Rihanna’s brutal tour schedule, plus reported late night partying and boozing, may be pushing the 23-year-old star to the breaking point, causing enough concern among her handlers to put her on a 24-hour health watch.

Last week Rihanna showed signs of cracking when she paused to Tweet to fans: “I’m so light-headed! WTF!!!!!.”

She was reportedly close to cancelling a show in Dublin, Ireland, Nov. 25, when she sent the Tweet, but the she went on with the show.

Now, reports that she is on a health watch, which includes around-the-clock surveillance and even has a curfew, suggests that her grueling shows aren’t the only problem.

Rihanna called off her second show in three days on Nov. 2, with her reps claiming she was suffering from exhaustion and a bout of the flu.

She tweeted a shocking photo of herself at the time, hooked up to an IV drip in a hospital in Sweden, while tweeting her apologies for canceling a show.

Tabloids overseas suggest that Rihanna was drinking heavily and partying until all hours at clubs after her shows, which would explain the health watch.

“Rihanna is running on empty but she’s still been going out drinking and living it up,” a source told London’s Sun tabloid.

She reportedly has been spotted pounding tequila shots and staying up all night to work on her new album.

The new album, Talk That Talk, hit stores late last month.

The singer has been on a 10-month, 101 day tour, and sources say Rihanna’s team is determine she look, act and perform her best for the “Loud” tour DVD she’s filming this month, according to London’s Mirror newspaper.

The paper reported that she flipped out last weekend in a tearful rant to Beyonce about being overworked.

“She doesn’t have any down time where she can completely relax. She spends most of her time in the studio, on stage or in clubs,” The Sun’s source said.

“Doctors are worried she’s overdoing it. She needs to take some time off. Otherwise she’ll be vulnerable to more illness.”

The Mirror source said Rihanna’s team is “in talks with Mariah Carey’s trainer, Patricia Gay, to fly in and start training.”

Rihanna is just one of several female pop stars who have been forced to cancel shows due to “exhaustion,” which is often a showbiz euphemism for other problems.

Lady Gaga was forced to cancel four shows in a row in 2010 during her tour after Paramedics said she was suffering from an irregular heartbeat as a result of dehydration and exhaustion.

Like Rihanna’s, her tours are also controlled by her record label.

Singing stars are under immense pressure to generate revenues for their record labels on exhaustive tours because recorded music, mainly digital downloads these days, barely make money.

Check out her photos and see her in action.

Rihanna Burns in Belfast (Click Photos to Enlarge!)