But despite his illness, the 19-year-old refused to stop the gig even after he puked onstage, reported Us magazine.
The 'Baby' hitmaker played the first show of his Believe world tour at the Jobing Arena in Glendale, Arizona but he shocked fans when he threw up on the stage in front of the entire audience.
The incident was caught on film and he subsequently left the stage to compose himself, asking the audience on his return, "Will you love me even tough I'm throwing up on stage?"
Bieber refused to let his ill health affect his performance and continued the show to the end as planned.
He later addressed the incident in a series of posts on Twitter, posting a picture of himself in bed, adding, "Great show. Getting better for tomorrow's show!!!! Love u (sic)... And... Milk was a bad choice! Lol (laugh out loud)."