Introduction Diabetic ketoacidosis is a life-threatening condition that requires prompt management. Objectives We aimed to assess the impact of adherence to potassium replacement protocol according to the guidelines of Diabetes Poland on the duration of diabetic ketoacidosis (DKA) treatment. Patients and methods This retrospective analysis included 242 adults (median age, 27 years; range, 21-38 years). Nonadherence to potassium replacement protocol was assessed, along with the relationship between nonadherence and duration of DKA management. Nonadherence to the protocol was defined as too low or too high doses of potassium compared with the recommended potassium replacement protocol. Results The median duration of DKA treatment was longer in the nonadherent group than in the adherent group: 37 hours (interquartile range [IQR], 27-48) and 30 hours (IQR, 17-43), respectively (P = 0.005). Treatment duration correlated positively with nonadherence to potassium replacement protocol (r = 0.18; P = 0.005) and severity of DKA (r = 0.52; P <0.0001). Stepwise multivariate linear regression analysis indicated nonadherence to the protocol (β = 0.14; P = 0.02) and severity of DKA (β = 0.43; P <0.0001) as predictors of treatment duration, after adjustment for body mass index and age (R2 = 0.28; P <0.0001). Conclusions Nonadherence to potassium replacement protocol leads to prolongation of DKA management. Medical staff should be educated about the benefits of potassium replacement and precision in potassium administration and dosing in patients with DKA.