The 28-year-old Russian, a five-time grand slam champion, tested positive for meldonium, which is used to treat diabetes and low magnesium, and was only banned by the World Anti-Doping Agency as of January 1.

The ITF said Sharapova had provided an anti-doping sample at the Australian Open that had been analysed by a WADA-accredited laboratory, which returned a positive for meldonium – a prohibited substance.

“Ms Sharapova has accepted the finding of meldonium in her sample collected on January 26.

“As meldonium is a non-specified substance under the WADA list of Prohibited Substances and Prohibited Methods, Ms Sharapova will be provisionally suspended with effect from 12 March, pending determination of the case.”

Sharapova told a news conference at a Los Angeles hotel this morning she took full responsibility for it.

“For the past 10 years, I have been given a medicine called mildronate by my family doctor and it also has another name of meldonium, which I did not know.

“It is very important for you to understand that for 10 years this medicine was not on WADA’s banned list and I had been legally taking the medicine. But on January the first, the rules have changed and meldonium became a prohibited substance.”

Meldonium is used to treat chest pain and heart attacks, but some researchers have linked it to increased athletic performance and endurance. It is not approved in the United States but is available in Russia, Latvia and other countries in that region.

The stunning news came a day after Sharapova’s management team said she was going to make a “major announcement,” which had many speculating that she was going to announce her retirement from professional tennis.

I don’t want to end my career this way

“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,” said Sharapova, a teenage tennis prodigy who became the third-youngest Wimbledon champion.

“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.”

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Sharapova, who has struggled with a series of injuries in recent years, has not competed since she lost to Serena Williams in the quarter-finals of the Australian Open in January.

“I was first given this medicine by my doctor for several health issues I was having back in 2006,” said Sharapova, who according to Forbes earned $29.5 million in 2015.

“I was getting sick a lot. I was getting the flu every couple of months. I had irregular EKG results.

“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.”

-Reuters, AAP