Just as you’re congratulating yourself for staying relatively healthy and fit and eating right, along comes the bad-news notification from your doctor’s office.

You have pre-diabetes.

Say what? In your recollection, you’ve passed every fasting blood sugar test with flying colors —yes, the one where you zoom to the lab early in the morning, breakfast-less.

But this test, your doctor explains, is different. It’s called the A1C or hemoglobin A1C, and it measures your typical blood sugar levels for the past three months.

Confused? You’re not alone. Senior Planet investigated.

What’s the AIC Test?

The A1C become more widespread since an international committee of experts recommended it in 2009 as a way to help diagnose both type 2 diabetes and a condition known as pre-diabetes. (In 2010, the American Diabetes Association included the A1C in its clinical practice recommendations, too.) In pre-diabetes, your blood sugar levels are higher than they should be, but not high enough for a diagnosis of full-blown diabetes.

In the past, the test was mainly used to see how those who already had diabetes were controlling their blood sugar — if their medication and lifestyle measures were working. Experts say the switch to more widespread use occurred partly because the labs doing the tests became more standardized, so their results were less likely to vary from lab to lab.

The A1C is an easier test, so doctors like to prescribe it in place of the fasting blood glucose or 2-hour oral glucose tolerance tests. “The A1C test has become preferred by many clinicians and patients because it doesn’t require fasting or a 2-hour lab visit,” says Matt Petersen of the American Diabetes Association. Also, the A1C can be done any time of day.

So, How Reliable Is the A1C?

Like other tests, the A1C is not perfect—and no, its results don’t always jibe with the results of the two other blood sugar tests.

For instance, your fasting blood glucose could come back normal, while your A1C could show you are in the pre-diabetes range — or vice versa. The A1C result can be up to half a percent higher or lower than the actual percentage, the National Institutes of Health says. And, even though the A1C is being used more, says Minisha Sood, MD, endocrinologist and director of inpatient diabetes at Lenox Hill Hospital, New York, there are pitfalls. “If you have iron deficiency, your A1C is going to be a little higher,” she says. Certain ethnicities, including those of African American, Mediterranean or Southeast Asian descent, may be more likely to have inaccurate A1C results, the NIH says.

The other two tests aren’t perfect either. And yes, the result of one type of test may be abnormal but not the other.

How Helpful Is a Pre-Diabetes Diagnosis?

Experts disagree strongly on this point. Giving someone a diagnosis of pre-diabetes, some say, creates an artificial category. Writing in the BMJ, British researchers estimated that if the numbers advocated by the American Diabetes Association were adopted worldwide, one third of the UK adult population and more than half of Chinese adults would be diagnosed with pre-diabetes.

Experts do agree that having a pre-diabetes diagnosis doesn’t automatically mean you’ll go on to develop full blown diabetes. And proponents of the pre-diabetes category say that if you’re overweight or sedentary, or eat unhealthfully, getting an abnormal A1C result may be a wake up call to shape up.

Bottom line? The point is to catch diabetes or diabetes risk early and try to reverse it or control it. Any of the tests can do that, but depending on your health and health habits, ethnicity and family history, the A1C might not be the right one for you.

• Still curious about A1C? The National Institutes of Health has more info.
• Want more info on blood sugar testing, overall? See this resource.

 Have you been diagnosed with diabetes or pre-diabetes?