Introduction <p>Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized primarily by insulin resistance and hyperglycemia, often leading to multiple complications. Sleep disturbances, including insomnia and sleep apnea, are prevalent in patients with T2DM and are associated with poorer glucose metabolism. Despite research examining the relationship between glucose metabolism, body composition, and sleep quality, the underlying mechanisms remain unclear, particularly within patients with T2DM.</p> Methods <p>This study involved 269 newly diagnosed patients with T2DM from January to June 2024. Data collected included demographic information, clinical variables, glycemic markers, and body composition analyses. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI), categorizing participants into poor (PSQI-H) and good sleep quality (PSQI-L) groups. Univariate and multivariate regression analyses, along with mediation analysis, were performed using SPSS 26.0 and R software to explore associations between sleep quality, glycemic markers, and body composition.</p> Results <p>Significant correlations were found between PSQI scores and glycemic markers such as HbA1c, HOMA-IR, and postprandial blood glucose levels, showing that poorer glucose control was correlated with worse sleep quality. Mediation analysis suggested that body composition, particularly the trunk-to-limb fat mass ratio, may act as a statistical mediator in the relationship between glucose metabolism and sleep quality.</p> Conclusions <p>Our findings highlight the complex relationship between glucose metabolism, body composition, and sleep quality in patients with T2DM. Targeting glucose regulation and body composition may be explored in future studies as potential approaches to improve sleep quality in individuals with T2DM.</p> Trial Registration <p>Clinical ChiCTR1900022768.</p>