The band is also celebrating 20 years of 'Rise or Die Trying.'
The band were heading to their Red Rocks Ampitheatre tour date.
The LP is out January 22, and is being supported by a lengthy tour.
Kraemer cites "health" among reasons for leaving.
The compilation album features covers of Fall Out Boy's greatest hits, from "Dance, Dance," to "thnks fr th mmrs."
This announcement comes ahead of the band's upcoming Finally Outside tour, and amid potential allegations of misconduct.
