Former Olympic champion Dawn Harper-Nelson has been banned for three months after testing positive for a banned diuretic.
The American, 32, said she was given hydrochlorothiazide for high blood pressure but failed “to fully understand how its administration was governed by current doping protocols”.
Harper-Nelson won 100m hurdles gold at Beijing 2008 and silver at London 2012.
Diuretics increase urine production, but are not performance enhancing.
However they can be used to mask the presence of other illegal substances or promote weight loss.
“I have learned a valuable lesson and hope my mistake will serve as a reminder to all athletes to be diligent in thoroughly checking any and all prescribed medications,” Herper -Nelson added.
Her ban has been in place since 1 December.