the study objective: to explore the efficacy of acarbose and metformin on glucose fluctuations as add on therapy in type 2 diabetes patients inadequately controlled with premix insulin.

Study Design:Prospective, parallel group, active-control, randomized, open-label.

Study Organization:Single-center in China. Endocrinology and metabolism department of 6th affiliated hospital of Shanghai Jiaotong university Study Population: Type 2 diabetes inadequately controlled by premix-insulin therapy,40 patients per arm(acarbose add on/ metformin add on) both acarbose and metformin are widely used with premix-insulin in clinical practice, for the better glucose control and lower hypoglycemia incident.

Acarbose delay the absorption of digested carbohydrates from the small intestine and thus lower both postprandial glucose and insulin levels which sequently improve glucose fluctuation Metformin improve the insulin resistance reduce the gluconeogenesis, glucose output and thus lower the fasting glucose

Inclusion Criteria:

• Diagnosed T2DM patients (WHO, 1999).
• Premix Insulin therapy for more than 3 months, the daily dosage of insulin >20IU and <1IU/kg
• 30 ≤Age ≤ 70 years old, male or female
• 7.0 ≤ HbA1c ≤10.0%
• 18.5≤ BMI ≤ 35 kg/m2
• Written Informed consent

Exclusion Criteria:

• Subject with type 1 diabetes or gestational diabetes mellitus and other specific types DM
• Those who can not tolerate AGI or who is suffering GI disease
• Metformin contradiction
• Concomitant 2 oral anti-diabetes medicine, or 1 OAD with maximum dose
• Subject with repeated severe hypoglycemia and/or unawareness of hypoglycemia
• Known or suspected allergy to trial product(s) or related products
• Females of child bearing potential who are pregnant, breast-feeding or have the intention of becoming pregnant or not using adequate contraceptive methods throughout the trial
• Impaired liver function,
• Any other clinically significant condition or major systemic diseases, including serious coronary heart disease, cardiovascular disease, cancer, TB, acute infection
• Uncontrolled hypertension
• Concomitant treatment which influences blood glucose
• Impaired renal function