Background: Uncontrolled diabetes leads to acute and chronic complications, both of which present to the emergency department (ED). Glycated hemoglobin (HbA1c) reflects glycemic history. This study was done to determine the correlation between acute diabetic complications and implications of HbA1c levels in ED. Materials and Methods: We conducted a prospective observational study between May 2019 and April 2020. Data was collected in a standard datasheet and analysed using Statistical Package for Social Sciences for Windows. Results: Our study included a total of 382 (0.5%) patients, among which 56% were male patients. Mean age was 57.9 (standard deviation ± 14.9) years. Based on their hemodynamic stability, majority (n = 291) were triaged as priority one. Acute diabetic complications included hypoglycemia-62% (238/382), diabetic ketoacidosis (DKA) - 26% (98/382) and hyperglycemic hyperosmolar state - 12% (46/382). Most common presenting complaints were unresponsiveness (49.7%) followed by breathing difficulty (31.6%) and fever (24.6%). Random blood sugar level at presentation was <70 mg/Dl in majority (62.3%) of them. Common precipitating factors were poor food intake (51%), infection (30%) and drug noncompliance (29.5%). Three-fourth of the study population was previously diagnosed to have diabetes mellitus and HbA1c >7 was seen in 227 (59%) patients. Bivariate and multivariate logistic regression analysis showed DKA (adjusted odds ratio [OR]: 5.2;95% confidence interval [CI]: 1.39–19.41; P = 0.014), noncompliance to medications (adjusted OR: 3.9; 95% CI: 1.4–10.76; P = 0.009) and poor oral intake (adjusted OR: 0.3; 95% CI: 0.14–0.59; P = 0.001) as independent predictors to have a HbA1c level >7. Approximately half (51.2%) the study population required admission while one patient died in the ED during resuscitation. Conclusion: Elderly male population were most commonly involved. Unresponsiveness was the most common presenting complain and hypoglycemia was the most common presenting clinical feature. Majority of the acute diabetic complications were precipitated by poor food intake, infection and noncompliance to medications. Hospital admission was warranted in majority of the study population. HbA1c in the ED is a useful parameter that would help plan further medication at discharge.