

What test or tests actually make the determination that you are diabetic?  Is it the fasting glucose, the A1C, both???
My fasting glucose was normal, but my A1C was 6.4 at a lab that determined that 7% was the high end of the scale.  Thank you.

[WaveRider]

The following tests are used for diagnosis:

    * A fasting glucose (FPG) test measures blood glucose in a person who has not eaten anything for at least 8 hours. This test is used to detect diabetes and pre-diabetes.
    * An oral glucose tolerance test (OGTT) measures blood glucose after a person fasts at least 8 hours and 2 hours after the person drinks a glucose-containing beverage. This test can be used to diagnose diabetes and pre-diabetes.
    * A random glucose test (RGT), also called a casual glucose test (CGT), measures blood glucose without regard to when the person being tested last ate. This test, along with an assessment of symptoms, is used to diagnose diabetes but not pre-diabetes.

Since blood glucose can fluctuate widely from day to day, the above test cannot provide a good assessment as to how well one controls their glucose. With this in mind, the doctor orders an A1C test which measures the overall effectiveness of blood glucose control over a period of time, normally the past three months.

Your test results indicate that you are normal.