The 43-year-old singer panicked the audience at London's Royal Albert Hall when she fainted at London's Royal Albert Hal, while performing Whitney Houston's track "I Will Always Love You", reported Female First.
"She was in a very hot dressing room backstage and left to go straight onstage, where she suddenly felt faint mid performance," a source said.
The performance came to an abrupt halt and the Knight was taken off stage by paramedics.
The medical professionals later revealed that the singer was suffering from low blood sugar and after 30 minutes of monitoring, they allowed her to return to the floor to perform.