Britney has lost it.

[Not Afraid]

Poor poor girl.

Britney Spears entered rehab Tuesday after a bizarre weekend that included shaving her head and getting a new tattoo.

Spears' manager, Larry Rudolph, told People magazine's Web site that Spears, 25, had voluntarily checked herself into an undisclosed treatment facility.

"We ask that the media respect her privacy as well as those of her family and friends at this time," Rudolph was quoted as saying.

The Associated Press was attempting to reach Rudolph and other representatives for Spears.

Since she announced her separation from Kevin Federline in November, Spears, the mother of two young sons, has been seen partying with Paris Hilton, and her appearance has been increasingly sloppy.

On Friday night, Spears grabbed an electrical shaver at a San Fernando Valley salon and shaved her head completely bald.

Video on KABC-TV showed a newly shorn Spears with tiny tattoos on the back of her neck as she sat for a new tattoo — a pair of red-and-pink lips on her wrist.

Entertainment TV shows and Web sites reported Friday that she had gone in and out of rehab that week. Some reports identified the facility as Eric Clapton's Crossroads center in Antigua, in the Caribbean, but the AP wasn't able to confirm those reports.