Insulin is essential for the treatment of type 1 diabetes, and most patients with type 2 diabetes will eventually require insulin for glycemic control. Several barriers contribute to delays in initiating insulin therapy in type 2 diabetes. Furthermore, insulin-treated patients often miss doses or otherwise fail to self-administer their insulin as prescribed, placing themselves at the risk of developing complications. Insulin pens can help overcome barriers to initiating insulin therapy and can facilitate the self-management of diabetes. Compared with the vial and syringe, insulin pens are more accurate, associated with greater adherence, and preferred by patients because of their convenience and ease of use. Large database analyses suggest that insulin pens may reduce the rate of occurrence of hypoglycemic events in patients with type 2 diabetes. Despite higher costs of insulin pens vs vials and syringes, studies suggest little or no increase in total health care costs and decreases in diabetes-related costs associated with reduced health care utilization with pens. Interestingly, the use of insulin pens within the United States lags far behind the use of pens in Europe and Japan. Insulin pens may be disposable or refillable, and some pens have special features [eg, audible clicks, large-dose selector and dial, memory function, half-unit dosing, high dosing (ie, 80 U)] that offer the opportunity to individualize treatment by meeting patients' needs. This review compares available insulin pens, describes strategies to facilitate their usage, and discusses how insulin pens can improve self-management of diabetes while reducing cost.