Correlation between Glycosylated Hemoglobin and Glycemic Variability in Patients with Type 2 Diabetes Mellitus

Abstract

Background & Objectives: Glycosylated hemoglobin (HbA1c) is commonly used to diagnose and monitor diabetes. Still, it has some drawbacks, such as being affected by blood disorders and failing to show changes in blood sugar levels throughout the day. This study examined how HbA1c relates to measures of blood sugar variability, with particular focus on Time in Range (TIR).

Methods: We conducted a cross-sectional study of 70 patients with type 2 diabetes. We collected their HbA1c levels and data from continuous glucose monitoring (CGM). Using the ambulatory glucose profile, we measured glycemic variability, including TIR, Time Below Range (TBR), Time Above Range (TAR), and Mean Amplitude of Glycemic Excursions (MAGE). We then analyzed the relationship between HbA1c and these CGM metrics.

Results: HbA1c was strongly linked to TIR (r = -0.88, p < 0.001) and TBR (r = -0.29, p < 0.01) and also showed a strong positive link with TAR (r = 0.91, p < 0.001) and MAGE (r = 0.85, p < 0.001). Even though some patients had HbA1c below 7.5%, only 55.5% had TIR above 70%. Also, 60% had TBR above 4%, indicating many were at risk of low blood sugar.

Interpretation & Conclusions: While HbA1c remains helpful for assessing overall blood sugar control, it does not reflect changes in blood sugar throughout the day. CGM metrics, especially TIR, give a fuller picture and should be used regularly in diabetes care.