Basal Insulin Type and Risk of Diabetic Ketoacidosis in People with Type 1 Diabetes: A Case-Control Study

Introduction: This study aimed to evaluate the association between home basal insulin therapy and the risk of diabetic ketoacidosis (DKA) in individuals with type 1 diabetes (T1D). Methods: We conducted a retrospective 1:1 matched case-control study including patients with T1D admitted for DKA between 2011 and 2024 at a tertiary hospital. Cases (n = 97) were matched by age, sex, diabetes duration, and diabetic retinopathy with controls without a history of DKA (n = 97). Clinical and therapeutic information was collected, including the type of basal insulin used. Multivariable logistic regression models were constructed and adjusted for relevant variables, such as HbA1c, body mass index, and treatment with SGLT-2 inhibitors. Results: Treatment with insulin degludec was initially associated with a lower risk of DKA (OR 0.41; 95% CI: 0.20–0.85; p = 0.016), although this association lost significance after multivariable adjustment (OR 0.47; 95% CI: 0.18–1.20; p = 0.114), with HbA1c emerging as the main confounder. Insulin pump therapy and SGLT-2 inhibitor use were significantly associated with a higher risk of DKA. Patients with overweight or obesity presented a lower risk compared with those with normal weight. Conclusions: Our findings suggest that the type of basal insulin may influence the risk of DKA, although this effect appears to be conditioned by the degree of glycemic control. The potential protective effect of long-acting insulins such as degludec requires confirmation in prospective studies.