Objective: Blood ketone monitoring is commonly used in the management of diabetic ketoacidosis (DKA). However, bedside ketone meters have limited availability in hospitals. This study aimed to clarify the correlation between blood ketones and blood gas analysis (BGA) in the treatment of DKA and thereby identify parameters that can be used as surrogates for blood ketones.Patients and Methods: This retrospective observational study included patients with DKA admitted to the JA Toride General Medical Center between November 2021 and March 2024. Multiple regression analysis was performed using blood ketone levels as the objective variable and BGA indices as explanatory variables. Additionally, the study evaluated 1) the time course of ketone levels and BGA indices during the DKA treatment and 2) the correlation between ketone levels and the BGA indices.Results: Sixteen patients were enrolled. Multiple regression analysis showed that the corrected anion gap (cAG), defined as the anion gap minus lactate concentration, was a significant predictor of blood ketones. Among pH, HCO3−, and cAG, only cAG had significant regression coefficients (−0.061 [95% confidence interval (CI): −3.49 to 1.98], −0.233 [−0.156 to 0.0118], 0.636 [0.129 to 0.246], respectively; coefficient of determination: 0.765). The correlation coefficient between cAG and blood ketone levels was high (0.9694).Conclusion: cAG levels strongly correlate with blood ketone concentrations and may serve as a surrogate marker for blood ketones in the management of DKA. Because measurements of the anion gap and lactate concentrations are inexpensive and widely available in most medical facilities, cAG is a promising indicator for DKA management.