Polypharmacy is a risk factor for drug interactions (DI). Adults with intellectual and developmental disabilities (IDD) are at increased risk for polypharmacy and as such increased risk for potential DIs. The objectives of this study were to determine the number of potential DIs present in medication regimens of adults with IDD as well as factors associated with the number of potential DIs. Community-based cross sectional study. Retrospective analysis of data obtained from the cross-sectional National Core Indicators survey in the state of Oklahoma in the United States. 598 respondents were included. The number of medications prescribed, the number of potential DIs, and the association between participant factors with the total number of potential DIs present. 598 adults with IDD were studied. In this sample, over 80% had at least one DI present in their current medication regimen. There were 8.9 ± 9.7 potential DIs in the medication regimens, with 29.8% of participants having 12 or more. Greater number of medications was significantly associated with a greater number of potential drug interactions. People with IDD who take medications are exposed to potential drug interactions. Health care professionals must have clear goals and endpoints in mind when prescribing medications for this vulnerable population. Potential drug interactions are common in the medication regimens of adults with intellectual or developmental disabilities. Polypharmacy is associated with a greater number of potential drug interactions. Health care professionals must have clear goals and endpoints in mind when prescribing medications for adults with IDD to minimize the occurrence of drug interactions.