This chapter describes the most common product categories in which dietary supplements have been found to be adulterated with active pharmaceutical ingredients (APIs) or contaminated with heavy metals. The Food and Drug Administration (FDA) established the Tainted Dietary Supplement Database from 2007 through 2021, allowing the public to identify API adulterated supplements. During that time, 1068 unique products were found to be adulterated with API. FDA approved and unapproved phosphodiesterase-5 inhibitors (sildenafil and others) are the most common commonly included APIs, in sexual enhancement dietary supplements. Sibutramine, an anti-obesity drug removed from the market due to cardiovascular adverse events, is the most included API in weight loss products although sibutramine analogues, phenolphthalein (which was removed from the US market for cancer risk), and fluoxetine can also be found. While muscle building dietary supplements were commonly adulterated before 2016, no additional adulterated products have been identified since 2017. The lack of disclosure of API circumvents clinician oversight of prescription drug use, and the use of non-FDA approved API is an important health risk for consumers. Many dietary supplements have been shown to contain heavy metal amounts above the FDA’s permitted daily exposure limit. Heavy metals can damage human organs including the brain, liver, kidneys, and bones if excessively ingested over time.