Introduction: Intravenous (IV) regular insulin treats acute hyperkalemia. No guideline recommendations exist on the appropriate dose to be administered to maximize safety and efficacy. Objectives: The objective of this study was to evaluate the safety and efficacy of IV regular insulin in patients who received 5 units of IV regular insulin to any dose greater than 5 units for acute hyperkalemia treatment. Methods: This was a single-center, retrospective, observational, cohort study. Patients were included if they were at least 18 years old, received greater than or equal to 5 units IV regular insulin, had pre-insulin potassium greater than or equal to 5.1 mEq/L and blood glucose measured within three hours before and 12 hours after insulin administration. The primary outcome was the incidence of hypoglycemia within 12 hours of insulin administration. Results: Eight-hundred and ninety-six charts were reviewed and 290 patients were included; 126 patients received 5 units and 164 patients received more than 5 units of IV regular insulin. Six patients (4.7%) who received 5 units experienced hypoglycemia compared to 23 patients (14%) who received greater than 5 units (P = 0.0014). Twenty-six of 29 (90%) who experienced hypoglycemia had renal impairment. Groups had a similar baseline mean potassium of 5.9 mEq/L (P = 0.32) and follow-up mean potassium of 5.3 mEq/L (P = 0.87). Conclusion: Patients who received 5 units of IV regular insulin had a lower incidence of hypoglycemia with a similar reduction in serum potassium when compared to patients who received doses greater than 5 units.