Background: Cardiovascular autonomic neuropathy (CAN) represents a significant yet frequently under-diagnosed complication of diabetes mellitus (DM), arising from impaired autonomic regulation of the cardiovascular system, excluding other etiologies. Early detection of CAN is crucial, as prompt interventions targeting lifestyle modification, glycemic control, and cardiovascular risk reduction may decelerate or potentially reverse disease progression. Materials and Methods: This cross-sectional study encompassed 60 consecutive patients with diabetes mellitus, diagnosed in accordance with the American Diabetes Association (ADA) criteria. CAN was assessed utilizing Ewing’s battery of five standard bedside autonomic function tests, which evaluate both sympathetic and parasympathetic activity. Results: CAN was identified in 53 patients (88.3%). Of these, 38.3% exhibited early CAN, 38.3% had definite CAN, and 7% presented with severe CAN. The most prevalent abnormal autonomic test was the expiration–inspiration (E:I) ratio, indicative of parasympathetic dysfunction, observed in 75% of patients. QTc interval prolongation on ECG demonstrated high specificity for diagnosing and grading CAN severity, although sensitivity was comparatively low. Conclusion: CAN is highly prevalent among individuals with diabetes mellitus and is associated with an elevated risk of mortality. Routine screening for CAN at the time of diabetes diagnosis and periodic follow-up, as advocated by the ADA, is imperative. Early glycemic optimization and lifestyle interventions may aid in preventing CAN-related cardiovascular complications. Keywords: Cardiac autonomic neuropathy, Diabetes mellitus, Ewing’s battery, QTc interval

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