Background
Introduction to the HbA1c Test
There are estimated to be 150 million diabetic patients worldwide, with 20 million in the United States alone. The best test of blood sugar control for people with diabetes is the hemoglobin A1c or HbA1c test and is recommended by the American Diabetes Association (ADA). Clinical studies such as the Diabetes Control and Clinical Trials (DCCT) showed that lowering HbA1c levels can delay or prevent the development of serious eye, kidney and nerve disease in people with diabetes. The study also showed that lowering HbA1c levels, by any amount, improves a person’s chances of staying healthy. Therefore, HbA1c is the most important test for health care providers to determine if a patient’s blood sugar is under control.
What is HbA1c and HbA1c testing?
HbA1c refers to a glucose bound hemoglobin A molecule. In blood, glucose can become attached to hemoglobin molecules in red blood cells. This process is called glycosylation. Once the glucose is attached, it stays there for the life of the red blood cell, which is about 60–90 days. The higher the glucose level in the blood, the more the glucose attaches to hemoglobins. The HbA1c test measures the amount of glucose attached to the hemoglobin in the red blood cells, and is expressed as a percentage of glucose bound hemoglobin over total hemoglobin concentration, or % of HbA1c. The HbA1c test can provide an assessment of average blood glucose control during the 60–90 days (2–3 months) prior to the test.
How often should HbA1c be tested?
The American Diabetes Association (ADA) recommends that all patients with diabetes mellitus should have HbA1c tests performed routinely. Since the results refl ect the level of glucose control over the previous 2–3 months, measurement approximately every 3 months is required to determine whether or not blood glucose control is improving.
What are healthy HbA1c levels?
Target HbA1c levels vary from person to person. A general range is summarized in Table 1 below:
