AbstractBACKGROUNDFish oil supplements have grown in popularity in recent years owing to their multiple health benefits, leading to rapid growth in the number of fish oil supplements available for consumers. When choosing a product, it is important that label claims for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are met, especially when a specific dosage is required. In this study the amounts of EPA and DHA in 16 of the top‐selling liquid fish oil products from the American marketplace were analysed and compared with their label claims. Peroxide value, a measure of oxidation, was also determined, along with lipid class.RESULTSThis study found that over half of the supplements did not meet their label claims for EPA and DHA, and a quarter exceeded recommended limits for peroxide value.CONCLUSIONThese results suggest that more stringent regulation is required for fish oil products. © 2012 Society of Chemical Industry