was admitted to a Los Angeles-area hospital Thursday following a TV appearance with Jay Leno.
"Last night after Selena's appearance on The Tonight Show
, she wasn't feeling well and was taken to the hospital," her rep tells PEOPLE. "She is currently undergoing routine tests."
Gomez, 18, complained of nausea and a severe headache, according to TMZ
On The Tonight Show
, where she was promoting her upcoming movie, Monte Carlo
, Leno asked Gomez about getting her driver's license and her mom meeting her boyfriend Justin Bieber
. She showed no signs of illness.
Her appearance to promote the film in Santa Monica, Calif., Friday was canceled.
Meanwhile during her taping, Bieber was at another Mavericks vs Heat game
. This time in a suite with his manager and some friends. He was also spotted chatting with Lil Wayne at halftime.
Reporting by LINDA MARX and BLAINE ZUCKERMAN