What is the significance of glycosylated hemoglobin (A1C) in the diagnosis of diabetes mellitus?

Glycosylated hemoglobin (A1C) is significant in diagnosing diabetes mellitus as it reflects the average blood glucose levels over the past 2 to 3 months. This test helps assess long-term glucose control in patients, providing a clearer picture of their glycemic status compared to a single blood glucose measurement.