Conor McGregor, the Ultimate Fighting Championship (UFC) star, reportedly continued using banned performance-enhancing drugs even after recovering from a severe leg injury sustained in 2021. While McGregor and his team have defended the drug use as medically necessary to aid healing, two individuals familiar with the matter indicated that the fighter used anabolic steroids and human growth hormone well beyond his recovery period.

Officials with the UFC learned from McGregor that he remained on the substances partly because of the effects they had on his energy and overall feeling, according to the sources who spoke on condition of anonymity due to confidentiality concerns. McGregor, now 37, had been outside UFC’s drug-testing program for more than two years following his injury, a period during which he reportedly took the banned substances. Experts in anti-doping have criticized this move, suggesting it exposed a loophole allowing McGregor to avoid suspension despite drug use.

Testing resumed for McGregor in October 2023. During the subsequent period, he was subjected to multiple tests, including 15 in 2026. UFC officials said all samples collected over the past two years—totaling 32 samples—were negative for banned substances. However, in October 2025, the UFC suspended him for 18 months after missing three drug tests, a suspension that has since expired.

McGregor’s injury occurred during a July 2021 fight when he suffered a significant fracture in his left leg. The surgery was performed by Neal ElAttrache, a well-known sports physician affiliated with major league baseball teams. While ElAttrache did not prescribe the banned drugs himself, he is reported to have supported McGregor’s use and even wrote a letter endorsing a therapeutic use exemption (TUE) request submitted to the United States Anti-Doping Agency (USADA), which oversees UFC drug testing. That exemption was ultimately denied.

The human growth hormone and anabolic steroids prescribed to McGregor were intended to accelerate bone healing, but federal law restricts prescriptions of human growth hormone to specific conditions such as certain height deficiencies and HIV-related wasting syndrome. Experts note that prescribing the drug for fracture recovery falls outside legal FDA-approved guidelines. Physicians who issue human growth hormone prescriptions for unapproved uses risk felony charges, though prosecutions are rare.

Medical and anti-doping experts have expressed concerns about McGregor's use of these substances beyond the rehabilitation phase. April Henning, an anti-doping expert from Heriot-Watt University, described the situation as a violation of fair competition, emphasizing the potential ongoing advantage McGregor could have over opponents. Keith Baar, a professor of molecular exercise physiology at the University of California, Davis, noted that such substances can induce long-lasting physiological changes, with animal studies showing benefits extending well beyond the period of active administration. He also highlighted the risks, including cardiovascular problems and organ enlargement.

McGregor has publicly stated that he took extraordinary measures to ensure he could walk and function normally after his injury. Specialists who worked with him reportedly advised a short course of the drugs for healing purposes, although McGregor’s use apparently extended over a longer timeframe.

The UFC reaffirmed that McGregor had adhered to the rules of its comprehensive drug program since resuming testing and emphasized that he has not competed for five years. Meanwhile, questions persist about the legality and ethics of McGregor’s prolonged use of banned drugs and the medical endorsements that supported him.