WASHINGTON — President Donald Trump is in for some poking and prodding as doctors assess whether his "incredibly good genes" continue to serve him well.

Trump was traveling to Walter Reed National Military Medical Center outside Washington on Friday for a follow-up to his first annual medical checkup as president.

His personal physician declared him to be in "excellent health" in January 2018 after a battery of tests on his heart, lungs, gastrointestinal system and other areas. Dr. Ronny Jackson, a Navy rear admiral, then presided over an extraordinary White House news conference in which he said of Trump: "He has incredibly good genes, and it's just the way God made him."

Jackson, then the president's personal physician, also predicted that Trump, who doesn't drink alcohol or smoke, will make it through his presidency with no serious medical issues.

Some questions and answers about Trump's physical exam:

Who will examine the president?

The exam will be overseen by Sean Conley, a Navy veteran and doctor of osteopathic medicine who is now the physician to the president. Jackson oversaw Trump's January 2018 exam after having done the same for President Barack Obama. The personal physician coordinates a team of doctors who rigorously examine the president. Jackson said 12 "consultants" were involved last year.

What happened to Jackson?

Jackson was replaced last year after Trump nominated him to lead the Veterans Affairs Department. Questions immediately arose about Jackson's qualifications to run government's second-largest bureaucracy. He had no significant management experience. Anonymous allegations also surfaced from current and former colleagues accusing Jackson of professional misconduct, including loosely dispensing medications and on-the-job drunkenness. Jackson denied the allegations but eventually withdrew his nomination. The Pentagon continues to investigate the allegations.

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Despite the ongoing investigation, Trump recently promoted Jackson to be an assistant to the president and chief medical adviser. In that role, the White House said Jackson will provide advice across the administration on topics including veterans' issues, the opioid crisis and health issues at the U.S.-Mexico border. Jackson will also travel and work closely with White House staff. Trump also re-nominated Jackson for a second star because of inaction by the previous Congress on an earlier nomination.

Is an exam mandatory?

No, but modern officeholders undergo them regularly and release a doctor's report assuring the public that they are fit for office.

What's included in the exam?

A lot. Last year, the public learned details about Trump's height, weight, heart rate, blood pressure and cholesterol levels. Doctors checked his eyes; ears, nose and throat; heart; lungs; gastrointestinal tract; skin; and teeth. Neurological, cognitive and stress tests were also performed. Trump's hearing was not tested; Jackson said he ran out of time. The exam stretched past four hours.

Will there be another cognitive test this year?

That's up to Trump. Jackson said he hadn't planned on giving a cognitive test last year, largely because he interacted with the president several times a day and saw no reason to. But he said Trump requested the test and achieved a perfect score. At the time, speculation had been growing about the president's mental state, based on descriptions of him in a behind-the-scenes account of the administration's early days and a public episode in which Trump slurred his words. Trump tweeted in his own defense that he is a "very stable genius."

Jackson said it is Trump's call on whether another cognitive test is performed. Questions about the president's mental state have largely subsided.

How is the president's health?

It's hard to know what, if anything, has changed, before the results of Friday's exam are made public.

Jackson's assessment last year was that Trump was in "excellent" health overall. But he added that the president, who tipped the scale at 239 pounds, would do well to drop 10 to 15 of them and shift to a low-fat, low-carb diet and take up a more defined exercise routine. Jackson said he'd work with the president (and enlist first lady Melania Trump and the president's daughter Ivanka) and the White House kitchen staff on both areas. Trump's primary form of exercise is golf. He has also said he gets lots of exercise just walking around the White House complex.

Trump's love of fast food remains, however. Last month, he invited the college football champion Clemson Tigers to the White House during the partial government shutdown. With the White House kitchen too understaffed to cater a meal for the athletes, Trump stepped in: He ordered burgers, french fries and pizza.

How will the public learn the results?

Conley is expected to release a paper statement sometime after the exam with his initial assessment of Trump's health.

Jackson released a statement some hours after last year's exam that declared Trump to be in "excellent health." Jackson then delivered — in what he said was at Trump's request — a detailed, in-person readout the following week in which he spent about an hour answering questions from reporters in the White House briefing room.