Chinese swim star Sun Yang failed a drug test in May and served a three-month suspension that ended before he competed at the Asian Games in September.
Chinese officials did not make public the failed test and suspension until Monday.
They said he tested positive for the banned stimulant trimetazidine on May 17 during the Chinese National Championships.
Sun said he used the prescription drug Vasorel for a heart condition he’s had since 2008, according to Xinhua News Agency. He said he was unaware that trimetazidine, a substance in the prescription drug, was added to WADA’s prohibited list this year.
He could have been allowed to legally use the substance had he filed a therapeutic use exemption with doping officials, since it was for a medical condition.
“I have been tested numerous times during years of training and competition, and I had never failed one before,” Sun said, according to Xinhua. “I was shocked and depressed at that time, but at the same time it made me cherish my sporting life even more. I will take it as a lesson and be more careful in the future.”
Sun was given a reduced three-month ban because he “proved with sufficient evidence that he did not intend to cheat,” Zhao Jia, deputy director of CHINADA, said, according to Xinhua.
Sun, 22, won four medals at the London 2012 Olympics, including gold in the 400m and 1500m freestyles. He swept the 400m, 800m and 1500m frees at the 2013 World Championships, where he was named the male swimmer of the meet by swimming’s international governing body.
Sun was stripped of his 1500m national title and fined about $816, according to Xinhua.