Machado originally was suspended June 10 for intentionally throwing his bat on the field during an at-bat in Baltimore's game against Oakland on June 8. Machado appealed the suspension. The appeal was heard Wednesday, and the five-game suspension was upheld.
The Orioles will be forced to play Monday with a 24-man roster.
Machado tossed his bat in the direction of third base during a plate appearance in which Oakland reliever Fernando Abad threw successive high-and-tight pitches. After the bat went soaring, both benches emptied. Machado and Abad were ejected.
Two days earlier, Machado yelled in the face of Oakland's Josh Donaldson after the third baseman tagged him on the chest and knocked him over.