As it turns out, milk doesn't always do a body good.
Justin Bieber had a bit of an accident when he kicked off his "Believe" tour in Glendale, Ariz., Saturday night after consuming the beverage before the show.
The 18-year-old pop star was in the midst of performing "Out of Town Girl" when he suddenly turned around, threw up on stage and ran off.
The Biebs returned quickly, however, telling the crowd "I'm sorry, I'm going to slow things down," according to USA Today, and played the ballad "Fall" on an acoustic guitar.
But that wasn't the end of Bieber's tummy troubles.
A little later in the gig, while performing "Beauty and a Beat," the superstar singer ran off stage again, stopping the show abruptly for a few minutes.
"It's hard for me, you know, not feeling great and throwing up in front of a bunch of people," Bieber said to a screaming crowd upon his return. "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?"
And that he did, dedicating "One Less Lonely Girl" to his late fan Avalanna Routh, who passed away from cancer Wednesday.
"Great show. Getting better for tomorrow's show!!!! Love u," Bieber tweeted, along with an instagram pic of himself laying in bed. "And .... Milk was a bad choice! Lol. Goodnight Avalanna. Tonight was for u. I love u."
Jon M. Chu, creative director of Bieber's tour, told E! News exclusively that Bieber powered through show impressively despite his condition.
"The star of the show last night was Bieber, the ultimate professional," Chu said. "And he really impressed me with his honesty to his fans, without hesitation. This guy knows his audience more than anyone."
Chu said the night was very emotional, adding, "And when he told the audience he was not choosing a "one less lonely girl" tonight and instead singing it to Avalanna and sang it to an empty chair with a flower crown on it...The whole audience was bawling. Including me. I don't think I've ever felt that emotional at a concert before."
—Additional reporting by Ken Baker