Hi,
In June 2009 the American Diabetes Association announced at their scientific sessions in New Orleans that a group of diabetes experts had determined that using the hemoglobin A1C test was a reliable and more convenient way to diagnose diabetes. The members of this expert panel decided that an A1C cut-point of 6.5% or higher would be used to establish a diagnosis of diabetes. They also recommended that the diagnosis be confirmed with a repeat A1C test unless the person had clinical signs or symptoms of diabetes overall glucose levels over 200 mg/dl. they also suggested that people with an A1C in the range of 6 to less than 6.5% are at higher risk of developing diabetes (also called glucose intolerant or pre-diabetes in some sources). These individuals should be targeted for lifestyle modifications to prevent or delay the development of diabetes.
The committee also said A1c values are more stable after collection compared with the other tests. Blood glucose levels in samples taken from nondiabetic patients have been known to decrease by 3-10 mg/dl in as little as one to four hours when kept at room temperature. While that may seem like a small decrease, it is enough to move someone out of the diagnostic category of having diabetes if their blood glucoses are borderline, causing individuals and their health care providers to have a false sense of security. Hemoglobin A1C values vary less than fasting plasma glucose, or FPG, levels, and the measurement of an A1c has technical advantages compared with fasting glucose testing. These include the ability to test without regard to fasting state, to test immediately when in the office rather than requiring the patient to travel to the lab on another day, and the stability of the A1C test within the test tube versus that loss of glucose over a few hours time.
On a personal level, I find that many individuals test at times of the day during which they may get their best readings, such as in the fasting state. As others point out, your "worst" readings may be in the first 1-2 hours after eating a meal, rather than in the fasting state when you first arise for your day. So if a person misses seeing those points where there glucose is high, they might think that things are ok. This was the reason for the development of a number called the estimated average glucose, or eAG. This calculation turns your A1C into a number you are familiar with, such as you might see on your meter. The eAG for an A1C of 6.3% is 134 mg/dl, which is above the range of "normal" glucose. Your health care provider is being a wee bit aggressive (?) shall we say by calling you a diabetic, however he or she is probably looking at your lifetime risk of developing diabetes and assisting you now to control your risk of uncontrolled blood glucose and the complications that come with it.
I hope this is helpful, Laurie