Diabetes and the Hemoglobin A1c Test
By Roland Larrabee, MD
The hemoglobin A1c ("A-one-C") test is a blood test used in the care of people who have diabetes. The hemoglobin A1c percentage is a way of looking at your average blood sugar control over a period of 3 months.
Sugar absorbed from your digestive system circulates in the bloodstream. When the blood sugar is high, the sugar attaches to the hemoglobin protein in red blood cells, forming hemoglobin A1c. Red blood cells live 90 to 120 days. This means that once sugar has combined with the hemoglobin in red blood cells, the hemoglobin A1c stays in the blood for 90 to 120 days. This means the amount of hemoglobin A1c in your blood reflects how often and how high your blood sugar has been over the past 3 months.
Hemoglobin A1c is an excellent way to check how well you are controlling your blood sugar over a 3-month period. Hemoglobin A1c measurements are important because:
- They confirm your daily home blood sugar monitoring results.
- They help predict your risk of diabetic complications. The higher the hemoglobin A1c percentage, the greater the risk of developing diabetic eye, kidney, cardiovascular, and nervous system disease.
No preparation is necessary. One of the advantages of this test is that you do not have to fast before you take it. A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab. There are also portable machines that can determine the value from a fingerstick – these can be performed in physician offices or even in a patient’s home.
The hemoglobin A1c percentage rises as your average blood sugar level rises. For adult diabetics the results are usually judged as follows:
- less than 7%: excellent blood sugar control (some experts recommend less than 6.5%)
- less than 8%: good control
- less than 9%: fair control
- 9.1% or higher: poor control.
The hemoglobin A1c result can be converted to what would be the “average hourly blood sugar over a three month period” that would create that particular A1c result. For instance, an A1c level of 7% correlates to an average hourly blood glucose of 170, whereas an A1c level of 9% correlates to an average hourly blood glucose of 240. As you can see, the lower the A1c, the better.
If you have been diagnosed as diabetic and your test is not normal, your health care provider will talk to you about how to lower your blood sugar through diet (weight loss and eating the proper proportions of carbohydrates, protein, and fat), exercise, and/or medicine. Keeping your blood sugar levels and hemoglobin A1c levels in or near normal ranges will help you avoid the complications of diabetes, such as eye disease, kidney disease, or nerve damage.
The A1C test should be done every 3 months unless you are in good control, e.g., less than 7%. If you do have good control of your blood sugar, your provider may recommend having the test every 6 months. \
Dr. Larrabee is Associate Director of Family and Community Medicine at the Walter L. Aument Family Health Center, 317 S. Chestnut St., Quarryville.
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