Blood loss or blood transfusions

One of the significant factors of A1C levels is the red blood cell life span. The reason for this is that the A1C test measures the percentage of your red blood cells that have glucose bound to the protein hemoglobin in your blood.

Your A1C may change as a result of changes in red blood cells. Your A1C results could be wrong if you've recently undergone a blood transfusion or lost blood. In addition, studies show that patients receiving a large number of blood transfusions (eg, hemochromatosis) will have artificially high A1C levels because the donor blood was stored in a dextrose solution. This makes the A1C unreliable for 3 months following a blood transfusion.