The five-time Grand Slam winner said that she had been taking meldonium, or mildronate as she knew it, since 2006 in order to help her deal with a number of health issues such as getting sick with influenza often, irregular electrocardiogram (ECG) results and even signs of diabetes.

Sharapova pointed out that she was not aware that the substance was included in WADA’s list of banned drugs earlier this year and was informed by the International Tennis Federation (ITF) about the matter through a letter she received last week.

She said that she does not know what possible disciplinary action she would have to face as a result of the finding.

According to the ITF, Sharapova is set to receive a provisional suspension from participating in tournaments while the doping case is still being finalized. Depending on whether she had made an honest mistake or she willfully took the banned drug for the purpose of cheating, she could face minimal action from the tennis federation or a multi-year ban.

“I made a huge mistake,” Sharapova said. “I let my fans down. I let the sport down that I’ve been playing since the age of 4 that I love so deeply.”

Meldonium

Meldonium is an anti-ischemic drug developed by researchers at the Latvian Institute of Organic Synthesis (OSI) and is currently being made and marketed by the Riga-based drug company AS Grindeks.

It is primarily used to prevent the development of ischemia, a condition known that severely restricts the flow of blood to different tissues in the body. It is also used by doctors to treat patients with brain circulation disorders.

People who take meldonium often experience an improvement in their mood, allowing them to live a more active lifestyle, according to the National Library of Medicine. However, the use of the drug was banned, particularly for athletes, because it enhances the endurance and oxygen uptake of the body.

WADA decided to add the drug to its list of banned substances in September 2015, which took effect at the start of 2016. The group classified meldonium as an S4 substance, referring to the drug as a hormone or metabolic modulator.

Russia’s anti-doping agency sent out a memo to its athletes about WADA’s ban on the use of meldonium in September.

Aside from Sharapova, other athletes who tested positive for meldonium use include former European ice dancing champion and Olympic gold medalist Ekaterina Bobrova, Russian cyclist Eduard Vorganov and former world champion in 1,500-meter running Abeba Aregawi.