The Kenyan athlete returned an adverse analytical finding for EPO prior to her recent win at the Sydney Marathon.

Peres Jepchirchir, the Tokyo Olympic gold medallist and reigning world marathon champion, has been provisionally suspended by the Athletics Integrity Unit.

The 33-year-old tested positive for EPO [Erythropoietin] – a banned substance that stimulates red blood cell production – in an out-of-competition sample collected in Kenya before the Sydney Marathon.

Jepchirchir secured victory in Sydney with a mark of 2:18:31 on August 30, beating both compatriot Irene Chepet Cheptai (2:22:11) and Shure Demise (2:22:33).

It was the Kenyan's first race of the year after a successful 2025 season which included becoming the world marathon champion in Tokyo and recording a personal best of 2:14:43 in Valencia. That mark places Jepchirchir ninth on the marathon all-time list.

A winner of the New York City, Boston and London marathons, Jepchirchir ran a women-only world record of 2:16:16 – now bettered by Tigist Assefa's 2:15:41 – in the British capital two years ago.

Her greatest victory came at the postponed Tokyo Olympics, where she secured the gold medal in 2:27:20 ahead of Brigid Kosgei (2:27:36) and Molly Seidel (2:27:46) five years ago.

The 2016 Olympic marathon champion Jemima Sumgong is currently serving an eight-year ban after testing positive for EPO back in 2017.

The distance runner initially received a four-year ban in 2017, but two years later that was doubled to eight after claims she was injected with EPO by an “imposter” at a Kenyan hospital during a doctor’s strike were dismissed. Sumgong, who was the first Kenyan woman to win Olympic marathon gold, did not lose her Olympic title due to the timeline of the infraction.

It's a similar case for Ruth Chepngetich, who is still the world marathon record-holder, despite being banned for three years – reduced from four after an early admission – for testing positive for hydrochlorothiazide (HCTZ) – a prohibited diuretic and masking agent.

Chepngetich had an estimated concentration of 3800 ng/mL in her urine, well above the minimum reporting level of 20 ng/mL. The Kenyan stated she was taken ill two days before the positive test and had taken her housemaid’s medication as treatment, showing a photo of the medication blister pack which was marked 'hydrochlorothiazide'.

She added that she forgot to disclose this incident to the AIU investigators. Even though the standard sanction for a positive HCTZ test is a two-year ban, the AIU concluded that Chepngetich was "reckless" in taking her housemaid’s medication and that her actions equated to "indirect intent".

Chepngetich's world record of 2:09:56, set in Chicago two years ago, still stands as the achievement pre-dated the positive test from March 2025.

Jepchirchir can now request analysis of the B sample and the case will either proceed with a charge or will be closed depending on the subsequent investigation.

Gianni Demadonna, who is listed as Jepchirchir’s athlete representative by World Athletics, told NBC News via an email: "I can only say that I feel terrible about what happened and I think it’s only right that an athlete who uses the performance enhancing drugs should be disqualified."