Which of the following glucose levels is diagnostic for diabetes mellitus according to HbA1c testing?

The diagnostic criteria for diabetes mellitus using HbA1c testing states that a value of 6.5% or higher indicates diabetes. This percentage reflects an average blood glucose level of approximately 140 mg/dL or higher over the previous two to three months, which aligns with the criteria set by the American Diabetes Association.

By establishing the threshold at 6.5%, the criteria encompass a balance between sensitivity and specificity to accurately identify individuals with diabetes while minimizing false positives. This threshold is crucial for initiating lifestyle interventions and pharmacological treatments to prevent potential complications associated with diabetes.

Lower HbA1c values, such as 6.0% or even 7.0%, do not meet the established criteria for a diagnosis of diabetes, as they may belong to the range indicating prediabetes or normal glucose metabolism. Higher values, like 8.0%, signify poorly controlled diabetes but are not used to establish a diagnosis; they rather indicate a need for more intensive management. Therefore, a HbA1c of 6.5% or greater is definitive for diagnosing diabetes mellitus.