A statement released by the office of the commissioner said Friday that Ramirez had recently been told of "of an issue under Major League Baseball's joint drug prevention and treatment program."
"Rather than continue with the process under the program, Ramirez has informed MLB that he is retiring as an active player," the release said. "If Ramirez seeks reinstatement in the future, the process under the drug program will be completed. MLB will not have any further comment on this matter."
Ramirez was suspended for 50 games while playing for the Los Angeles Dodgers in 2009 for testing positive under the drug policy. Although details of the failed test were not revealed, Ramirez said it involved a prescription drug that was included on the banned list.
Ramirez signed a one-year, $2 million contract with Tampa Bay prior to this season. He had one hit in 17 at-bats during Tampa Bay's first five games.
"We are obviously surprised and disappointed by this news," a release issued by the Rays said. "We will have no further comment on this matter, and our fans and organization will carry on."
Ramirez spent most of his 18-year major league career with Boston, where he signed an eight-year, $160 million contract in 2000. He helped the Red Sox win a World Series title in 2004.