The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


November is National Diabetes Month: you know your ABC’s; do you know your A1C?

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Live well

Thursday, Nov 05, 2015

When we have a physical exam that includes blood work, our health care provider typically tests our blood glucose level. A normal fasting blood glucose level is between 70-99 mg/dL.  Individuals with fasting glucose levels between 100-125 mg/dL on two separate occasions have prediabetes, while individuals with fasting glucose levels >125 mg/dL on two separate occasions have diabetes.

According to the American Diabetes Association, there are 29 million Americans with diabetes. There are two major forms of diabetes, type 1 and type 2. The prevalence of type 2 diabetes is 10-20 times that of type 1 diabetes. Additionally, there are an estimated 90 million Americans with prediabetes! Both prediabetes and type 2 diabetes are more likely to occur in middle-aged and older adults who are sedentary and overweight, although they can both occur at any age. Diabetes and prediabetes significantly increase the risk of cardiovascular disease (the leading cause of death in the U.S.), nerve and capillary damage, as well as damage to the retina of the eye. You may be wondering exactly what it is about diabetes that would cause these serious health problems.

As mentioned, people with prediabetes and diabetes have higher than normal levels of blood glucose. When blood glucose levels remain elevated over an extended period of time, some of the glucose molecules become permanently attached to areas such as nerves, capillaries, and hemoglobin. This attachment process is called glycation, and is undesirable because it can cause damage to these vital body components.

Because a fasting blood glucose test only provides a snapshot of glucose values at one specific point in time, people with prediabetes and diabetes are strongly advised to have a special blood test called hemoglobin A1C at least twice a year. Hemoglobin is a protein that is found inside red blood cells. Its job is to carry oxygen. Some of the glucose in your blood can penetrate red blood cells and attach to hemoglobin.  The hemoglobin A1C test measures what percentage of hemoglobin molecules are glycated, and provides an excellent measure of average blood glucose levels over the past 2-3 months. This in turn gives the physician a much better idea than a snapshot of how well (or not so well) the patient has been controlling their condition. Here’s an example: If the hemoglobin A1C test comes back with a result of 7%, it means that the patient’s average blood glucose level over the past 2-3 months was 154 mg/dL. As a point of reference, an average hemoglobin A1C in someone who does not have prediabetes or diabetes is about 5%. This equates to an average blood glucose level of 97 mg/dL over the past 2-3 months. Table 1 provides a comparison between hemoglobin A1C levels and average blood glucose levels over the past 2-3 months. People with diabetes are advised to keep their A1C level <7% by controlling their weight, making dietary changes, being more physically active, managing stress, and by taking medication such as insulin and/or an oral diabetes pill.

Recently, the American Diabetes Association ( approved the use of the hemoglobin A1C test for diagnosing prediabetes and diabetes. The advantage of this method is that it doesn’t require fasting beforehand, so it’s a lot more convenient than having a fasting blood glucose test performed on two separate occasions if the first reading is elevated. Prediabetes is now diagnosed when the hemoglobin A1C is between 5.7-6.4%, while diabetes is diagnosed when the value is >6.5%.  So, the next time you are due for a physical exam, you should ask your physician if it would be possible to measure your hemoglobin A1C level if he/she was not planning to do so. This test is becoming more mainstream, but it might be a couple of more years before it becomes a routine part of a physical examination for middle-aged and older adults as well as other individuals.

Knowledge is power; but putting that knowledge into action is the key for preventing disease. Knowing your blood cholesterol, triglyceride and glucose values, as well as your resting blood pressure is a great start. It is also very beneficial for you to know your hemoglobin A1C number.  Put this on your ‘to-do’ list the next time you have a physical exam.

Table 1. Comparison of Hemoglobin A1C Test Result and Average Blood Glucose Level over the Past 2-3 Months.

Hemoglobin A1C Result Average Blood Glucose Level over the Past 2-3 Months
5% 97 mg/dL
5.5% 111 mg/dL
6% 126 mg/dL
6.5% 140 mg/dL
7% 154 mg/dL
7.5% 169 mg/dL
8% 183 mg/dL
8.5% 197 mg/dL
9% 212 mg/dL
9.5% 226 mg/dL
10% 240 mg/dL

Learn more about physical activity, healthy eating, weight loss, and disease prevention by taking our Nutrition for Health and Fitness, Weight Loss Strategies, and/or Personal Training Education workshops. You need not be a health and fitness professional to attend; everyone is welcome!