According to new reports, Hillary Clinton kept her pneumonia diagnosis from most of her staff, choosing to tell only family and close aides.
The Democratic presidential candidate was reportedly concerned that news of the illness would be exploited by her opponents.
Hillary Clinton was diagnosed with walking pneumonia on September 9 and advised to rest, but continued campaigning.
The candidate’s team was forced to go public with the diagnosis on September 11 when she left a 9/11 memorial early, appearing weak.
Hillary Clinton also told the broadcaster that she had not disclosed her pneumonia diagnosis, saying: “I just didn’t think it was going to be that big a deal.”
She said she had ignored a doctor’s “wise” advice to rest for five days. Hillary Clinton said she hoped to be back on the trail in “the next couple of days”.
She acknowledged she had lost her balance during 9/11 memorial, but said she did not faint.
Hillary Clinton said: “I felt dizzy and I did lose my balance for a minute, but once I got in [the van], once I could sit down, once I could cool off, once I had some water, I immediately started feeling better.”
Some critics questioned why this had only been revealed after 9/11 memorial incident and Hillary Clinton’s communications director conceded the incident had been poorly managed.
Hillary Clinton will be releasing new medical records to help ease concerns about her health, a campaign spokesman said.
Don Fowler, a former chairman of the Democratic National Committee (DNC), urged the party on September 12 to immediately come up with a process to choose a potential successor for Hillary Clinton, in case she is forced to retire with ill health.
He said he expected Hillary Clinton to fully recover but said taking precautions was necessary.
It capped a difficult weekend for Hillary Clinton, who came under attack from rival Republican Donald Trump for calling half of his supporters “deplorable” people on September 9.
On September 12, Donald Trump wished Hillary Clinton a speedy recovery. He also pledged to release the results of a medical examination he took over the past week.
Donald Trump has repeatedly suggested Hillary Clinton is unfit, telling supporters last month she “lacks the mental and physical stamina” to serve as president.