Sharapova, who took “full responsibility” for the failed test, said she has been taking the drug legally since the age of 16, but did not realise it had subsequently been banned.
“I received a letter from the ITF that I failed a drugs test at the Australian Open,” said Sharapova. “I take full responsibility for it.
“For the past 10 years I have been given a medicine called mildronate by my family doctor and a few days ago, after I received the ITF letter, I found out that 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 legally been taking the medicine for the past 10 years.
“But on January 1st the rules had changed and meldonium became a prohibited substance which I had not known.”
Reading from a written statement that lasted for nearly three minutes, Sharapova said she was given the substance by her family doctor to deal with sickness, a deficiency in magnesium, and her family’s history of diabetes.
“I was given this medicine by my doctor for several health issues that I was having in 2006,” said Sharapova.
“Throughout my long career I have been very open and honest about many things and I take great responsibility and professionalism in my job every single day and I made a huge mistake.
“I let my fans down. I let the sport down I have been playing since the age of four and I love so deeply.
“I know with this I face consequences and I don’t want to end my career this way and I really hope I will be given another chance to play this game.”
Ahead of the news conference in Los Angeles, Sharapova’s team said there would be a “major announcement” - leading to suggestions the Russian may announce her retirement. She said: “I know many of you thought I was retiring but if I was ever going to announce my retirement it would probably not be in a downtown Los Angeles hotel with this fairly ugly carpet.”
World No 7 Sharapova has been struggling with an arm injury this year and pulled out of the upcoming Indian Wells tournament due to the injury.
The Russian said she received a letter from WADA in December to inform her of the prohibited substances for 2016, but admitted she did not look at the list. “It made me healthy and that is why I continued to take it,” Sharapova said of the banned substance after taking questions from the floor.
Asked if she knew what the consequences of her failed test may be, she said: “I do not. This is very new for me, I just received the letter a few days ago and I will be working with the ITF.”
Sharapova, the highest-paid female athlete in world sport for the last 11 years, according to Forbes, won her first grand slam as a 17-year-old at Wimbledon in 2004 and has since landed the 2006 US Open title, the 2008 Australian Open, and the French Open twice, in 2012 and 2014.
A statement from the ITF said Sharapova provided a sample during the Australian Open on January 26, and that she was charged with an anti-doping violation on March 2 after the sample tested positive for meldonium.
“As meldonium is a non-specified substance under the WADA (and, therefore, TADP) list of prohibited substances and prohibited methods, Ms Sharapova will be provisionally suspended with effect from 12 March, pending determination of the case.”