The alternative rock greats had been due to headline Saturday’s annual Weenie Roast concert held by radio station KROQ near the band’s native Los Angeles.
But the band took the stage without their instruments as bassist Flea apologetically told the crowd that Kiedis was on his way to the hospital due to stomach pains.
“We are unable to play tonight. We will be playing for you very soon and we will play for you like the feral animals full of love that we are,” Flea said, according to video footage posted by a spectator.
“We are so sorry,” added Flea, appearing topless as is often his wont.
Weezer, another band that built a following during the 1990s alternative rock boom, instead became the headliner of the concert.
The Chili Peppers in a statement Sunday explained that Kiedis had been hospitalized for “complications from the intestinal flu” and was “expected to make a full recovery soon.”
The band, however, canceled its next show which was scheduled for Tuesday in Los Angeles.
The Red Hot Chili Peppers have an active touring schedule ahead of them as they prepare to release “The Getaway,” their first album in five years, on June 17.
Upcoming dates including appearances at major international festivals including Japan’s Fuji Rock, Roskilde in Denmark, Reading and Leeds in Britain and the 25th anniversary of Lollapalooza in Chicago.
The Chili Peppers rose to fame in the late 1980s as they brought an element of funk, especially through Flea’s distinctive bass, to hard rock, with lyricism by Kiedis that ranged from dark tales of drug use to the ironic.