Update 11.13pm: Hillary Clinton was diagnosed with pneumonia on Friday, her doctor has revealed, after the Democratic presidential nominee abruptly left a September 11 anniversary ceremony feeling "overheated".
A video showed Ms Clinton slumping and being held up by three people as she was helped into a van after the event, and her doctor said in a statement that she had become overheated and dehydrated.
"I have just examined her and she is now rehydrated and recovering nicely," Lisa R Bardack said in a statement.
The physician said Ms Clinton has had an allergy-related cough, and during a follow-up examination on Friday she was diagnosed with pneumonia, put on antibiotics and advised to rest and modify her schedule.
Less than two months from election day, it was an unwanted image for Ms Clinton as she tries to project the strength and vigour needed for one of the world's most demanding jobs. Republican rival Donald Trump has spent months questioning her health, saying she does not have the stamina to be president.
Hillary Clinton has had to leave a 9/11 memorial service in New York before it finished after feeling "overheated".
A spokesperson for the US presidential nominee says she's "feeling much better" and is recovering at her daughter's apartment.
Clinton spokesman Nick Merrill said in a statement on Sunday that the former secretary of state attended the morning ceremony for 90 minutes in New York "to pay her respects and greet some of the families of the fallen".
He added: "During the ceremony, she felt overheated so departed to go to her daughter's apartment, and is feeling much better."
The statement offered no additional details, including whether Mrs Clinton required medical attention.