Association Between Neutrophil‐to‐Lymphocyte Ratio and Glycemic Control in Type 2 Diabetes Mellitus: An Updated Systematic Review and Meta‐Analysis

ABSTRACT Background Type 2 diabetes mellitus (T2DM) is increasingly seen as a chronic inflammatory state, with the neutrophil‐to‐lymphocyte ratio (NLR) studied as a new biomarker of systemic inflammation. Evidence links NLR to glycemic control, but its consistency and strength vary. This review summarizes data on NLR's relationship with glycemic indicators, such as hemoglobin A1c (HbA1c), across different T2DM glycemic states. Methods A systematic literature search was carried out in PubMed/MEDLINE, Scopus, Web of Science, and Embase through November 2025 to find studies that reported both NLR and glycemic control indicators in adults with T2DM. Data were systematically extracted based on predefined criteria. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were combined using random‐effects models. Heterogeneity was measured using the I² statistic, and robustness was assessed using sensitivity analyses. Publication bias was investigated using Begg's and Egger's tests, trim‐and‐fill analysis, and funnel plot examination. All statistical analyses were conducted using STATA 18 (StataCorp, College Station, TX, USA). Results The meta‐analysis consisted of 27 studies (37 comparisons) with a total of 48,714 individuals from 11 nations. NLR demonstrated a stepwise gradient with deteriorating glycemic control: poorly controlled T2DM (HbA1c > 7%) had higher NLR than well‐controlled T2DM (HbA1c ≤ 7%) ( p < 0.001), prediabetes (HbA1c 5.7–6.4%) ( p < 0.001), and normoglycemia (HbA1c ≤ 5.7%) ( p = 0.037). Conclusions NLR rises progressively with deteriorating glycemic control and is markedly raised in poorly controlled T2DM. These observations endorse NLR as an inexpensive, widely available inflammatory biomarker that can augment conventional glycemic measures in the clinical setting.