HbA1c is a common blood test used in diagnosing and treating diabetes.

Glycated hemoglobin (HbA1c) reflects the average plasma glucose concentration over the preceding 2 to 3 months. It measures the percentage of hemoglobin A that has glucose non-enzymatically attached to its beta-chains. This test is a superior indicator of long-term glycemic control compared to a single fasting glucose measurement. It is standardized by the National Glycohemoglobin Standardization Program (NGSP) to ensure clinical accuracy across different laboratory settings. Rationale: A. True is the correct answer because HbA1c is a gold-standard diagnostic and monitoring tool for diabetes mellitus. An HbA1c level ≥ 6.5% is diagnostic for diabetes according to the American Diabetes Association. It is used in clinical practice to assess the effectiveness of pharmacotherapy and lifestyle modifications in maintaining euglycemia over an extended period. B. False is incorrect because it ignores the central role of HbA1c in modern endocrinology. Unlike daily glucose monitoring, HbA1c is not affected by recent food intake or acute stress, making it a reliable diagnostic metric. Denying its use would contradict standard clinical guidelines for the management of type 1 and type 2 diabetes.