The word normal means “conforming to a standard; usual, typical, or expected.”
In the US there are three widely accepted tests and standards for determining normal blood sugar: 1) the blood glucose level after several hours of not eating, referred to as fasting blood glucose level, 2) blood glucose level over 2 hours following consumption of a standardized amount of glucose (Oral Glucose Tolerance Test), and 3) the percentage of glucose that has become attached to hemoglobin (Hg) in the blood over a period of time, referred to as HgA1C, or often just “A1C”.
In practice, the Oral Glucose Tolerance Test is very rarely performed, so we will ignore it here. Here are “normal” values for the other two tests:
|Fasting Plasma Glucose (FPG)
|less than 100
|100 to 125
|126 or higher
|less than 5.7%
|5.7% to 6.4%
|6.5% or higher
A diagnosis of normal, prediabetic, or diabetic would be made by a doctor based on one or more of these tests. In this case, however, “normal” doesn’t necessarily mean healthy.
Why not? Because such a diagnosis does not take into account the change in glucose levels that might be occurring either in the short term or the long term, and it’s that change that is most indicative of the effectiveness of the body’s energy management system.
In the short term, over a period of a few hours, your body generally responds to the consumption of foods high in glucose (such as sucrose and refined carbohydrates) with insulin that causes excess glucose to be stored. A crucial question is, how much insulin is required to manage your glucose levels. If that amount is increasing over time, then your body is likely developing a condition called “insulin resistance,” which increases your risk for prediabetes and diabetes as well as other chronic diseases.
In the long term, if your blood sugar levels are gradually rising year over year from the low 80s to the high 90s, that also is an indication of developing insulin resistance, which would not be diagnosed medically because your glucose is still in “normal” range.
The question we should be asking, then, is not whether our blood sugar levels are “normal,” but whether they are “optimal”—that is, do they indicate that our body’s energy management system is functioning as it should be. We’ll take up exactly what would be meant by optimal blood sugar levels in a future Insight.