Beverley Knight stunned members of the Children in Need audience as she dropped to the floor mid-song.
However, viewers watching at home had no idea as BBC bosses edited it out.
The 43-year-old singer sang at the pre-recorded Children In Need Rocks For Terry event, celebrating the life of the late broadcaster Sir Terry Wogan, at London's Royal Albert Hall.
Hosts Greg James and Fearne Cotton introduced Beverley as "exceptional".
The show, which aired Monday, showed the Bodyguard actress performing Whitney Houston's I Will Always Love You.
In The Sun's exclusive video, Beverley can be seen leaning on a man as she was helped off stage.
A witness told The Sun: "She was singing I Will Always Love You when it happened, she just dropped to the floor.
"People came to help her really quickly and they moved onto the quiz.
"Everyone in the audience was shocked, we just hope she's feeling alright now.
"She looked extremely unwell during the show as she lolled on the floor and was helped off the stage by security staff."
A spokeperson for Beverley told The Mirror: "Bev is fine now.
"She was in a very hot dressing room back stage and left to go straight on stage where she suddenly felt faint mid-performance.
"Medics saw her backstage afterwards and said she had low blood sugar but after 30 minutes she felt much better and they signed her off to perform the number later in the evening - which she did without further issues."
The West End star later returned to the stage to sing again and it was that performance which was shown on BBC One.
Also performing at the concert were Ellie Goulding, Olly Murs, Rick Astley and a host of other music stars.