London, Sep 2 - Madonna is a fitness freak but it seems age is finally taking a toll on the pop star who collapsed twice on stage during her Sticky & Sweet show in Sofia, Bulgaria.

According to thesun.co.uk, the singer lost consciousness singing 'Holiday' and had to be held up by a dancer. Then, as she left the stage during 'Spanish Lesson', she passed out and fell over.

'Madge (Madonna) was really worried backstage. She had to sit down for a longer break than usual between songs. She refused to end the show or take a break after the 'Holiday' dizzy spell. It turns out she's suffering from exhaustion. She is anaemic. She was advised to postpone the last two shows in Israel for a few days, but logistics and stubbornness stopped her. She'll do them then take some rest,' said a source.