Glycemic Variability: What Does Hemoglobin A1c Not Reveal About Clinical Risk?

Abstract

Introduction: Glycated hemoglobin (HbA1c) is widely used to assess glycemic control; however, it does not fully characterize glucose fluctuations or episodes of hypoglycemia and hyperglycemia. Objective: To analyze the scientific evidence on glycemic variability, its relationship with HbA1c, and its implications for clinical risk assessment in patients with diabetes mellitus. Methods: An integrative literature review was proposed to synthesize original studies, systematic reviews, meta-analyses, and clinical guidelines addressing glycemic variability and continuous glucose monitoring. Results: The reference literature indicates that metrics such as time in range, time below range, time above range, and glycemic coefficient of variation complement HbA1c by characterizing glucose fluctuation patterns and identifying clinically relevant glycemic events. However, the independent prognostic contribution of glycemic variability to long-term outcomes remains uncertain. Conclusion: Integrating HbA1c with continuous glucose monitoring metrics may improve the assessment of metabolic control and support individualized treatment. Nevertheless, these indicators should be interpreted in the clinical context and in light of the limitations of the available evidence.