President Trump spent much of his first official Cabinet meeting of 2018 touting his administration's "tremendous" achievements in 2017.
He told them that he expects it to go well and that he would be surprised if it did not.
The president's medical examination was announced last month after he slurred part of a speech in which he declared the United States recognised Jerusalem as the capital of Israel.
Wolff wrote in his book that almost everyone who is regularly around the president is aware of his declining mental state. I'm going to open up our libel laws so when they write purposely negative and frightful and false articles, we can sue them and win lots of money, ' Trump boasted.
"Addison's disease affects your cortisol levels, your ability to handle stress", Dr. Connie Mariano, who served as White House physician for Presidents George W. Bush and Bill Clinton, told CNN in 2015. If those details are similar to those released for Obama, we will know Trump's vital statistics, including his weight, body mass index, resting heart rate and blood pressure.
Donald Trump's least presidential moments so far.
Mr Trump, on the campaign trail in 2016, repeatedly questioned whether his opponent, Hillary Clinton, possessed the mental acumen to be president.
"Actually, it was reported as incredibly good, and my performance - some of them called it a performance; I consider it work - but got great reviews by everybody other than two networks who were phenomenal for about two hours", Trump said in front of the cameras.
Famously, Trump has never smoked and drunk alcohol as his alcoholic brother Fred died aged just 43.
The four major food groups on his campaign plane were according to a book, co-authored by former campaign manager Corey Lewandowski, said to be McDonald's, Kentucky Fried Chicken, pizza and Diet Coke.
But Mr Trump as boasted of being "smart" and having "mental stability" in tweets over the past week.
Trump will be examined by the same doctor as predecessor, the report said, and a summary of the results is expected to be made public.