OBJECTIVE: Diabetes mellitus is associated with an increased prevalence of GI symptoms, but the mechanisms underlying symptoms are poorly defined and controversial. We aimed to determine whether there is a relationship between GI symptoms and both diabetic complications and glycemic control. METHODS: We performed a cross-sectional questionnaire study of 1101 subjects with diabetes mellitus recruited from outpatient clinics (n = 209) and the community (n = 892). Data on eight GI symptom groups, complications of diabetes (retinopathy, neuropathy, nephropathy), and self-reported glycemic control were obtained from a validated questionnaire. Glycated hemoglobin was measured in 463 of the subjects. The association between diabetic complications, glycemic control, and GI symptoms was assessed using logistic regression analysis, adjusted for demographic and clinical factors. RESULTS: Of the 1101 subjects, 57% reported at least one complication. Diabetic complications were independently associated with both symptom complexity (number of symptom groups reported) (adjusted odds ratio = 1.92 per symptom group [95% CI = 1.51-2.45]) and seven of the eight GI symptom groups. For all symptom groups, the association was explained by self-reported symptoms of peripheral neuropathy. Poor glycemic control measured by both self-report and Hb A1c was an independent risk factor for upper GI symptoms, whereas other potential risk indicators, including duration and type of diabetes, were not significant. CONCLUSIONS: GI symptoms in diabetes mellitus may be linked to diabetic complications, particularly peripheral neuropathy, and to poor glycemic control.