PURPOSE: To investigate the relationship between glucose fluctuation and erectile dysfunction (ED) in patients with type 2 diabetes mellitus (T2DM). METHODS: This cross-sectional study included 317 male patients with T2DM. Participants were categorized into non-ED group (76 cases) and ED group (241 cases) based on International Index of Erectile Function-5 (IIEF-5) scores. Patients were additionally segmented into quartiles based on time in range (TIR). Demographic and laboratory data were collected, and glucose fluctuation indicators were ascertained using flash glucose monitoring. RESULTS: The ED group exhibited significantly lower TIR and IIEF-5 scores compared to the non-ED group (P <
0.05). An increase in TIR levels corresponded with higher IIEF-5 scores and a significant reduction in ED incidence (P <
0.05). Spearman's correlation analysis indicated a positive correlation between IIEF-5 scores and TIR (r = 0.48, P <
0.01). Restricted cubic spline analysis revealed a negative linear association between TIR and ED (P for linearity <
0.05). Multivariate logistic regression analysis, after adjusting for confounding factors, confirmed that low TIR is an independent risk factor for ED (P <
0.05). CONCLUSION: Glucose fluctuation in T2DM patients correlate with ED, with low TIR being independently and positively associated with ED incidence, suggesting it may be a significant risk factor for ED in patients with T2DM.