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Background: Hypertension (HTN) is linked to cardiac dysautonomia that can end up as life-threatening arrhythmias. The same can be screened by simple electrocardiogram (ECG)-based QTc (QT corrected for heart rate) interval which indicates repolarization abnormality. We quantified QTc interval among treated hypertensives in comparison to controls, testing effect of age, gender, and blood pressure. Methods: We conducted a cross-sectional study was done at a tertiary care teaching hospital of Gujarat, India, on 142 hypertensives on monotherapy (60 males, 82 females) and 72 age-, sex-, and time-matched normotensives. ECG was recorded with minimum 10 complexes of Lead II. QTc was derived from average of 10 values, using Bazett's formula. QTc > 0.43 s in male and > 0.45 s in female was considered abnormal. Results: Hypertensives (mean age 40 and duration 5 years) had significantly higher QTc value than normotensives among males (0.42 vs. 0.40, P < 0.001), females (0.44 vs. 0.41, P < 0.001), and in total (0.43 vs. 0.41, P < 0.001) with 24% prevalence of ECG-based left ventricular hypertrophy. Hypertensives had odds ratio 1.63 in males (P = 0.15), 23.71 in females (P = 0.003), and 3.83 in total (P < 0.001) for prolonged QTc. QTc values were significantly affected by increasing age amongst hypertensives but not by duration of HTN or current blood pressure. Conclusions: Our study showed a high prevalence of prolonged QTc, both qualitatively and quantitatively, in hypertensives on monotherapy with poor pressure control, associated with female gender and age but not duration or blood pressure. This underscores high risk of repolarization abnormality induced future event, suggesting QTc screening as primary prevention. [ABSTRACT FROM AUTHOR]