— -- Democratic presidential candidate Hillary Clinton left the 9/11 memorial ceremony Sunday because she felt "overheated," her campaign said, and her personal doctor later revealed that she had been diagnosed with pneumonia on Friday.
Here are some of the other times the presidential candidate's health has been in the headlines in recent years:
December 2012: Clinton suffers a concussion after fainting in her home
As a result of the concussion, Clinton wore glasses for a period of time to help her with a double vision issue. Former President Bill Clinton would later say it took Clinton six months to fully recover form the concussion.
January 2013: Clinton suffers from a blood clot
In a follow-up doctor appointment to monitor the progress of her concussion recovery, doctors discovered the secretary of state had a blood clot. Clinton was treated with blood thinners, according to her doctors, and remained at the hospital for several days.
June 2014: Clinton tells Diane Sawyer there are no "lingering effects" from her concussion
In an interview with ABC News' Diane Sawyer, more than a year after her tenure as secretary of state ended, Clinton said that there were no lingering effects from her concussion and clot, but she did admit the medical incident was serious. "It was, I think, a serious concussion, she said "... Because of the force of the fall, I had double vision for a short period of time and I had some dizziness. ... No lingering effects."
July 2015: Clinton's physician releases a two-page statement, saying the candidate is "healthy"
Hillary Clinton's doctor Dr. Lisa Bardack released a statement in the summer of 2015, saying the presidential candidate was "healthy." Bardack said Clinton was "a healthy 67 year old female whose current medical conditions include hypothyroidism and seasonal pollen allergies."
"She is in excellent physical condition and fit to serve as President of the United States," Bardack said.
Campaign 2016: Clinton suffers from periodic coughing fits
Presidential candidate Clinton suffered from a number of coughing fits in interviews and events as she hit the campaign trail in her bid for the presidency.
Most recently the candidate suffered an almost two-minute-long coughing fit during a Labor Day rally in Cleveland, Ohio. The candidate made a joke out of the situation, saying it was an allergic reaction to her opponent Donald Trump. "Every time I think of Trump, I get allergic," she said. Clinton had a similar coughing fit on her plane that day and several times in past months, often prompting her to sip water and take a throat lozenge.
Campaign 2016: Trump attacks Clinton for a lack of "stamina"
Frequently over the course of the campaign, particularly after the conventions in July, Trump attacked Clinton for lacking "stamina." In August 2016, he called her "unstable Hillary Clinton" at multiple campaign rallies. "I don't think she's all there," he said at a rally in Windham, New Hampshire.
August 2016: Clinton discusses health with Jimmy Kimmel, expresses frustration at the rumors
In an appearance on "Jimmy Kimmel Live" on August 22, Clinton got lighthearted about her health, joking around with Kimmel about the rumors. "Back in October the National Enquirer said I would be dead in six months," she said. When she challenged Kimmel to take her pulse, he joked there wasn't one.
The candidate did express exasperation at the specific charge of health issues. "I don't know why they are saying this," she said. "I think on the one hand it's part of the wacky strategy. Just say all these crazy things and maybe you'll get some people to believe you." Clinton added that she doesn't question Trump's health. "I mean as far as I can tell he's as healthy as a horse," she said.
Kimmel then challenged her to open a jar of pickles, which she did.
September 2016: Clinton defends the pace of her campaign to David Muir
In an interview with ABC News' David Muir, Clinton defended the pace of her campaign. When asked if she was being out-campaigned, she told him: "No. Not at all."
September 2016: Trump tells David Muir he thinks both he and Clinton should release medical records
As of September 11, neither campaign has released their candidate's full medical records. But on September 5, Trump told Muir that he thought both he and Clinton should release them. When asked why he doesn't release his full records first, he told Muir he will release his medical records. "I might do that. I might do that," Trump said. "In fact, now that you ask, I think I will do that."
ABC's Nicole Phillip and Sunny Choo contributed to this report