The 21-year-old 'Wrecking Ball' singer was not able to perform in Kansas City as scheduled, reported Ace Showbiz.
"Cyrus has been hospitalised for a severe allergic reaction to antibiotics and has been placed on medical rest by her doctors," a statement from Kansas City's Sprint Center read.
No replacement date has been announced yet.
Cyrus herself tweeted an apology to fans for cancelling the concert.
"Kansas, I promise I am as heartbroken as you are. I wanted to badly to be there tonight... Not being with you all makes me feel worse than I already do," Cyrus wrote.
She also posted a photo of her on hospital bed holding a toy octopus.
"Mr Octopussy & some amazing Drs are taking good care of me," she captioned.
Cyrus has been ill in the past few days. She has also cancelled her concert in Charlotte due to flu.