What Are “Optimal” Blood Sugar Levels?

by | Jun 1, 2023 | Treatment

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If your glucose levels are “normal,” does that mean they’re “optimal”? Now there’s a way to find out.

Not long ago, we published an Insight on the subject of “normal” blood sugar, that is, the levels of glucose in your bloodstream which doctors use to diagnose conditions of pre-diabetes and diabetes. In that Insight we pointed out that while these measurements may detect the fact that your body’s management of its blood sugar levels is so poor that you have or are on track to have a serious disease, they do not detect whether you may be approaching that condition in time to avoid it—such as 10 or 20 years ahead.

How is it possible to predict diabetes so far into the future? By understanding that diabetes is actually just a very advanced stage of a condition that progresses over time. That condition is the malfunctioning of your body’s energy management system, which has as a primary function keeping your blood glucose levels within a rather narrow range. It’s actually a condition that is best described as the impaired control of glucose levels, also referred to as glucose dysregulation. 

But the description of diabetes as glucose dysregulation, although true, is incomplete. In diabetes, the glucose dysregulation occurs because the body does not produce or properly respond to the hormone insulin, which is critically important to the processing of the carbohydrates that you eat. So the full and correct definition of diabetes is this: 

Diabetes is a disease in which the body’s ability to produce or respond to the hormone insulin is impaired, resulting in abnormal processing of carbohydrates and elevated levels of glucose in the blood and urine.1 

Typical blood tests for glucose, the ones that doctors use to make a diagnosis of pre-diabetes and diabetes, are of two types: fasting glucose, which is the level of glucose in your blood at least 12 hours after your last meal, and A1C, which measures average glucose in your blood over a period of three months. But neither of these tests measure your body’s immediate response to the consumption of carbohydrates, and it’s that information that would tell you whether or not you are processing carbohydrates abnormally.

Ideally, your body’s response would be to employ insulin effectively to rapidly store the extra glucose that is generated in your blood when carbohydrates are digested, so that there is no glucose spike.

And this leads us to a description of optimal, as opposed to normal, blood sugar levels2.

First of all, optimal would refer to dynamic patterns of glucose over a period of time under a range of consumer foods. These patterns would generally remain below 140 mg/dl throughout the day without spikes into higher ranges except under high carbohydrate consumption. They would average, over a 24-hour period, about 90 mg/dl and, during periods between meals, about 80 mg/dl. 

Until recently, determining whether or not an individual’s glucose levels were optimal would have been a complex task, requiring the testing of blood many times over a period of at least 24 hours or longer. That has changed with the development and widespread availability of continuous glucose monitors (CGMs), which use a sensor attached to the body that can read blood glucose level in the skin. At the time of this writing a prescription is required to get a CGM, and many doctors require a diagnosis of diabetes to write such a prescription, but with a little internet research you can find doctors who will prescribe a CGM “for general health information and wellness purposes.”

If you want to know if your own blood sugar levels are optimal, or whether or not your body’s energy management system might need some adjustment, you might well find that the time you spend in such research is worth the investment. Many users of CGMs report that the continuous measurements allow them to immediately evaluate the effects of various foods on their blood glucose level, information which is invaluable in helping them to achieve the goal of achieving optimal levels. 

Fundamentals of Health Alliance

Fundamentals of Health Alliance


The Fundamentals of Health Alliance works to publish useful and reliable information about nutrition and health. Their mission is to empower readers to be informed with honest, non-biased information about food, nutrition and the vital components of health.


  1. See the eSavvyHealth course “The Carbohydrates Wars” for a fuller discussion and explanation of this definition.
  2. What follows is based on an excellent 2007 research paper from Germany which provides a clear picture of dynamic glucose responses: Continuous Glucose Profiles in Healthy Subjects under Everyday Life Conditions and after Different Meals  (J Diabetes Sci Technol. 2007 Sep; 1(5): 695–703.) 

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