We have read the letter about our recently published report, "Clinical and Biochemical Characteristics of Elderly Patients With Hyperglycemic Emergency State at a Single Institution" 1). If it was not clear how the authors distinguished between diabetic ketoacidosis (DKA) with hyperglycemic hyperosmolar state (HHS) and mild DKA, patients were defined as having both DKA and HHS if they had a serum osmotic pressure of 320 mOsm/kg or higher, as well as an arterial blood pH of less than 7.30 or a bicarbonate level of less than 18 mEq/L. This group showed hyperosmolality (>320 mOsm/kg) as an important diagnostic criteria of HHS but also showed components of ketoacidosis. The patients who showed significant overlap between DKA and HHS were classified as having DKA with HHS. This was clearly distinguished from mild DKA. This is the similar definition used for DKA with HHS in previous studies referenced by the authors, such as those by MacIsaac et al. 2) and Kim et al. 3) .The anion gaps (mean±standard deviation [range]) for the DKA, DKA with HHS, and HHS groups were 22.6±8.4 (7-30), 20.8±4.9 (3-23), and 14.7±6.8 (3-23), respectively, and the pH ranges were 6. 92-7.28, 6.98-7.46, and 7.32-7.50, respectively.