"Glee" actor Cory Monteith, who's portrayed Finn Hudson on the Fox comedy since it began in 2009, has checked into rehab.

A rep tells CNN that the 30-year-old has voluntarily entered a treatment facility for substance addiction.

"He graciously asks for your respect and privacy as he takes the necessary steps towards recovery," Monteith's rep says in a statement.

Monteith has been frank about his struggles with substance abuse, telling Parade magazine in 2011 that he began using drugs at 13, and by 19 went into rehab after his mother and friends intervened.

"I’m lucky on so many counts - I’m lucky to be alive," Monteith said at the time. "I had a serious problem."

As Monteith's present efforts at recovery have become public, his girlfriend and co-star Lea Michele is standing behind him. The 26-year-old actress, who began publicly dating Monteith in 2012, tweeted on Sunday that she's feeling "so grateful."

"I love and support Cory and will stand by him through this," she added to People magazine. "I am grateful and proud that he made this decision."

Monteith, it seems, is feeling the same gratitude.