What is a key diagnostic criterion for diabetes mellitus regarding HbA1c levels?

The criterion stating that HbA1c levels of 6.5% or more indicate diabetes is based on established diagnostic guidelines. The HbA1c test measures the average blood glucose levels over the past two to three months, providing an indication of long-term glucose control.

Specifically, an HbA1c level of 6.5% or greater is commonly used as a threshold for diagnosing diabetes mellitus as it correlates with blood glucose levels indicative of diabetes. This cutoff helps to identify individuals who have consistently high blood sugar levels that qualify for a diabetes diagnosis.

In contrast, levels under 5.7% are considered normal, while levels between 5.7% and 6.4% suggest an increased risk of diabetes (prediabetes), but do not confirm a diagnosis of diabetes itself. Therefore, the correct answer is supportive of the diagnostic criteria established by the American Diabetes Association and reflects an important aspect of managing and diagnosing diabetes.