Leaked e-mails show concerns about Mrs Clinton's health as early as last year
Donald Trump has revealed details of his most recent health report on a US TV show - but the encounter will not be screened until Thursday.
The Republican Party's presidential nominee appeared on 'The Dr Oz Show' for what his campaign team described as a chat about his general well-being and his family's medical history.
Mr Trump also handed the show's host Mehmet Oz a one-page summary containing results from his most recent physical exam.
The exam was conducted by his physician Dr Harold Bornstein last week and Mr Trump's campaign said they would not disclose the results yet.
A statement from the show said Dr Oz took Mr Trump "through a full review," looking at his nervous system, cardiovascular health, prostate health and family medical history.
The appearance comes amid growing pressure on both Mr Trump and his Democratic Party rival Hillary Clinton over their health.
Mr Trump's TV appearance will air on the day Mrs Clinton is due to return to the campaign trail after appearing to buckle after a 9/11 memorial ceremony.
It was later revealed that she had been diagnosed with pneumonia and she admitted going against her doctor's advice to rest.
Leaked e-mails from former US secretary of state and retired general Colin Powell revealed he had concerns about Mrs Clinton's health as early as March last year.
According to a leaked e-mail conversation between him and one of the Democratic Party's biggest donors Jeffrey Leeds, Mr Powell said he thought Mrs Clinton was "working herself to death".
He wrote: "On HD tv she doesn't look good.
"After speaking at the UN and doing the crummy press conference she flew to SF to go do a paid gig for EBay and then went to Marc's house to get ready for a money dinner for the Clinton Foundation.
"I was in Marc's second house behind it and ducked her so we didn't turn loose another email story by being seen together. She then flew back east the next morning.
"She will turn 70 her first year in office."
The reply from Mr Leeds was: "Sheldon Whitehouse, who is a huge Clinton supporter (and Democratic senator), said they were both giving speeches at the same event a few months back and she could barely climb the podium steps."
The e-mail conversation is among many others obtained by the DC Leaks website and first published by Buzzfeed.
In other e-mails, Mr Powell slams Mr Trump, describing him as a "national disgrace" and an "international pariah" who "appeals to the worst angels of the GOP nature and poor white folks".
Mr Powell, secretary of state from 2001 until 2005, confirmed to NBC that the leaked messages were authentic and that those who hacked into his e-mails were in possession of "a lot more".