Libertarian presidential nominee Gary Johnson Gary Earl JohnsonWhat the numbers say about Trump's chances at reelection Presidential race tightens in Minnesota as Trump plows resources into state The Hill's Campaign Report: Biden condemns violence, blames Trump for fomenting it l Bitter Mass. primaries reach the end l Super PAC spending set to explode MORE says Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE should "take a few more days off" to recover from pneumonia.

“When it comes to Hillary, what I think that this demonstrates is just how hard it is to run for president," Johnson said on Fox Business. "I mean talking about burning the candle at both ends."

ADVERTISEMENT

"I am concerned for her. I think she probably should take a few more days off. I mean, pneumonia is something very serious," he added.

"Are you saying that as a competitor?" host Maria Bartiromo asked.

"I'm certainly not suggesting for the next 50 days [until the election], but it seems to me that maybe a few more days off. Pneumonia is really serious," Johnson said.

"This kills a lot of people," he continued. "So, something to be taken really seriously, and I hope she's OK, and I'm sure she is."

Clinton's campaign canceled a fundraising trip to California on Monday and Tuesday after disclosing over the weekend that she'd been diagnosed with pneumonia.

The campaign only disclosed the condition after a video showed Democratic nominee leaving a 9/11 memorial early on Sunday. In the video, Clinton appeared to collapse and was helped into a van.

Clinton told CNN's Anderson Cooper on Monday night that she'd return to the campaign trail sometime this week.

"Obviously I was supposed to rest five days," she said. "That’s what they told me on Friday, and I didn’t follow that very wise advice."

Clinton's husband, former President Bill Clinton William (Bill) Jefferson ClintonGOP brushes back charges of hypocrisy in Supreme Court fight Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE, will campaign on behalf of his wife Wednesday at a rally in Las Vegas.

For his part, Johnson says he considers himself to be in top health.

"I’m in the 1 percent of 1 percent when it comes to health," Johnson, who is an avid skier and bicyclist, told Fox Business. "I do believe I’m like one in a thousand, but I’ve dedicated my life to health and fitness."