Glucose and Hemoglobin A1c

Glucose, a monosaccharide, is the primary source of energy for the human body. It is used by the liver and other cells for energy or stored as glycogen for later use. The level of glucose in the bloodstream is regulated by 2 pancreatic hormones, insulin and glucagon. Insulin is released when glucose levels rise. Insulin acts by increasing glycogenesis, lipogenesis, and glycolysis, causing a decrease of glucose in the bloodstream. Glucagon is released when glucose levels fall, causing the liver to release stored glucose (glycogen) into the bloodstream (glycogenolysis), thereby increasing the level of glucose in the bloodstream. Hemoglobin A1c (HbA1c), also called glycosylated hemoglobin, is a hemoglobin compound produced when glucose reacts with the amino group on a hemoglobin molecule forming a ketoamine. The glucose molecule is attached to one or both N-terminal valines of the β-polypeptide chains of normal adult hemoglobin.1 The HbA1c formation is proportional to the blood glucose concentrations. Because the average red blood cell life is approximately 120 days, the glycosylated hemoglobin level reflects the average blood glucose level during the previous 2 to 3 months. Glucose testing is used to determine if an individual has hyperglycemia or hypoglycemia. A high fasting glucose level (≥126 mg/dL) and/or a high HbA1c level (>6.5%) might indicate that an individual has diabetes mellitus. HbA1c is a reliable method of monitoring long-term diabetes mellitus control; it determines the average blood glucose level of an individual during a period of approximately 3 months. Normal values range from 4.0% to 6.0%. Results of a study2 have shown the strong linear relationship between average blood glucose levels and HbA1c levels. Current American Diabetes mellitus Association guidelines recommend that a HbA1c test be performed at least twice yearly on patients who are meeting treatment … [↵][1]* To whom correspondence should be addressed. E-mail: vfreeman{at}utmb.edu [1]: #xref-corresp-1-1