(CNN) -- Doctors ordered Miley Cyrus to stay in a Kansas City hospital a second day after she suffered "a severe allergic reaction to antibiotics," the singer tweeted Wednesday.
"Im so sorry but somethings are outta my control," Cyrus said in a tweet apparently sent from her hospital bed Wednesday.
Cyrus, 21, told fans she would have to cancel her "Bangerz" tour concert at the Scottrade Center in St. Louis set for Wednesday night.
"I can't get a hold of my team because it is so early so I want to be the one to tell my fans especially the ones trekking to get there(tbc)" one tweet said.
Cyrus also tweeted what appeared to be a reaction to reports that her hospitalization was related to something other than her recent bout with the flu. "humans can b so selfish. if any1 thinks id rather b layin n a hospital bed than doing what i love on stage theyre f--kin LAME. Miserable"
Her Tuesday night concert at the Sprint Center in Kansas City, Missouri, was canceled when she was hospitalized that afternoon, according to a statement from the arena.
"Cyrus has been hospitalized for a severe allergic reaction to antibiotics and has been placed on medical rest by her doctors," the statement said. "She will not be able to perform as scheduled."
The singer was not too ill to tweet from her Kansas City hospital bed, though.
"Kansas I promise Im as (heartbroken) as you are. I wanted so badly 2 b there 2night. Not being with yall makes me feel s--ttier than I already do," she wrote in a Twitter message to fans Tuesday afternoon.
"Mr. Octopussy & some amazing Drs are taking good care of me," Cyrus wrote in tweet that included a photo of her in a hospital bed wearing a gown. She was holding a green octopus toy in front of her face.
Cyrus fell ill with the flu earlier this month, causing the cancellation of a concert in Charlotte, North Carolina.
CNN's Carolyn Sung and Matthew Stucker contributed to this report.