ObjectiveTo investigate the clinical heterogeneity and auto-immunologic state in patients with diabetic ketosis (DK) or diabetic ketoacidosis (DKA). MethodsDiabetic patients who presented with DK/DKA were recruited from West China Hospital of Sichuan University from January 1, 2000, to December 31, 2008. We analyzed the clinical classification, biochemical profiles, and auto-immunologic state of the patients. ResultsAmong them, 257 (15.0%) patients had type 1 diabetes, while 883 (51.6%) with type 2 diabetes, and 515 (30.1%) could be typed as "atypical diabetes" or "untying diabetes". The average age of hospitalized patients with type 1 diabetes was (31.1±13.5) years, which was significantly lower than that of the type 2 diabetes patients [(58.1±13.2) years] (P＜0.001). The most common contributing factor for DK/DKA was infection, followed by noncompliance with therapy. Glutamic acid decarboxylase antibody positive rate was 4.37% in patients with "atypical diabetes", which was similar with type 2 diabetes group (2.69%, P=0.79), but lower than that of the patients with type 1 diabetes (13.79%, P＜0.001). ConclusionsWe conclude that DK or DKA can occur not only in type 1 diabetic patients but also in patients with type 2 diabetes under infection or stress condition. DK/DKA patients have a high clinical heterogeneity. The auto-immunologic state and β-cell function have significant implications for the diagnosis and classification of diabetes.