US presidential candidate Hillary Clinton has insisted she is "doing great" after a health scare and has returned to the campaign trail ahead of the November election. 

However, following her recovery from pneumonia, the Democratic nominee faced a series of questions about her illness on her return to the campaign trail.

The 68-year-old former secretary of state said "sitting at home was pretty much the last place" she had wanted to be, but that the short break had allowed her to reflect on the campaign.

Speaking ahead of a rally in Greensboro, North Carolina, Mrs Clinton told media aboard her campaign plane: "Welcome back to 'Stronger Together'. I am doing great, thank you very much."

She later told supporters: "I tried to power through it but even I had to admit that maybe a few days of rest would do me good."

"I'm not great at taking it easy even under ordinary circumstances but with just two months to go until election day, sitting at home was pretty much the last place I wanted to be.

"When I’m under the weather, I can afford to take a few days off. Millions of Americans can’t." Hillary in NC today: https://t.co/rNM9eJ0fUi

— Hillary Clinton (@HillaryClinton) September 16, 2016

"But it turns out having a few days to myself was actually a gift."

In allowing her time to think about the campaign, Mrs Clinton said: "People like me, we're lucky."

"When I'm under the weather I can afford to take a few days off, millions of Americans can't, they either go to work sick or they lose a paycheck don't they?"

Concerns were raised over Mrs Clinton's health after she was was seen stumbling as she left a 9/11 memorial.
Her Republican rival Donald Trump has avoided directly referring to Mrs Clinton's medical problems but has made a veiled attack on her health.

He has since released a statement from his doctor, which says he is in very good condition.