The short answer to the question following Serena Williams around her comeback is no. The class of medication the 23-time Grand Slam champion has said she uses is not prohibited under tennis anti-doping rules, and never has been. The longer answer is that tennis knows the rule may not stay that way, and the sport’s integrity chief said as much on Sunday.
Karen Moorhouse, chief executive of the International Tennis Integrity Agency, was asked about weight-loss drugs on the “Off Court with Greg Rusedski” podcast and pointed the question upward. The ITIA administers the anti-doping program across professional tennis but does not decide what goes on the banned list. That is the World Anti-Doping Agency’s job, and Moorhouse said tennis would follow WADA’s lead and its scientific expertise on whether the drugs offer a competitive benefit. She called it a genuinely interesting area and said it was right that WADA is examining it.
What Williams has actually disclosed matters here, because the specifics have been blurred in circulation. In an August 2025 interview timed to a paid partnership with the telehealth company Ro, Williams said she had lost 31 pounds using a GLP-1 receptor agonist after struggling to reach a healthy weight following the births of her two daughters. She has consistently declined to name a brand. Her husband, Reddit co-founder Alexis Ohanian, is an investor in Ro and sits on its board. Several outlets have since named a specific product; none of those attributions trace back to Williams herself.
Under the 2026 WADA Prohibited List, GLP-1 receptor agonists are not banned, in or out of competition, and no therapeutic use exemption is required to take them. They sit one tier below that, on WADA’s Monitoring Program, which tracks substances that are not prohibited but are being watched for patterns of misuse. Markers of semaglutide have been monitored since 2024; from Jan. 1, 2026, markers of tirzepatide were added, monitored both in and out of competition.
Monitoring carries no sanction. It is a data-gathering step, and substances typically sit there for several years before WADA either prohibits them or drops them. For a substance to be added to the list, WADA requires it to meet at least two of three criteria: performance enhancement, health risk, or a violation of the spirit of sport.
The ADHD question that surfaced in the same interview is governed by an entirely separate rule, and the two should not be run together. Stimulants prescribed for attention-deficit/hyperactivity disorder, including methylphenidate, are prohibited in competition and do require a therapeutic use exemption. Moorhouse pushed back firmly on a perception she said circulates within the sport, that large numbers of players hold such exemptions, calling it flatly untrue and noting that an ADHD exemption requires two independent experts to confirm the diagnosis before the ITIA’s TUE committee will consider it.
The most-cited case remains Fernando Verdasco, the former world No. 7, who accepted a two-month voluntary provisional suspension in 2022 after testing positive for methylphenidate, having let his exemption lapse. There is no public indication that Williams has ever taken ADHD medication or applied for an exemption for one. The subjects converged in a podcast, not in her file.
Williams has her own recent history with the machinery. She re-entered the ITIA registered testing pool in October, denied a comeback was coming, then completed the mandatory six months of out-of-competition availability and became eligible to compete again on Feb. 22. Ahead of Wimbledon she described the whereabouts system as grueling and unprofessional, objecting that a missed test outside her designated hour can still count against her.
For an American audience, the stakes are at Flushing Meadows. Williams played doubles at Berlin and Queen’s Club in June, lost her Wimbledon opener to Maya Joint on June 30, then withdrew from doubles with Venus with a knee problem. She does not appear in the fields for Washington, Montreal or Cincinnati. Coach Rennae Stubbs has said the intention is the US Open if the body holds up. The rulebook, for now, poses no obstacle.
