The star also blamed a sick stomach, and posted a "selfie" photo on Twitter showing himself receiving intravenous fluids.
Bieber's team made no announcements Monday on whether he'll make it up to fans who paid up to $320 to see him up close. His manager Scooter Braun says Bieber managed to perform for nearly an hour against doctor's advice.
Bieber said "I'm not feeling too good, I think I'm out of energy," and apologized as he blew the audience a kiss and walked offstage with his head hung low.
