OBJECTIVES: Type 2 diabetes, is a disease with a rising prevalence worldwide. A major burden of this disease would be shared by developing countries like Iran. Medications for diabetes mellitus need to be taken for the entire life and factors like efficacy, side effects, drug interactions and cost of therapy should be consider. This study was designed to evaluate the prescription pattern of anti-diabetic drugs in T2DM patients from 2006 to 2009 in Iran. METHODS: A retrospective study was undertaken on insured prescriptions during 4 years. All insured prescriptions which were collected in special software called Rx Analyst during the study period in the NCRUD were reviewed for prescriptions included anti-diabetic drugs. The brand names of drugs in prescriptions were decoded to generic names, according to standard Iran drug list. RESULTS: A total of 261,110,666 prescriptions were assessed in which 11,637,224 were detected to be included at least one dosage form of anti-diabetic medications. From all, 1,376,750 prescriptions had at least one injection form of Insulin and 10,260,474 of oral anti diabetic drugs. Trend evaluation of prescribing showed that the total number anti-diabetic medications were increased from 16,158,375 in 2006 to 4,268,444 in 2009. The portion of prescriptions with Insulin was 8%, 9%, 13% and 9% and for oral anti-diabetic drugs, it was 59%, 66%, 71% and 72%in 2006, 2007, 2008 and 2009, respectively. The total cost of Insulin during study period was 17,134,032 US$ and for oral anti-diabetic drugs was 84,682,039 US$ from national sales data. CONCLUSIONS: According to national sales data, total cost of anti-diabetic medications is about 100,00 times more than cost of these drugs in prescriptions. This huge gap shows irrational use of such medications. A multi interventional policy including educational, regulatory, managerial and financial strategies for professions and public should be planed to promote rational use of anti-diabetic medications.