The Russian, 28, tested positive for meldonium, a substance she has been taking since 2006 for health issues.
Sharapova, a five-time Grand Slam champion, said she was not yet aware of the sanctions she will face.
"I failed the test and take full responsibility for that," said Sharapova, who won Wimbledon as a 17-year-old in 2004.
"I had been taking this medicine for the past 10 years, but on 1 January this became a prohibited substance which I did not know."The news conference comes days after Sharapova announced she was pulling out of the BNP Paribas Open at Indian Wells because of an arm injury. She has suffered a string of injuries in recent years, including a leg complaint that caused her to withdrawal from the US Open.
She has only played sporadically in the last eight months and hasn’t competed since losing to Serena Williams in the Australian Open quarter-finals in January.
Sharapova, who is involved in numerous business ventures off the court, is currently No7 in the WTA rankings. While a change in her plans for her playing career are a distinct possibility, Sharapova has given press conferences in the past on matters such as a launch of her confectionery brand.