OBJECTIVES: The primary aim was to examine the economic outcomes associated with long-term adherence to oral diabetes medications in the Diabetes Mellitus (DM) population. The secondary aim was to examine the economic outcomes associated with having a history of an HbA1c test during the study period. METHODS: Patients continuously enrolled from January 01, 2006 to December 31, 2011 and did not have a diabetes diagnosis or medication one year prior to the index date were eligible for inclusion in this retrospective study (N=2090). Patients who had at least two oral diabetes medication fills in the index year, had an integrated medical and pharmacy benefit, and who did not have any injectable medications during the study period were stratified to examine the primary aim (N=781). Patients were defined as adherent if they had a medication possession ratio (MPR) of greater than 80% in all five years (N=153), the remainder were classified as non-adherent (N=628). To quantify the economic outcomes associated with a history of an HbA1c test, patients were stratified based on a history of HbA1c test. RESULTS: Compared to the non-adherent group, the adherent group had lower unadjusted mean medical costs. The five-year total medical costs were $25,726 in the non-adherent group and $22,153 in the adherent group, a 16% difference (p≤ 0.05). A similar difference was observed when comparing inpatient and emergency room costs ($8694 vs. $5268, p≤ 0.001) Compared to patients without an HbA1C test during the study period (N=792), patients with an HbA1c test (N=1298) had lower total medical costs ($36,599 vs. $29,153 respectively, p≤  0.05) and inpatient and emergency room costs ($14,380  vs. $9,800 respectively, p≤ 0.05). CONCLUSIONS: Diabetes patients with consistently high medication adherence to oral medications or having a history of an HbA1c test over a five-year period had lower medical costs and lower inpatient and emergency room costs than their counterparts.