Carola's shaky performance at Friday's dress rehearsal raised the question as to whether she would be in good enough shape to reach the high notes in her song Evighet on Saturday night.
Tabloid Aftonbladet reports that the star has been banned from speaking by her doctors, and is receiving support from her spiritual adviser Andreas Nielsen.
Manager Ulrika Hammar told Expressen that she needs to save her voice until Saturday's final at the Globen arena in Stockholm.
"She's met a singing coach who says she needs to be quiet and rest," he said.
Prior to the rehearsal, the singer wrote on her blog that "it feels that I have planted two potatoes between my vocal cords."
But the evangelical Christian added that she was ready to "start warming up and really drawing on heaven."
Competitors in Saturday night's competition poured cold water on Carola's claims to have voice problems. Jacob Samuel, singer in the Poodles said, "I hate it when singers go on and talk about illnesses. They're traditionally hypochondriacs."
Bookmakers Ladbrokes stopped all bets on the Melodifestivalen result on Wednesday after a huge number of bets on Carola.
But the singer's troubles have caused some to speculate that Alexander Bard's band Bodies Without Organs could snatch victory from under her nose.
The Melodifestivalen final will be shown on SVT1 on Saturday at 8pm, and repeated on Monday at 12.05pm