Credit: GSI Media

Feeling better?

Selena Gomez paid another visit to an L.A. hospital on Saturday. The 18-year-old singer and actress stayed at a facility overnight on Thursday following an appearance on The Tonight Show; Gomez had reportedly complained of nausea and a severe headache, and underwent routine tests to diagnose what went wrong.

One insider tells Us Weekly that Justin Bieber's love collapsed from food poisoning coupled with exhaustion. But before her hospital stay, "Selena was nothing but professional" at the Tonight Show, another insider says.

"She did a backstage interview and hung out with Jim Carrey after the show. The Tonight Show people didn't even know she wasn't feeling well."

But the Monte Carlo star is set to perform for fans on Monday at Santa Monica Place -- kicking off her 10-city tour -- in a show rescheduled from Friday.