Objective: In this study, we aimed to investigate the effect of diabetes-related metabolic changes and chronic complications on lower urinary tract (LUT) functions. Materials and Methods: The study included 286 adult patients with type 1 and type 2 diabetes mellitus (DM). All patients' demographic data, diabetes-specific history, laboratory and physical examination findings were recorded. All the data were compared with uroflowmetric parameters and the scores of questionnaires used for evaluation of LUT symptoms and functions. Results: In the presence of diabetic peripheral neuropathy (DPN), average urinary flow rate (Q ave), International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) score and the Overactive Bladder-questionnaire Short Form (OAB-q SF) score were significantly affected. In the presence of stage 3 or over diabetic nephropathy (DN), ICIQ-SF score was significantly higher. Also, in elderly group, Q ave and OAB-q SF score were significantly affected. The Q ave was lower both in patients who underwent any surgery due to diabetic complications and in patients with DM-related diseases. Q ave and OAB-q SF score were significantly lower in males. Type 2 DM was associated with postvoid residual (PVR) increase and Q ave decrease. Poor glycemic control was associated with lower OAB-q SF score. Finally, vitamin D deficiency was found to be associated with an increase in PVR volume. Conclusion: The present study showed that DPN, stage 3 or over DN, aging, DM-related diseases and surgeries, male gender, type 2 DM, poor glycemic control and vitamin D deficiency cause a tendency to develop any kind of LUT dysfunction.