Key Points Question What are the trends across adulterated dietary supplements associated with a warning released by the US Food and Drug Administration from 2007 through 2016? Findings In this quality improvement study, analysis of the US Food and Drug Administration warnings from 2007 through 2016 showed that unapproved pharmaceutical ingredients were identified in 776 dietary supplements, and these products were commonly marketed for sexual enhancement, weight loss, or muscle building. The most common adulterants were sildenafil for sexual enhancement supplements, sibutramine for weight loss supplements, and synthetic steroids or steroid-like ingredients for muscle building supplements, with 157 products (20.2%) containing more than 1 unapproved ingredient. Meaning Potentially harmful active pharmaceuticals continue to be identified in over-the-counter dietary supplements.