Insulin therapy is crucial to the treatment of many patients with diabetes mellitus. Therefore, it is important for pharmacists to consider the clinical and economic implications of the decision between insulin pens and insulin vials and syringes. Clinically, insulin pens show an advantage through improved adherence and reduced hypoglycemic events. Furthermore, overall health care costs were either unchanged or improved in insulin pen users as compared with those using insulin vials and syringes, although little economic advantage was observed when switching from insulin vials to insulin pens. Patients tend to prefer insulin pen use based on patient satisfaction and ease of use. Through an understanding of the advantages and disadvantages of insulin pens and vials and syringes, pharmacists can help to advocate for the most appropriate insulin-delivery method to maximize clinical outcomes and to reduce overall health care spending.