© TÜBİTAK.Background/aim: The aim of present study was to investigate the dynamic thiol/disulfide homeostasis as oxidative stress marker in diabetic ketoacidosis (DKA). Materials and methods: A total of 77 participants consisting of 32 patients with DKA and 45 healthy volunteers were included in the study. Thiol/disulfide homeostasis (TDH) [total thiol-native thiol/disulfide changes] were measured in both groups (patient group and control group) using a brand new method developed by Erel and Neselioglu. Half of the difference between total thiol and native thiol concentrations gives the amount of disulfide bond. Results: Total thiol, native thiol, and disulfide levels in blood were found to be low. The levels of total thiol (P < 0.001) and native thiol (P < 0.001) were significantly lower in patients with DKA than in the control group. At the same time, the level of disulfide was nonsignificantly lower in the patient group than the control group (P = 0.388). The level of IMA was higher in the patient group than in the control group (P < 0.001). Conclusion: The total thiol, native thiol, and disulfide levels in DKA decrease in favor of oxidative stress.