An announcement saying the 61-year-old is in “ill health” was posted on the band’s Facebook page but no further details were provided.
“Malcolm would like to thank the group’s die-hard legions of fans worldwide for their never-ending love and support,” the statement said.
But the Rock and Roll Hall of Famers said they “will continue to make music”, despite rumours they are on the brink of retirement.
In an interview with The Daily Telegraph, frontman Brian Johnson said the group plans to meet up in Canada next month.
“We’re going to pick up some guitars, have a plonk, and see if anybody has got any tunes or ideas,” he said. “If anything happens, we’ll record it.”
AC/DC also includes drummer Phil Rudd, bassist Cliff Williams and guitarist Angus Young, Malcolm Young’s brother.
Their last studio album was 2008’s Black Ice. They released a live disc in 2012.