Justin Bieber Throws Up On Stage 2012: Vomits During 'Believe' Tour Debut, Blames it on Milk [VIDEO]

Looks like pop megastar Justin Bieber should take it easy on the lactose - during a Saturday evening concert in Glendale, AZ for the premiere of his worldwide 2012 "Believe" tour, the "Boyfriend" singer gave the Belieber crowd a little more than it had bargained for - by throwing up onstage and having to run backstage twice to continue vomiting. Even with the sudden onslaught of illness, the Biebs continued his 105-minute long set and later hit up Twitter to let fans know he's feeling fine and doesn't plan on chugging milk before hitting the stage again anytime soon.

About an hour into Saturday's show, 18-year-old Bieber had to turn his back to the crowd in the middle of performing "Out of Town Girl" in order to upchuck his lunch/dinner onto the stage floor. He quickly ran backstage to straighten himself out and returned back to a screaming crowd soon after. Not too much later, while performing "Beauty and the Beat," Biebs had to escape the stage yet again to get sick (this time out of the public's eye).

After returning to the stage for a second time, Bieber had no shame in admitting to the crowd that he had indeed just vomited, multiple times: "It's hard for me, you know, not feeling great and throwing up in front of a bunch of people. Will you love me even though I'm throwing up on stage? OK, I wanted to give you my best show ever, so do you mind if I finish it?" Beliebers had no problem forgiving the under-the-weather Bieber, and the show was an overall great success.

After the show, Bieber tweeted fans a health update - he also hinted at what exactly he thought the sudden tummy ache was caused by:

@justinbieber: "Great show. Getting better for tomorrow's show!!! Love u."

Later adding:

@justinbieber: "And... Milk was a bad choice! Lol."

The "Believe" tour continued on Sunday, Sept. 30 with a show in Las Vegas.

Another highlight of Saturday evening's "Believe" tour (not involving vomit) was Bieber dedicating his performance of "One Less Lonely Girl" to 6-year-old super fan Avalanna Routh, who passed away on Sept. 26 after a battle with a rare form of brain cancer. The Biebs tweeted:

@justinbieber: "Goodnight Avalanna. Tonight was for u. I love u."