A1c refers to glycosylated hemoglobin, a type of hemoglobin that has glucose molecules attached. It can be directly measured through a blood test, and its significance is that it measures long-term control of blood glucose levels.
The A1c serves only to measure long-term glucose levels. It does not give information for glucose levels at any given isolated moment. You must still test your capillary glucose on a daily basis, even if your A1c level is low. The American Diabetes Association standard is to check the A1c level at least twice yearly.
Formation of A1c
The normal life span of a red blood cell is 120 days. During this time, glucose molecules in the blood gradually attach themselves to the hemoglobin molecules located on the red blood cell. This forms a hemoglobin A1c molecule.
Use in Diabetes
The formation of glycosylated hemoglobin does not reverse itself. A red blood cell will retain its glycosylated hemoglobin for the duration of its 120-day lifespan. Therefore, the greater the amount of glucose present in the blood over the past 120 days, the higher the concentration of glycosylated hemoglobin will be. When the hemoglobin A1c test is done, it gives information on a patient's blood glucose control over this period of time. The American Diabetes Association recommends that the hemoglobin A1c be under 7 percent.