The aim of the study is to compare the FGM glycemic profiles in patients with type 2 diabetes mellitus treated with sitagliptin and acarbose.

In this study, 60 patients with type 2 diabetes were randomly divided into group A or group B after stable glucose control. Flash Glucose Mornitoring(FGM) will be used in patients with two groups. Patients in group A were given sitagliptin and metformin for the first two weeks, and then were treated with acarbose and metformin for the second two weeks. FGM was used to monitor glycemic variations during the whole four weeks. The opposite therapy was true for patients in group B.

Inclusion Criteria:

1. Participate voluntarily and sign the subject informed consent before the test.
2. Patients with type 2 diabetes, aged 18-75 years, meeting the diagnostic criteria of WHO1999, have not been treated with any hypoglycemic drugs.
3. No acute complications such as diabetic ketoacidosis and diabetic hyperosmolar syndrome.
4. Subjects are able and willing to undergo FGM examination, diet and exercise regularly.

Exclusion Criteria:

1. Patients allergic to insulin.
2. Impaired liver and renal function, ALT 2.5 times higher than the upper limit of normal value;Serum creatinine was 1.3 times higher than the upper limit of normal.
3. A history of drug abuse and alcohol dependence within the past 5 years.
4. Systemic hormone therapy was used in recent 3 months.
5. Patients with poor compliance and irregular diet and exercise.
6. Patients with infection and stress within four weeks.
7. Patients who cannot tolerate flash glucose mornitoring(FGM).
8. Patients who are pregnant, nursing or preparing to become pregnant.
9. Any other apparent condition or comorption as determined by the investigator, such as severe heart and lung disease, endocrine disease, neurological disease, tumor disease, other pancreatic disease, history of mental illness.