The actress, 24, who most recently spent 23 days in a live-in program at UCLA Medical Center, planned to "step up her treatment" and "do more" than previously expected, a source has said.
The name of the new program wasn't immediately known, although it's in Southern California, according to the source. She checked in late Monday.
Lohan was released from a Lynwood, Calif., jail Sept. 24 after winning an appeal to be granted bail following a failed drug test. She is now wearing an alcohol-detecting ankle bracelet.
Reporting by KEN LEE