Pop star Lady Gaga cancelled a concert in Indiana on Thursday after she "passed out" and had difficulty breathing, she said on Twitter.
The gig has been rescheduled for January 26., the 23-year-old added.
"I've been crying for hours, I feel like I let my fans down 2nite," she wrote on social messaging site Twitter late on Thursday. "An hour before the show, I was feeling dizzy and having trouble breathing.
"Paramedics came to take care of me, and told me my heart-rate was irregular -- a result of exhaustion and dehydration."
The flamboyant pop star, one of the top-selling artists of the last two years with hits "Just Dance" and "Poker Face", apologized to fans.
"I am so devastated. I have performed with the flu, a cold, strep throat: I would never cancel a show just based on discomfort."
According to her website, she is next scheduled to perform at a concert in Atlantic City on Saturday.