Background: Significant variability is reported as to the presence and quality of gastrointestinal (GI) symptoms in patients with type 1 diabetes (T1D). Objective: To assess reported GI symptoms and associated comorbidities in adults and children with T1D. Methods: The Gastrointestinal Symptom Scale (GISS) and a Visual Analog Scale (VAS) were used to assess GI symptom type and severity in 2,370 patients with T1D aged 8-45 years as part the screening phase of the Celiac Disease and Diabetes Dietary Intervention and Evaluation Trial (CD-DIET). Co-morbidities, including diabetes-related complications, were extracted from clinical records. The presence and severity of GI symptoms and relationships with demographic, clinical and other diabetes-related factors were evaluated. Results: Overall, 1368 adults (57.7%) aged 19-45 years and 1002 (42.3%) pediatric patients aged 8-18 years were studied. At least one GI symptom was reported in 34.1% of adults as compared with 21.7% of children (p<0.0001). Common symptoms in children included upper abdominal pain, lower abdominal pain and nausea while adults more frequently reported lower GI symptoms with females describing more severe symptoms. Overall, patients with ≥1 GI symptom were more likely to have diabetes complications when adjusted for age and sex (OR=1.41; 95% CI=1.1-1.7; p=0.002). Conversely, patients who reported diabetes complications such as nephropathy, retinopathy and/or cardiovascular disease were 1.94 (95% CI=1.49-2.52) times more likely to report GI symptoms. No association was observed between autoimmune conditions (including screen-detected celiac disease and reported thyroid disease) and GI symptoms. Conclusions: In this large screening study in a contemporary T1D cohort, significant differences were found between age groups with more frequent GI symptoms in adults. Significant associations were observed between GI symptoms and diabetes complications along with diabetes duration. Disclosure F.H. Mahmud: None. E. Nunes de Melo: None. A.B. Clarke: None. E. Assor: None. A. Parikh: None. A. Advani: Research Support; Self; AstraZeneca, Boehringer Ingelheim GmbH. Other Relationship; Self; Boehringer Ingelheim GmbH. B.A. Perkins: Advisory Panel; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH, Novo Nordisk Inc.. Advisory Panel; Self; Novo Nordisk Inc., Abbott. Speaker's Bureau; Self; Abbott, Janssen Pharmaceuticals, Inc.. Advisory Panel; Self; Insulet Corporation. Speaker's Bureau; Self; Insulet Corporation, Dexcom, Inc.. B.R. Shah: None. C.S. Zuijdwijk: None. C. McDonald: None. D. Mack: None. D. Koltin: None. E. Hsieh: None. E.M. Szentgyorgyi: None. F. Saibil: None. G. Mukerji: None. H.A. Lochnan: Research Support; Self; Amylin Pharmaceuticals, Boston Therapeutics, Inc., Sanofi. J. Gilbert: Other Relationship; Self; AstraZeneca, Boehringer Ingelheim GmbH, Eli Lilly and Company, Merck & Co., Inc., Novo Nordisk Inc., Janssen Pharmaceuticals, Inc., Sanofi. K. Bax: None. M.L. Lawson: None. M.D. Beaton: Advisory Panel; Self; Takeda Canada Inc., Janssen Pharmaceuticals, Inc., AbbVie Inc.. N.A. Saloojee: None. O. Lou: None. P.H. Gallego: None. R.L. Houlden: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Novo Nordisk Inc., AstraZeneca, Eli Lilly and Company. R. Aronson: Other Relationship; Self; Novo Nordisk Inc., Janssen Pharmaceuticals, Inc., Sanofi, AstraZeneca. Research Support; Self; Eli Lilly and Company, Becton, Dickinson and Company, Merck & Co., Inc., Senseonics, Boehringer Ingelheim Pharmaceuticals, Inc.. S.E. Kirsch: None. W.G. Paterson: None. Z. Punthakee: Research Support; Self; Amgen, Astra Zeneca/Bristol Myers Squibb, Lexicon, Merck, NovoNordisk, Sanofi. Speaker's Bureau; Self; Abbott, Astra Zeneca/Bristol Myers Squibb, Boehringer Ingelheim/Eli Lilly, Janssen, Merck, NovoNordisk, Pfizer, Sanofi. Advisory Panel; Self; Astra Zeneca/Bristol Myers Squibb, Boehringer Ingelheim/Eli Lilly, Dexcom, Janssen, Medtronic, NovoNordisk, Pfizer, Sanofi. M.A. Marcon: None.