Russian tennis champion Maria Sharapova, ranked seventh internationally, confessed to taking the drug meldonium during the 2016 Australian Tennis Open, after she tested positive for the prohibited substance.

The drug has been banned by the World Anti-Doping Agency since January. The International Tennis Federation announced that Sharapova will be suspended beginning 12 March 2016.

Sharapova, who ranked first internationally in August 2005, said she made a huge mistake. However she said her excuse was that she was using this substance due to health issues since 2006.

US multinational Nike, one of the player’s most prominent sponsors, suspended its sponsorship of the player during the period of investigations.