Meldonium is manufactured in Latvia. It is used in Lithuania and the Russian Federation but is not approved by the United States’ Food and Drug Administration.

The five-time major champion, who is ranked No. 7 in the world, hasn’t competed since losing to Serena Williams in the Australian Open quarterfinals in January.

Sharapova, 28, announced Thursday that she was pulling out of the BNP Paribas Open at Indian Wells because of a left forearm injury. She has suffered a string of injuries in recent years, including a right leg injury that caused her to withdraw from the 2015 US Open.

Sharapova said she was taking the drug meldonium for 10 years to address a number of health issues. She said that she had been getting the flu every couple of months, had irregular EKGs and had evidence of diabetes, which runs in her family. She said that on Jan. 1, rules changed to make the drug illegal, but she was not aware.

“I take great responsibility and professionalism in my career every day. I made a huge mistake,” Sharapova said. “I let my fans down. I let my sport down.”