HbA1C measures the amount of hemoglobin in the blood that has glucose attached to it. Hemoglobin is a protein found inside red blood cells that carries oxygen to the body. Hemoglobin cells are constantly dying and regenerating, but they have a lifespan of approximately three months.
Glucose attaches, or glycates, to hemoglobin, so the record of how much glucose is attached to your hemoglobin also lasts for about three months. If there’s too much glucose attached to the hemoglobin cells, you’ll have a high HbA1C. If the amount of glucose is normal, your HbA1C will be normal.