Blood Sugar Averaging

by | Aug 31, 2021 | Nutrition

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There is a test for average blood glucose over a period of time, because glucose tends to get stuck to certain molecules in your red blood cells (those molecules are called hemoglobin, and their job is to carry oxygen).

When you get a fasting blood glucose* test, it tells you the glucose level in your blood at one moment in time—the moment when your blood was drawn. This can be very useful information, because if your blood glucose is high, or low, it could indicate a situation in your body or your diet that you’d want to do something about.

But what your blood glucose level does NOT tell you is the average level of glucose in your blood over several months, which is also very useful information. If your fasting blood glucose level is normal but your average blood glucose is high, or low, that could indicate that some part of your body’s glucose control system is not working as it should be.

Fortunately, there is a test for average blood glucose over a period of time, because glucose tends to get stuck to certain molecules in your red blood cells (those molecules are called hemoglobin, and their job is to carry oxygen). Once stuck in a red blood cell, glucose stays there until that cell dies. Red blood cells on average live for three months, so if you measure the amount of glucose that is stuck to hemoglobin molecules you can get a pretty good idea of your average blood glucose levels for the past three months.1

The kind of hemoglobin that glucose gets stuck to is called “A1.” An A1 hemoglobin molecule to which glucose has been attached is then called an “A1C” molecule. Hence this test is called a hemoglobin A1C test.

If your doctor doesn’t ask for an A1C test next time you get your fasting blood sugar tested, you might want to request it. Tracking your A1C over time can help you monitor the effectiveness of the operation of your body’s glucose regulation system. Then you can take steps to improve the operation of that system if needed. 

Which is not to say that A1C is the ultimate blood glucose test. What it won’t tell you is whether or not you’re experiencing rapid blood sugar rises and falls, so-called “spikes.” Such spikes can in turn stimulate high levels of insulin, and that’s probably something you want to avoid. To test for blood sugar spikes, you can use an inexpensive device that instantly measures sugar in a drop of blood, called a glucometer, or get a prescription for a relatively new device called a continuous glucose monitor.

*Glucose is the name of the type of sugar that your body uses for fuel, also called blood sugar. A fasting blood glucose test is a measure of the amount of glucose in your blood when you haven’t eaten for several hours.

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.

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