World’s fastest female marathon runner suspended over banned substance

The world’s fastest ever woman marathon runner, Kenya’s Ruth Chepng’etich, has been suspended pending an investigation into a test that found her to have tested positive for a banned substance.

Chepng’etich, who set the world on fire with her new record 2:09:56 performance at the Chicago Marathon in October, by two minutes breaching the old record, now finds herself at the center of a huge doping scandal.

As reported by the Athletics Integrity Unit (AIU), a March 14, 2025, test sample was found to contain hydrochlorothiazide (HCTZ), a diuretic that is used to treat fluid retention and high blood pressure — but is prohibited in sports because of its ability to mask other drugs.

The AIU reported that the level was 3,800 nanograms per milliliter — significantly higher than the minimum 20 ng/ml.

First, Chepng’etich willingly accepted a provisional suspension in April, which resulted in her withdrawing from the London Marathon, stating that she was “not in the right place mentally or physically.”

The AIU now formally charged her and issued its own provisional suspension, notifying her that she is at risk of a two-year ban if convicted.

For background, HCTZ is a Prohibited Substance (Class S5), and substance use is prohibited in all circumstances. Chepng’etich may still appeal and have her case heard before a Disciplinary Tribunal.

Her ascent had been stratospheric — from earning £74,500 for winning Chicago and a further £37,300 as world record earnings to racing at a record rate of 4:57.4 a mile.