Background: Insulin glargine and insulin detemir are the most commonly prescribed basal insulins in the United States. While these analogs chemically differ, clinical trials have established no significant difference in efficacy. However, controversy remains as to whether the 2 agents are comparable with regard to unit equivalency. Objectives: To determine the ratio of glucose lowering between insulin detemir and insulin glargine. Methods: This institutional review board-approved, single-center, retrospective, case-crossover study was conducted in patients with diabetes mellitus with inpatient admissions between June 30, 2014, to July 1, 2015. Patients must have received both insulin detemir and insulin glargine on either the same or separate hospital visits. A blood glucose–lowering ratio for both insulin glargine and insulin detemir was calculated for each patient based off of up to 5 days of fasting blood glucose values and the total number of units of insulin administered. Results: Fifty-two patients were included in this study. No significant difference was found in the blood glucose–lowering ratio between insulin glargine (0.23 mg/dL/unit) as compared with insulin detemir (0.16 mg/dL/unit; P = .08). Conclusion: No difference was found in the blood glucose–lowering ratio between insulin glargine and insulin detemir. The results of this study suggest that conversion between insulin glargine and insulin detemir using a 1:1 ratio in an acute care setting may be appropriate.