Current guidelines for treatment of diabetic ketoacidosis (DKA) recommend administration of an intravenous bolus dose of insulin followed by a continuous infusion. This study was designed to investigate whether the initial bolus dose is of significant benefit to adult patients with DKA and if it is associated with increased complications. This was a non-concurrent, prospective observational cohort study of adult patients who presented with DKA in a 12-month period. Charts were divided into two groups depending on whether they received an initial bolus dose of insulin. Data on glucose levels, anion gap (AG), intravenous fluid administration (IVF), and length of stay (LOS) were collected. Primary outcome was hypoglycemia (need for administration of 50% dextrose). Of 157 charts, 78 received a bolus of insulin and were designated the treatment group, the remaining 79 formed the control group. Groups were similar at baseline and received equivalent IVF and insulin drips. There were no statistically significant differences in the incidence of hypoglycemia (6% vs. 1%, respectively, p = 0.12), rate of change of glucose (60 vs. 56 mg/dL/h, respectively, p = 0.54) or AG (1.9 vs. 1.9 mEq/L/h, respectively, p = 0.66), LOS in the Emergency Department (8 vs. 7 h, respectively, p = 0.37) or hospital (5.6 vs. 5.9 days, p = 0.81). Equivalence testing revealed no clinically relevant differences in IVF change, rate of change of glucose, or AG. Administration of an initial bolus dose of insulin was not associated with significant benefit to patients with DKA and demonstrated equivalent changes in clinically relevant endpoints when compared to patients not administered the bolus.