More detail and supporting information is in the body of this article. 1  A1C is an abbreviation for glycated hemoglobin, which forms when glucose attaches to a protein in red blood cells. 2  As blood glucose levels rise, so does the percentage of glycated hemoglobin, so A1C is used to measure diabetes control.ore detail and supporting information is in the body of this article. 1  A1C is an abbreviation for glycated hemoglobin, which forms when glucose attaches to a protein in red blood cells. 2  As blood glucose levels rise, so does the percentage of glycated hemoglobin, so A1C is used to measure diabetes control.