HILLARY Clinton has been diagnosed with pneumonia, doctors have revealed in a statement that sheds new light on her near-collapse after a September 11 commemoration ceremony on Sunday.

The presidential hopeful’s “medical episode” has reignited the questions about her health, which were first raised by Donald Trump and his supporters.

Dr Lisa Bardack said in the statement that Clinton had been experiencing a “cough related to allergies” and was diagnosed with pneumonia on Friday.

Clinton was given antibiotics and advised to rest and modify her schedule, but she became “overheated and dehydrated” at a September 11 memorial service in New York, Dr Bardack said.

“I have just examined her and she is now rehydrated and recovering nicely,” she said.

The Democratic presidential candidate left the commemoration ceremony on the 15th anniversary of 9/11 on Sunday morning after just an hour-and-a-half. According to sources, she nearly fainted shortly before a moment of silence during the event at Ground Zero.

A witness told the New York Post the former secretary of state’s knees buckled and she lost a shoe as her aides led her away from the crowds.

Video soon surfaced showing the 68-year-old losing her balance as she waited with her team for a car near the World Trade Centre. Clinton’s security detail had to help her into the black van before she was driven to her daughter Chelsea’s Manhattan apartment nearby.

Hillary Clinton 9/11 NYC pic.twitter.com/q9YnsjTxss — Zdenek Gazda (@zgazda66) September 11, 2016

“Secretary Clinton attended the September 11th Commemoration Ceremony for just an hour and thirty minutes this morning to pay her respects and greet some of the families of the fallen,” spokesman Nick Merrill said after the incident. “During the ceremony, she felt overheated, so departed to go to her daughter’s apartment and is feeling much better.”

Earlier, Clinton was photographed in the crowd at Ground Zero alongside New York City Mayor Bill de Blasio and US Senator Chuck Schumer. She was the only person wearing dark sunglasses during the overcast morning. The temperature was around 27C.

Clinton has been dogged by accusations of poor health for months now, with Republican candidate Donald Trump and his top surrogates claiming she does not have the “mental and physical stamina” to be president.

She brushed off concerns about her poor health during an appearance on Jimmy Kimmel Live last month, calling Trump’s accusations a “wacky strategy” against her.

Last week, Clinton suffered a two-minute coughing fit during a campaign event in Cleveland, Ohio which she blamed on seasonal allergies — and her rival.

“I’ve been talking so much. Every time I think about Trump I get allergic,” she joked in front of the crowd.

Trump seized the opportunity to cast doubt over Clinton’s health again, tweeting, “What’s up?”

Mainstream media never covered Hillary’s massive “hacking”

or coughing attack, yet it is #1 trending. What’s up? — Donald J. Trump (@realDonaldTrump) September 6, 2016

Former New York City Mayor Rudy Giuliani, a close adviser to Trump, also raised the issue of Clinton’s physical and mental health last month. “I think Hillary’s tired ... she looks sick,” he told Fox News Sunday, accusing the mainstream media of hiding evidence and urging people to Google “Hillary Clinton illness” to find support for his theory.

Before Dr Bardack’s statement, the former secretary of state’s doctor has repeatedly pronounced her health and fitness “excellent”. But there’s no denying Clinton’s “overheating” episode at such a high profile event couldn’t have come at a worse time for her campaign.

With just 58 days until election day, Sunday’s incident, combined with her coughing fit on Labor Day, is sure to undermine months of hard work from her campaign, which has been fighting to quell speculation about its candidate’s health.

“Those two things happening within six days of each other to a candidate who is 68 years old makes talk of Clinton’s health no longer just the stuff of conspiracy theorists,” Washington Post political reporter Chris Cillizza writes.

The campaign already released a summary of Clinton’s medical records and conditions last year, but Sunday’s collapse is sure to fuel the fire and could revive calls for both candidates to release updated detailed health records — something Trump has been pushing for.

The Republican candidate, who was also present during Sunday’s 9/11 memorial ceremony, didn’t immediately comment on Clinton’s pneumonia diagnosis. But he referenced the incident on Tuesday morning during an interview with Fox and Friends, saying health is “an issue” in the campaign.

“Something is going on but I hope she gets well,” Trump added.