Right-hander Jeremy Beasley has been optioned to Buffalo to make room for Gage on the active roster.
Right-handed pitcher Nate Pearson was also moved to the 60-day injured list.
Gage is 1-2 with a 1.08 ERA in 16.2 innings for Buffalo this year. The 29-year-old has not pitched in the major leagues.
Meanwhile, left-handed reliever Tim Mayza (forearm) is scheduled to have a rehab outing with Buffalo on Tuesday. If all goes well, he could be available for the Blue Jays this weekend in Detroit.
Watch the Blue Jays-Royals game on Monday night at 8:10 p.m. ET / 5:10 p.m. PT on Sportsnet ONE.