Olympic champion Sun Yang wins his favored 1,500m freestyle event at the Chinese National Swimming Championships, clocking 14 minutes 54.52 seconds, in Huangshan, Anhui province, Oct 14, 2014. [Photo/IC]

BEIJING - Chinese multi-Olympic and world swimming champion Sun Yang had failed a doping test and been banned for three months, China Anti-Doping Agency (CHINADA) told Xinhua on Monday.

Sun tested positive for stimulant trimetazidine in an in-competition doping test on May 17 during the national swimming championships.

Sun gave up the chance to have the B sample tested but defended himself in a July hearing where the experts decided to hand him a three-month ban.

Sun said he used the drug for medical reasons and had been unaware that it was listed in WADA's 2014 prohibited list. Trimetazidine is able to increase coronary flow reserve and was added to the prohibited list in January 2014.