It was not immediately clear what Kudlow's condition was.
White House chief economic adviser Larry Kudlow speaks during a television interview outside the West Wing of the White House on May 18.
Washington Post reporter Robert Costa received a statement from Kudlow's wife Judy Kudlow. "He is now in Walter Reed Medical Center".
Mr Kudlow made headlines after the G7 summit when he appeared on Sunday morning talks shows to deliver a blistering attack on Justin Trudeau, the Canadian prime minister.
For five years before his White House appointment in March, Kudlow hosted a show on CNBC on business and politics, and he's worked at the Federal Reserve Bank of NY.
"He really kind of stabbed us in the back", Kudlow said of Trudeau.
When he was a CNBC contributor before taking the White House job, Kudlow argued the metals tariffs Trump had announced would harm consumers.