The defense secretary’s admission to Walter Reed national military medical center was announced early Sunday evening, with the Pentagon outlining his condition in a statement.
Both Republican and Democratic lawmakers criticized Austin last month for failing to disclose a cancer diagnosis and subsequent hospitalizations in December and January, including to President Joe Biden.
Some prominent Republicans, including former President Donald Trump, called for Austin to be removed from his job.
Austin apologized and is scheduled to testify before Congress on Feb. 29 about the situation.