Maria Sharapova faces suspension after testing positive for meldonium, a substance that she says she’s been taking legally for 10 years.The drug was added to the World Anti-Doping Agency's (Wada) list of banned substances on Jan. 1, 2016. Sharapova tested positive for the drug the day she lost to Serena Williams in the quarterfinals of the Australian Open, according to Sports Illustrated "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 that medicine for the past 10 years," Sharapova told BBC Sport . "But on 1 January the rules had changed and meldonium became a prohibited substance, which I had not known."The decision to ban the drug was made in September, at which point the Russian anti-doping agency sent out a memo notifying their member athletes.Meldonium is a Latvian drug that is not approved by the FDA. It’s used to treat ischaemia, a condition that limits blood flow within the body. Wada says that it found “evidence of its use by athletes with the intention of enhancing performance,” according to The Guardian Sharapova says her use has been to treat a magnesium deficiency and a family history of diabetes.“I want people to know that for 10 years Maria took this substance, which was recommended to her by her doctor after he did an extensive battery of tests to determine what medical conditions were causing her to be sick on a frequent basis,” Sharapova’s attorney John Haggerty told Sports Illustrated . “He found that she had abnormal EKG readings, that she had some diabetes indicators and when he coupled that with a family medical history of those issues, as well as low magnesium and some immune deficiencies, it was his job as her doctor to prescribe or recommend the medication that would help her be healthy.”Nike has suspended their relationship with Sharapova pending the results of the investigation.Sharapova’s camp plans to appeal for a therapeutic use exemption, which would mean she would be allowed to use meldonium. If her TUE application fails, she faces a suspension of one to two years according to BBC Sport