The ADA guidelines indicate that one of the criteria for screening to help diagnose diabetes is a Hb A1C level of ≥6.5%. Moreover, the ADA indicates that the glycemic target for nonpregnant adults with diabetes is <7.0% and lowering A1C below or around 7.0% has been shown to reduce microvascular complications and macrovascular disease. Therefore, a Hb A1C level that is <7.0% indicates glycemic control for most adults with diabetes.
The ADA also issues caution on the limitations of the A1C test. Because of the variability in the measurement, clinicians should exercise judgment when using A1C as the sole basis for assessing glycemic control. The A1C test can give skewed results in people with certain genetic traits that alter the molecules in their red blood cells and can produce a disagreement between A1C and blood glucose levels. The ADA emphasizes that health care providers need to be aware of these limitations and to consider alternate diagnostic tests (fasting plasma glucose test or oral glucose tolerance test) if there is a disagreement between A1C and blood glucose levels.
ADA recommendations for A1C testing include:
- For many nonpregnant adults, the reasonable goal is an A1C of <7.0%.
- Providers may suggest more stringent A1C goals, such as <6.5%, for selected individuals if the goal can be achieved without significant hypoglycemia or other adverse effects.
- Less stringent A1C goals, such as <8.0%, may be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, or other conditions that may make the goal difficult to achieve.
- To avoid misdiagnosis or no diagnosis, the A1C test should be performed using a method that is certified by the NGSP and standardized to the Diabetes Control and Complications Trial (DCCT) assay.
- Marked discordance between measured A1C and plasma glucose levels should raise the possibility of A1C assay interference and consideration of using an assay without interference or plasma blood glucose criteria to diagnose diabetes.
- Less stringent Hb A1C goals than the general goal of <7.0% may also be appropriate for patients with a history of severe hypoglycemia, limited life expectancy, advanced microvascular or macrovascular complications, and those individuals with longstanding diabetes who are not able to consistently achieve the general goal of <7.0%.
4. American Diabetes Association. "Standards of Medical Care in Diabetes—2024." Clinical Diabetes, vol 47, issue 1, January 2024. https://diabetesjournals.org/care/issue/47/Supplement_1.
