Meta-analysis of sex differences in insulin therapy outcomes for adults with Type 1 and Type 2 diabetes

UNLABELLED: Sex differences in glycemic outcomes following insulin therapy remain underexplored despite biological and psychosocial factors that may influence individual responses. This systematic review examines sex-specific differences in glycemic control to guide personalized diabetes care and promote health equity. We searched PubMed, Scopus, Cochrane Library, and Google Scholar (August 2014-December 2025) for randomized and observational studies involving adults of both sexes on insulin. Twenty-four studies were included, with certainty of evidence assessed using GRADE. In type 1 diabetes, women showed no significant difference in achieving HbA1c <7% (RR 1.05, 95% CI 0.91 to 1.22; very low certainty) and toward higher time-in-range (SMD 0.78, -0.01 to 1.57; moderate certainty). In type 2 diabetes, men were more likely to achieve HbA1c targets (RR 0.86, 95% CI 0.72 to 1.03; low certainty), while women required higher weight-adjusted insulin doses (SMD 0.55, 0.23 to 0.86; very low certainty). Hypoglycemia risk showed opposing trends in inpatient (RR 0.78, 95% CI 0.33 to 1.83; very low certainty) versus outpatient settings (RR 1.08, 95% CI 0.61 to 1.89; low certainty) with substantial heterogeneity (I2>70%). These findings suggest that sex-related differences in glycemic outcomes vary by diabetes type and treatment context. Given the low certainty and heterogeneity of current evidence, results should be interpreted as hypothesis-generating. This review supports the consideration of biological sex within a broader, individualized diabetes management framework and highlights the need for future sex-stratified analyses with rigorous control of lifestyle and physiological factors. INTRODUCTION: Sex differences in glycemic outcomes following the same insulin therapy in diabetes remain underexplored. Numerous factors, encompassing both biological and psychosocial aspects, could potentially influence individual responses to insulin therapy. This systematic review examines sex-specific differences in glycemic control to guide personalized diabetes care and promote health equity. METHODS: PubMed, Scopus, Cochrane Library, and Google Scholar were searched (August 1, 2014-December 31, 2025) for randomized and observational studies. Eligible studies included adults of both sexes on insulin reporting sex-specific data for predefined outcomes. Data on glycated hemoglobin (HbA1c), blood glucose metrics, hypoglycemia, and insulin dose were extracted. Certainty of evidence was assessed using Grading of Recommendations, Assessment, Development and Evaluations. RESULTS: Twenty-four studies were included. In type 1 diabetes, women showed no significant difference in achieving HbA1c <7% (risk ratio (RR) 1.05, 95% CI 0.91 to 1.22; very low certainty) and toward higher time-in-range (standardized mean difference (SMD) 0.78, -0.01 to 1.57; moderate certainty). In type 2 diabetes, men were more likely to achieve HbA1c targets (RR 0.86, 95% CI 0.72 to 1.03; low certainty), whereas women required higher weight-adjusted insulin doses (SMD 0.55, 0.23 to 0.86; very low certainty). Hypoglycemia risk showed opposing trends in inpatient (RR 0.78, 95% CI 0.33 to 1.83; very low certainty) versus outpatient settings (RR 1.08, 95% CI 0.61 to 1.89; low certainty), with substantial heterogeneity (I >70%). CONCLUSION: Sex-related differences in glycemic outcomes under insulin therapy were observed, with patterns varying by diabetes type, treatment context, and outcome. Given the low certainty and heterogeneity of the evidence, these findings should be interpreted as hypothesis-generating rather than directive for clinical practice. The results support consideration of biological sex as one component within a broader, individualized diabetes management framework. Future studies should prioritize sex-stratified analyses with rigorous control of polypharmacy, body composition, and lifestyle factors to determine whether sex-specific insulin strategies provide meaningful clinical benefit. PROSPERO REGISTRATION NUMBER: CRD420251144696.