Which of the following conditions is indicated by a hemoglobin A1c greater than 6.5%?

A hemoglobin A1c level greater than 6.5% is used as a diagnostic criterion for diabetes mellitus. This measurement reflects the average blood glucose levels over the past two to three months, and a value at or above this threshold indicates that a person has diabetes. In the context of diagnosing diabetes, an A1c of 6.5% or higher suggests that the individual's blood sugar levels have been consistently elevated.

This classification is grounded in guidelines established by organizations such as the American Diabetes Association, which consider an A1c level of 5.7% to less than 6.5% as indicative of prediabetes. Normal glucose tolerance is characterized by A1c values below 5.7%. Insulin resistance, while it can be a part of the pathophysiology of diabetes, does not have a specific A1c threshold and is not a standalone diagnosis associated with A1c levels.

Thus, an A1c greater than 6.5% is a clear indication of diabetes mellitus, signaling the need for further evaluation and management of the individual's blood glucose levels.