When we have a physical exam, the physician will typically include a measure of glucose (sugar) level in the bloodwork report. 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, the prevalence of diabetes in the U.S. is estimated to be 37 million; with a prevalence of type 2 diabetes that is 10-20 times that of type 1 diabetes. Additionally, there are an estimated 96 million Americans with prediabetes. Both prediabetes and type 2 diabetes are more likely to occur in older adults who are physically inactive and overweight, although either condition can occur at any age. Diabetes and prediabetes significantly increase the risk of cardiovascular disease, 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 lead to these serious health problems.
As mentioned above, individuals 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 various components 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, individuals with prediabetes and diabetes are advised to have a blood test called hemoglobin A1C (also known as glycated hemoglobin) at least twice a year. Hemoglobin is a protein that is found inside red blood cells; its’ function 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 3 months. This in turn gives the physician and the patient a much better idea than a snapshot of how well (or not so well) the condition is being controlled. Here is 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 3 months was about 154 mg/dL. As a point of reference, an average hemoglobin A1C in someone who does not have prediabetes or diabetes is about 4.5%. This equates to an average blood glucose level of about 83 mg/dL over the past 3 months. Table 1 below provides a comparison between hemoglobin A1C levels and average blood glucose levels. People with diabetes are advised to keep their A1C level <7% by controlling their weight, making dietary changes, becoming more physically active, managing stress, and by taking medication such as insulin or an oral diabetes medication.
Several years ago, 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 again if the first reading is elevated. Prediabetes is 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 in advance to include the hemoglobin A1C level in your bloodwork. This test is becoming more mainstream; but it may be a while before it becomes a routine part of a physical examination for middle-aged and older adults as well as others who are at risk for developing prediabetes or diabetes.
Knowledge is power; but putting that knowledge into action is the key for preventing or managing disease. Knowing your blood cholesterol, triglyceride, glucose and waist circumference values, as well as your resting blood pressure numbers is a great start. It is also very beneficial for you to know your hemoglobin A1C number!
Table 1. Comparison of Hemoglobin A1C Test Result and Average Blood Glucose Level over the Past 3 Months.
American Diabetes Association (www.diabetes.org)