The Georgia native had eight operations for chronic kidney problems throughout his time on American Idol and was scheduled to have a ninth surgery later today.
Phillips suffers from recurring kidney stones which must be removed surgically because they are too large to pass through his system.
An insider told TMZ that Tuesday's procedure will be rescheduled for early next week because Phillips has fallen ill.
Phillips apparently developed a severe sinus infection which has left the singer with a high fever.
He recently spoke out about his kidney problems in a post-victory interview.
"My right kidney just isn't kind of functioning and I need a little help with that so kind of have to get that fixed up pretty soon," Phillips said.
"I'll get surgery soon - not just quite yet, but soon. I believe I should be 100% by the time the [American Idol summer] tour starts, so I won't miss anything."
Phillips triumphed over runner-up Jessica Sanchez last week to become that latest American Idol winner.
Watch Phillip Phillips perform his American Idol winner's single 'Home' below:
Photo gallery - American Idol finale in pictures: