Sanjay Gupta challenged the credentials of Donald Trump's personal physician after questioning language the doctor used to promote the presidential candidate's health and vitality.

The CNN medical correspondent appeared Tuesday morning on "New Day" to explain some of his findings after digging into the background of Dr. Harold Bornstein, who announced last year by letter that Trump would "be the healthiest individual ever elected to the presidency."

"He's been a doctor with Trump for 36 years, between him and his father," Gupta told CNN's Chris Cuomo. "He says he's a fellow of the American College of Gastroenterology, so a GI doc. Interestingly, we called that particular organization (and) they said he was a member -- but he hasn't been a member there in over 20 years, since '95 now."

Trump announced the letter, which he offered in lieu of medical records, on Twitter by saying it had been issued by Dr. Jacob Bornstein -- Harold's father, who died in 2010 at age 93.

Questions about the 70-year-old Republican candidate's own health have been raised as he and his surrogates suggest Hillary Clinton might be suffering from a variety of serious ailments.

Gupta took another look at the letter Trump offered in December and found it odd that the doctor used "positive" as a synonym for normal and relied on hyperbolic language.

He also found that the younger Bornstein might have exaggerated his credentials in the letter.

"In fact, the hospital, Lenox Hill Hospital, says he's part of the section of gastroenterology -- he's not actually a member of that section," Gupta explained. "He does have admitting privileges at the hospital but he's not (part of that section)."

"So there are some things in the letter with regard to his qualifications that are a little bit questionable," Gupta continued. "Really, it was more, sort of, the language of this letter that I thought was quite surprising. It wasn't written the way that many typical medical letters are written."