The World Anti-Doping Agency's 2026 Prohibited List was approved by its Executive Committee in September 2025 and took effect on 1 January 2026. WADA characterised the year's changes as mostly clarifications rather than wholesale additions.
Within the anabolic agents category (S1), WADA amended the wording to state explicitly that prohibited anabolic agents are banned 'including their esters.' An ester is a chemical modification that changes how long a compound stays active in the body; common testosterone esters include cypionate and propionate. The clarification confirms that esterified forms are covered even though they cleave to the same parent steroid.
A more substantive addition is the listing of non-diagnostic use of carbon monoxide as a prohibited method (section M1.4), because CO inhalation can stimulate red-blood-cell production. Controlled diagnostic uses, such as CO-rebreathing measurement of total haemoglobin mass or lung diffusion testing, remain permitted.
WADA also added illustrative examples across other classes, including peptide hormones and metabolic modulators. The full list and summary of modifications are published on WADA's website.