Retrospective #66: Fasting Glucose Best Predictor of Diabetes Risk (NOT!)

The 2012 headline in Diabetes in Control, a website for medical professionals, declared, “Fasting Glucose Best Predictor of Diabetes Risk.” That is patently false! Okay, it’s true, this was seven years ago, but using a fasting blood glucose as a diagnostic tool for incipient (“new-onset”) Type 2 diabetes is an artifact of the last century. Really!

The report in Diabetes in Control was based on a presentation at the European Society of Cardiology/World Congress of Cardiology in 2011. This report was targeted to clinicians with a misleading and patently wrong headline.  It reminds me of another report I had just read that eggs were nearly as bad for you as cigarettes. I have read so many authoritative dismissals of that report that I am embarrassed for the Canadian researchers who produced it. Shame on them for this “science,” and the journalists and editors who published and promoted it.

The reason for writing this column is to tell you that YOUR FASTING BLOOD GLUCOSE (FBG) IS NOT THE BEST PREDICTOR OF DIABETES RISK. Anyone who is informed in this field knows that. Just for the record, though, the diagnosis of Type 2 USED TO BE two consecutive FBG tests at or above 140mg/dl (lowered ≥ 126mg/dl in 1997).

Sometime in the early 2000’s the hemoglobin (Hg) A1c test replaced the FBG test.  The A1c test is inexpensive and measures the average serum glucose from markers on red blood cells over their two to three-month life cycle.

The best diagnostic tool for Type 2 diabetes, however, is the Oral Glucose Tolerance Test (OGTT).  It is a relatively expensive and time-consuming test because it takes from 2 to 4 hours to administer. In my case, it was ordered in a hospital out-patient setting in 1992 by an endocrinologist. That was also the year he ordered my first A1c test.

You may also have had an A1c test at a recent checkup. The normal range of 4.0 to 4.9.  If your doctor tested yours, he or she probably suspected it was above normal. Most practitioners, like the Low Carb Dietitian’s – see Retrospective #65 below – will not be “too concerned” if your A1c is rising but not yet approaching 6.5%. You’ll be told, “We’ll watch it” and “Lose weight.” YOU SHOULD BE concerned, though, as heart attack risk doubles as A1c rises from 5.5% to 6.5%, the threshold for a Type 2 diagnosis. The Pre-diabetes A1c range is ≥5.7% but <6.5%.

There is a much easier way, however, to find out if you have Impaired Glucose Tolerance (IGT). You can measure it yourself with a glucometer (meter, test strips and a drop of blood). Purchase one in a pharmacy and test before eating and one-hour and two-hours after. That’s how the “Low Carb Dietitian,” discovered she was Pre-Diabetic.

If your blood sugar rises above 140ml/dl 1 hour after eating, or does not drop back to “normal” (in the low 80s) after 2 hours, you are developing Insulin Resistance and are becoming Carbohydrate Intolerant. In other words, YOU ARE PRE-DIABETIC (or DIABETIC) and YOU NEED TO CHANGE YOUR DIET to minimize your intake of carbs to regulate your glucose metabolism and control your blood glucose. If your blood “sugar” (glucose) surges above 140, you need to get a prescription for more strips and test at home regularly to learn how to “eat to the meter.”

So, if your doctor is still doing a Fasting Blood Glucose (FBG), or even an A1c with the advice to “Lose Weight” and “We’ll have to watch it,” you either need to find a new doctor or TAKE CHARGE YOURSELF and find out what foods spike your blood sugar so that you can avoid them. You know that they are mostly simple sugars, starches and refined carbohydrates, but the meter will help you discover your level of carbohydrate intolerance. Pre-diabetes and Type 2 diabetes need to be recognized and diagnosed early and, when it is, they are reversible BY DIET ALONE. The way our bodies react to what we eat tells us we have a problem. And the best and least expensive way to find that out for yourself is to test your own blood sugar right before eating and again one and two hours after a meal.

As the Diabetes in Control headline that is the title of this column indicates, most of the medical community is still hopelessly out of date and behind the times. The solution: TAKE CHARGE of your own health, before it’s too late.