Extreme caution is recommended regarding supplement use. A number of positive tests have been attributed to the misuse of supplements, poor labeling or contamination of dietary supplements.

The use of dietary supplements by athletes is a concern because in many countries the manufacturing and labeling of supplements may not follow strict rules, which may lead to a supplement containing an undeclared substance that is prohibited under anti-doping regulations. Taking a poorly labeled dietary supplement is not an adequate defense in a doping hearing.

Neither WADA nor WT is involved in any supplement certification process and therefore do not certify or endorse manufacturers or their products. WADA and WT do not control the quality or the claims of the supplements industry.