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Dear Diabetes: What Is A1C?

What is an A1C level?

Dear Diabetes: What is an A1C level, and what should mine be? Is it different for people living with type 1 and type 2 diabetes?

First things first: what does the A1C test actually measure? Hemoglobin is a large protein in red blood cells that helps ferry oxygen through your bloodstream. A fraction of the glucose in your bloodstream diffuses into red blood cells and attaches to hemoglobin. When hemoglobin is bound to a glucose molecule, it is called hemoglobin A1C (or HbA1c).

As you might imagine, if there is excess glucose in your bloodstream, a higher percentage of the hemoglobin gets glycated (that is, bound to glucose). Because the glycation process is slow and because red blood cells live and circulate in the bloodstream for several months, the fraction of hemoglobin that carries glucose can be used to measure how much sugar has been sitting around in your bloodstream during the previous two to three months. A person without diabetes, for example, generally has an A1C under 5.6%, meaning that less than 5.6% of the hemoglobin in his or her blood sample has glucose attached to it. A person living with diabetes may have a higher A1C percentage, indicating that the hemoglobin in their blood has had more opportunity to bind to glucose. Their blood glucose level at the time of the blood test actually may be lower than that of a person without diabetes – the power of the A1C test is that it measures the average level of blood sugar over a couple of months. (Learn more about A1C and why it’s important.)

A1C is now a recommended test for diagnosing diabetes. According to the American Diabetes Association’s 2015 Standards of Medical Care in Diabetes, an A1C value greater than or equal to 6.5% means the patient has diabetes.

Note that this A1C diagnostic threshold does not distinguish between type 1 and type 2 diabetes; all it tells the doctor is that the patient has had elevated blood glucose for the past few months. If the onset of diabetes is slow and/or atypical for type 1 diabetes, additional tests may be necessary to determine whether the elevated glucose levels are caused by insulin resistance (indicating type 2 diabetes) or autoimmunity (as would be the case with either type 1 or latent autoimmune diabetes).

Thanks to the Diabetes Control and Complications Trial (DCCT), doctors are aware that, over the long term, high A1C values are correlated with people living with diabetes developing complications. So A1C measurements should be taken several times a year, whether you are living with type 1 or type 2 diabetes. To help keep track of your A1C levels, try using this downloadable and printable chart. In general, the goal is to keep one’s A1C below 7.0%, although that varies, depending on the special needs of any given individual. As always, talk to your doctor about your specific A1C goal.

Karmel Allison was born in Southern California, diagnosed with type 1 diabetes at the age of nine, and educated at UC Berkeley. She now lives with her husband in San Diego, where she is loving the sunshine, working in computational biology at the University of California, San Diego, and learning to use the active voice when talking about her diabetes. In her spare time, Allison enjoys people, Milan Kundera, rock climbing, and the pursuit of life, liberty, and happiness. Allison is a paid contributor for The DX. All opinions contained in this article reflect those of the contributor and not of Sanofi US, its employees, agencies, or affiliates.

For more stories in the Dear Diabetes series, visit The DX archive.

© 2015 The DX: The Diabetes Experience

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