Exploring the Relationship Between Neutrophil-to-Lymphocyte Ratio and Glycemic Control in Type 2 Diabetes Mellitus: A Cross-Sectional Analysis

Background/Objectives: The neutrophil-to-lymphocyte ratio (NLR) is an emerging inflammatory biomarker associated with various metabolic disorders, including type 2 diabetes mellitus (T2DM). While poor glycemic control is linked to increased risk of complications, the relationship between glycemic status and NLR remains insufficiently characterized. This study aimed to assess the association between NLR and glycemic control in T2DM patients by comparing those with good glycemic control (GGC; HbA1c ≤ 7%) and poor glycemic control (PGC; HbA1c ≥ 7.1%). Methods: A retrospective cross-sectional study was conducted on 2907 T2DM patients from a tertiary care center. Patients were categorized into GGC (n = 1500) and PGC (n = 1407) groups based on HbA1c values. The mean age of participants was 53.53 ± 18.86 years in the GGC group and 54.31 ± 18.40 years in the PGC group, with comparable sex distribution between groups. Data were retrieved from electronic medical records and NLR was calculated using complete blood counts. Descriptive statistics were computed, and group comparisons were performed using Mann–Whitney U and independent t-tests. Spearman correlation and receiver operating characteristic (ROC) analysis were also performed. A p-value < 0.05 indicated significance. Results: The PGC group exhibited significantly higher mean NLR (3.96 ± 4.53) compared to the GGC group (3.23 ± 3.80) (p < 0.001). Median and interquartile range values confirmed this difference, and both parametric and non-parametric analyses supported the findings. Spearman correlation demonstrated a weak but statistically significant association between HbA1c and NLR (r = 0.101, p < 0.001). ROC analysis showed limited discriminatory ability of NLR (AUC = 0.560). Exploratory CRP results further suggested a link between inflammation and impaired glycemic control. Conclusions: NLR was significantly elevated in T2DM patients with moderate-to-poor glycemic control. This suggests that NLR may serve as a simple, cost-effective, and accessible marker of systemic inflammation and glycemic status. However, the effect size was small, and its discriminatory ability was limited, indicating that NLR should be interpreted as a supportive marker rather than a standalone clinical tool.