WASHINGTON — President Donald Trump is getting his first medical checkup since taking office, a head-to-toe exam on Friday as questions swirl about the health and fitness of the oldest person ever elected to the nation’s highest office. In advance, the 71-year-old president has pushed back vigorously against suggestions he’s mentally unfit, declaring himself “a very stable genius.”

Trump raised concern last month when he slurred some words on national TV.

More questions have been raised in the weeks since, given the tone of some of his tweets and the reported comments of some of the people who deal with him day to day. Some were recently published in a new book about his first year, which Sanders denounced as “complete fantasy” for its portrayal of Trump as undisciplined, childlike and in over his head.

Trump was 70 when he was inaugurated a year ago to handle the 24/7 demands of being president.

Trump took the unusual step of threatening legal action to try to suppress publication of “Fire and Fury: Inside the Trump White House,” by Michael Wolff. He then drew even more attention to the book and the debate about his fitness with weekend tweets stating that his two greatest assets in life “have been mental stability and being, like, really smart.” Trump noted his success in business, reality TV and presidential politics, saying: “I think that would qualify as not smart, but genius ... and a very stable genius at that!”

The president is to fly by helicopter Friday afternoon to Walter Reed National Military Medical Center outside Washington in Bethesda, Md., for the exam.

There is no requirement for a president to have a physical, but modern officeholders undergo them regularly and release a doctor’s report stating that they are “fit to serve.”