This study will evaluate whether the addition of sitagliptin treatment provides additional decrease in HbA1C levels and increase in goal attainment in patients with inadequate glycemic control on their current oral anti-glycemic therapy in real world practice.

To explore the change of glycemic control (HbA1c or FPG) before and after 24 weeks of Sitagliptin treatment in Type 2 Diabetic patients who have started Sitagliptin as add on therapy during the index period and received Sitagliptin continuously* for at least 24 weeks.

Inclusion Criteria:

1. All subjects diagnosed of type 2 diabetes (ICD-9 code= 250.0; 250.1; 250.2; 250.3; 250.4; 250.5; 250.6) and have been followed up regularly in the study center who have started to receive Sitagliptin as an add-on treatment to their prior regimen during the index period
2. Subjects must be on a stable dose of all antidiabetic regimens, with stable dose defined as "at least 3 months with no therapy/dose change" prior to adding sitagliptin
3. Subjects in whose medical records a minimum core data set can be found.
4. Outpatient

Exclusion Criteria:

1. Subjects with type 1 DM
2. Subjects have been treated with insulin regularly
3. Subject with DM which results from other general diseases, e.g. surgery, pharmaceutical products, malnutrition, infections and other conditions
4. Subjects who participated in a clinical trial or other clinical study during the index period

Subjects with ICD-9 diagnostic codes of T2DM plus any prescription record of the anti-glycemic drugs included in the hospital formulary during the study period will be extracted from the hospital outpatient electronic database. Sitagliptin users who stayed with Sitagliptin for at least 24 weeks will then further identified from this diabetes cohort for efficacy analysis.