The carelessness of national athletes in consuming the wrong supplements caused them to be embroiled in doping issues, said National Sports Council (NSC) director-general Datuk Ahmad Shapawi Ismail.

He said they had been given complete information on prohibited supplements as they contained banned substances which could lead to failing a doping test.

"Whatever new products introduced or given to them should be referred to the National Sports Institute earlier, to ensure they do not contain banned substances.

"We have advised athletes on the matter and doping cases among athletes were due to their own negligence and they should be held responsible over the matter," he told a media conference at the Kedah Sports Transformation Convention Monday.

Ahmad said NSC had tirelessly briefed all athletes on doping so that they exercised care when taking supplements or any other substances.

Meanwhile, the convention opened by state youth and sports executive committee chairman Aminuddin Omar was attended by 38 sports associations in Kedah, aimed at producing quality athletes in future.