As reported by AOL Music Blog, Rihanna has been powering through her demanding Loud tour concert schedule, despite multiple recent health scares -- including bouts with the flu and exhaustion. But over the weekend (Dec. 17), RiRi's health troubles came to a head, causing the singer to run off stage to throw up during her show in Lisbon, Portugal.

As Rihanna performed to a sold-out crowd at Lisbon's Atlantico Arena in Portugal, she confused fans after suddenly running off stage in the middle of her hit 'What's My Name?' After the show, she took to her Twitter page to explain the interruption to her fans.

"Portugal tonight was legendary!!! I ran off stage to throw up, halfway thru What's My Name ... made it back juuuust in time for Rude Boy."

The mid-show vomiting session is the latest in a string of health-related incidents for the pop star. Her health woes started at the end of October when she was rushed to an emergency room in Sweden and was forced to cancel a number of shows while she battled the flu.

Upon her release from hospital, Ri's doctors advised her to seriously cut back on her hard partying ways in order to regain her health.

By early December, RiRi reportedly suffered a backstage meltdown after complaining about being "so light-headed" on Twitter. The singer was subsequently put on 24-hour health watch by her label. Since then, the tired and troubled star has reportedly reached out to music industry vet Beyonce for advice on how to cope with her hectic schedule and the toll it was taking on her health.

Watch Rihanna Run Off Stage at 1:55

Watch 'Rihanna Reportedly on 24-Hour Health Watch'