Answer: When it’s at the upper end of the normal range.
A fasting blood glucose (FBG) test is one of the most common labs I order. The normal range for FBG is 60-99 mg/dl. If this reading of blood sugar is much too high (greater than 126 mg/dl) on two separate tests, that is the definition of diabetes. The most common type of diabetes that comes on later in life is called type 2 diabetes mellitus, and is associated with obesity. That borderland of 100-125 mg/dl is called impaired fasting glucose, and indicates that a person on the way to developing diabetes.
So why all this fuss about blood sugar? The problem is that high blood sugar (and the high insulin levels that accompany it) put aging on fast-forward — putting you at much greater risk for heart disease, kidney disease, eye problems, and nerve problems. It literally takes years off your life. The complex interrelationship between high blood sugar, insulin resistance, and chronic disease has been called metabolic syndrome.
Knowing this, researchers in Israel published findings last week (1) that indicate that the problems don’t just suddently start once your FBG climbs over 100 mg/dl. Adults who had FBG of 95-99 mg/dl (still “normal”) had a fifty-three percent increased risk of cardiovascular disease compared to those with FBG of less than 80 mg/dl.
What does this mean for you? If your doctor tells you that your blood sugar test came back normal, ask for the number. If it’s over 95 mg/dl, you are at a significantly increased risk for stroke, heart attack, and coronary heart disease. Follow a healthy lifestyle, including a low-glycemic index diet and exercise, to aim for a FBG of less than 80 mg/dl.
1. Fasting Glucose Levels Within the High Normal Range Predict Cardiovascular Outcome. Am Heart J. 2012;164(1):111-116.