Former tennis world No. 1 Maria Sharapova announced here Monday that she was informed by the World Anti-Doping Agency that she failed a drug test at the Australian Open in January.

Sharapova told a press conference that the test found her positive to a substance called “mildronate” she has been taking in the last 10 years for health issues.

Mildronate is also known as meldonium which is used to treat diabetes and low magnesium. It was added to the prohibited list this year.

The 28-year-old Russian tennis star was a five-time grand slam champion. She has not competed since she lost to Serena Williams in the quarter-finals of the Australian Open in January.

Sharapova said she was first given the substance back in 2006.

“I was getting sick very often and I had a deficiency in magnesium and a family history of diabetes, and there were signs of diabetes. That is one of the medications, along with others, that I received,” Sharapova said, “I know that with this I face consequences and I don’t want to end my career this way. I really hope that I will be given another chance to play this game.”

“I made a huge mistake. I let my fans down and I let the sport down. I have been playing since the age of four a sport that I love so deeply,” Sharapova also said.