Objective To explore the application of serum β-hydroxybutyric acid(β-HB) in diagnosing Diabetic Ketoacidosis(DKA).Methods To detect the levels of serum β-hydroxybutyric acid、fasting blood glucose(FBG) and urine ketone in 96 diabetes without ketoacidosis,28 diabetic ketoacidosis,60 normal contrals.All results were compared.Results In diabetic ketoacidosis,the results of β-HB,FBG,positive ratio of ketone were respectively(1.75±1.77) mmol/L,(14.27±5.17) mmol/L and 85.7%.In group of diabetes without ketoacidosis,the results of β-HB,FBG were separately(0.275±0.34) mmol/L,(11.34±3.65) mmol/L,Urine ketone were negative.The levels of β-HB、FBG in diabetic ketoacidosis were significantly higher than those of other two groups(P 0.05).Conclusion Examination of serum β-HB can help diagnosis and treat diabetic ketoacidosis,Its sensitivity is higher than urine ketone.