OBJECTIVE: To identify problems faced by older adults with diabetes due to out-of-pocket medication costs. RESEARCH DESIGN AND METHODS: In this cross-sectional national survey of 875 adults with diabetes treated with hypoglycemic medication, respondents reported whether they had underused prescription medications due to cost pressures or had experienced other financial problems associated with medication costs such as forgoing basic necessities. Respondents also described their interactions with clinicians about medication costs. RESULTS: A total of 19% of respondents reported cutting back on medication use in the prior year due to cost, 11% reported cutting back on their diabetes medications, and 7% reported cutting back on their diabetes medications at least once per month. Moreover, 28% reported forgoing food or other essentials to pay medication costs, 14% increased their credit card debt, and 10% borrowed money from family or friends to pay for their prescriptions. Medication cost problems were especially common among respondents who were younger, had higher monthly out-of-pocket costs, and had no prescription drug coverage. In general, few respondents, including those reporting medication cost problems, reported that their health care providers had given them information or other assistance to address medication cost pressures. CONCLUSIONS: Out-of-pocket medication costs pose a significant burden to many adults with diabetes and contribute to decreased treatment adherence. Clinicians should actively identify patients with diabetes who are facing medication cost pressures and assist them by modifying their medication regimens, helping them understand the importance of each prescribed medication, providing information on sources of low-cost drugs, and linking patients with coverage programs.