Professionals - About A1C
What is A1C?
The A1C test is also called glycated hemoglobin, HbA1c, or glycosylated hemoglobin. A1C provides an indication of your patient’s average blood glucose control for the past 2-3 months. Hemoglobin is part of the red blood cells and binds to glucose. The A1C complex is formed when the glucose in the blood binds irreversibly (glycates) to hemoglobin. The higher the glucose level in the blood, the more that binds to the hemoglobin. Therefore, A1C values are proportional to the amount of glucose in the blood. The A1C result is in percentage (%) units and reflects the percentage of the hemoglobin that is glycated.
Hemoglobin remains glycated for the lifespan of the red blood cell, about 90-120 days. Therefore, the A1C test reflects an average blood glucose control for the past 2-3 months. Mean blood glucose of the 30 days prior to the A1C test contributes to 50% of the A1C value. Fasting plasma glucose contributes more to A1C results in patients with poorly controlled diabetes. In satisfactory to good control of diabetes, postprandial glucose is the predominant contributor.
- American Diabetes Website, http://www.diabetes.org/type-1-diabetes/a1c-test.jsp.
- Calisti L, Tognetti, S. "Measure of Glycosylated Hemoglobin", Acta Biomed, (2005); 76, suppl 3: pp. 59-62.
- Woerle, HJ, Neumann, C, Zachau, S, Tenner S, Irsigler, A, Schirra, J, Gerich, JE, Goke, B. "Impact of Fasting and Postprandial Glycemia on Overall Glycemic Control in Type 2 Diabetes. Importance of Postprandial Glycemia to Achieve Target HbA1C Levels.", Diabetes Research and Clinical Practice, 77 (2007); pp 280-285.
- Monnier, L, Colette C. "Contributions of Fasting and Postprandial Glucose To Hemoglobin A1C" Endocrine Practice Vol 12 (Suppl 1) Jan/Feb 2006; pp 42-46.