The Heat have listed Lowry out for Monday night's game against the visiting Raptors for personal reasons.
It would have been Lowry's first game against his former team since he was acquired by Miami this past off-season.
The Raptors are scheduled to play in Miami again on Jan. 29. The Heat are slated to play in Toronto on Feb. 1, but there could potentially be no fans at that game if the Ontario government decides to extend its COVID-19 regulations around capacity limits at large events.
Miami's Bam Adebayo, who was expected to return on Monday from thumb surgery that has kept him out six weeks, is also listed as questionable.
Adebayo was averaging 18.7 points and 10.2 rebounds before his thumb injury.