Alexa Ray Joel collapsed onstage during her Saturday concert at Cafe Carlyle in NYC and was rushed to the emergency room, but she will be alright.
Billy Joel and ex-wife Christie Brinkley's only daughter, 28, was diagnosed with vasovagal syncope, one of the most common causes of fainting.
"She didn't feel well all day and got sick," a source close to the singer says.
"But she wanted the show to go on. She psyched herself up to do it and then got sick onstage. It's fine. She didn't want to cancel. She's 100 percent fine."
Alexa Ray says, "I was excited and determined to fulfill my final performance, and I really wanted to end my run with a bang, but this was not what I had in mind."
"And hope I have the opportunity to make it up to the wonderful audience very soon. Thanks for all the concern," said the talented singer-songwriter.