A1C refers to glucose-modified hemoglobin. A1C is also known as hemoglobin A1c or HbA1c. Hemoglobin is a protein in red blood cells that carries oxygen to cells in the body. Glucose molecules in the blood react with hemoglobin and permanently modify the protein. The level of glucose-modified hemoglobin is proportional to the level of glucose in the blood and can therefore be used clinically to examine glucose levels over a certain amount of time. The A1C test is used to diagnose diabetes and to monitor blood glucose control in diabetic patients.
Red Blood Cell Life Cycle
Red blood cells typically live between 100 and 120 days. They are made in the bone marrow and are released into the bloodstream. At the end of the life cycle of a red blood cell, the cell is engulfed by macrophages and the hemoglobin is broken down and recycled. The amount of glucose-modified hemoglobin in red blood cells can be used as a measurement of the average amount of glucose in the blood for 100 to 120 days.
How to Interpret Laboratory Results
A1C levels are reported as a percentage. Average levels in non-diabetic people are between 4 and 5.9 percent. Diabetes is diagnosed if the A1C level is equal to or greater than 6.5 percent. The American Diabetes Association recommends that patients with type II diabetes have an A1C level below 7 percent, and it should be tested at least twice a year. The A1C test often includes an estimated average glucose (eAG). This is a calculation based on the A1C levels and is reported in mg/dL or mmol/L.
What are the Risks Associated With an Elevated A1C?
If A1C levels are consistently elevated, there is an increased risk of diabetes complications. These complications include cardiovascular disease; kidney, nerve and eye damage; and skin infections. Clinical trials have shown that decreasing A1C levels does reduce the risk of kidney, nerve and eye damage.
What Does an A1C Test Not Tell You?
The A1C test will not provide any information on acute increases or decreases in blood glucose. Because of this, the A1C test does not replace regular blood glucose monitoring.
Who Should Not Have an A1C Test?
The A1C test result is based on a normal red blood cell life cycle and should not be conducted in individuals who are pregnant, have given blood recently or have a red blood cell disorder such as hemolytic anemia.
