To evaluate the incidence and risk factors for diabetic ketoacidosis (DKA) and related adverse events (AEs) in adults with type 1 diabetes treated with sotagliflozin adjunctive to insulin. Data from two identically designed, 52-week, randomized studies were pooled and analyzed for DKA, changes in β-hydroxybutyrate (BHB), and percentage of patients with BHB >0.6 and >1.5 mmol/L. The patients were administered placebo, sotagliflozin 200 mg, or sotagliflozin 400 mg once daily. A total of 191 ketosis-related AEs were reported, and 98 underwent adjudication. Of these, 37 events (36 patients) were adjudicated as DKA, with an exposure-adjusted incidence rate of 0.2, 3.1, and 4.2 events per 100 patient-years for placebo, sotagliflozin 200 mg, and sotagliflozin 400 mg. No patient died of a DKA event. From a baseline BHB of ∼0.13 mmol/L, sotagliflozin treatment led to a small median increase over 52 weeks (≤0.05 mmol/L at all time points). Of sotagliflozin-treated patients, approximately 47% and 7% had ≥1 BHB measurement >0.6 mmol/L and >1.5 mmol/L, respectively (vs. 20% and 2%, respectively, of placebo-treated patients). Subsequent to the implementation of a risk mitigation plan, annualized DKA incidence was lower versus preimplementation in both the sotagliflozin 200 and 400 mg groups. In patients with type 1 diabetes, confirmed DKA incidence increased when sotagliflozin was added to insulin compared with insulin alone. A lower incidence of DKA was observed following the implementation of an enhanced risk mitigation plan, suggesting that this risk can be managed with patient education. © 2020 by the American Diabetes Association.