1. Provision of informed consent prior to any study specific procedures

2. Type2 diabetic patients had been on stable, maximum tolerated doses of metformin (≧1500mg/d, ≧8 weeks)

3. Male or female age ≧ 18 years and ≦70 years old

4. HbA1c ≧7.0 and ≦10%

5. BMI ≧ 24 kg/m2

1. Known or suspected allergy to trial products or related products.

2. Impaired renal function defined as serum-creatinine ≥ 1.5 mg/dl (≥ 133 umol/l).

3. Acute or chronic disease which may cause tissue hypoxia such as respiratory failure or shock.

4. Abnormal liver function, alanine transaminase or aspartate aminotransferase ≥ 3 fold normal upper limit, Total bilirubin ≥ 2 normal upper limit, acute alcohol intoxication, alcoholism.

5. Subjects has a clinically significant, active (or over the past 12 months) cardiovascular history (including a history of myocardial infarction (MI), arrhythmias or conduction delays on ECG, unstable angina, or decompensated heart failure (New York Heart Association-class Ⅲ and Ⅳ).

6. Proliferative retinopathy or muscular oedema requiring acute treatment.

7. Pregnant or positive pregnancy test at screening, nursing mother, or unwillingness to use adequate contraception (adequate contraceptive measures are sterilization, intrauterine device, oral contraceptives or barrier methods).

8. Treatment with systemic corticosteroids within the past two months prior to screening.

9. Type 1 diabetes mellitus.

10. Receipt of any investigational drug within 1 month prior to this trial.