Diabetes is a complicated health condition that can lead to significant health complications. Pharmacists are in an ideal position to make therapeutic interventions, provide clinical education, and can provide necessary follow-up to evaluate response to therapy for patients with diabetes. The primary objective of this study is to evaluate the mean change in hemoglobin A1c (HbA1c) in patients receiving short-term diabetes management services from a clinical pharmacist through collaborative drug therapy management. This study is a single-center retrospective chart review of patients with diabetes who have been referred by their endocrinologist to the clinical pharmacist for short-term intensification of pharmacologic management of hyperglycemia. Patients included in the study completed at least 2 visits with the pharmacist during the study period. The primary outcome was to evaluate the mean absolute change in HbA1c at 3-6 months from baseline. Data were collected from 117 patients. The average age was 55 years (19-91 years, SD ± 14.5), 65 patients (55.6%) were female, average duration of diabetes was 14.9 years (0.5-49 years, SD ± 9.9), 21 patients (17.9%) had type 1 diabetes, 96 patients (82.1%) had type 2 diabetes, and 88 patients (75.2%) had a baseline HbA1c of at least 8.5%. On average, patients reduced their HbA1c by 2.0% (P < 0.001) at 3-6 months. For patients with a baseline HbA1c of at least 8.5%, they experienced a 2.5% (P < 0.001) reduction in HbA1c at 3-6 months. The addition of a clinical pharmacist within the endocrinology practice was associated with significant improvements in glycemic control for those referred. This short-term, intensive service model demonstrates that patients can achieve significant reductions in HbA1c with temporary support from a clinical pharmacist.