Former US president Bill Clinton has been admitted to hospital with an infection, a spokesman for the 75-year-old said.
Doctors said Mr Clinton was responding well at the medical centre in Irvine, California.
The infection was not connected to the coronavirus.
"On Tuesday evening, President Clinton was admitted to UCI Medical Center to receive treatment for a non-Covid-related infection," the former president's spokesman Angel Urena wrote on Twitter.
"He is on the mend, in good spirits, and is incredibly thankful to the doctors, nurses and staff providing him with excellent care."
Doctors at the University of California Irvine Medical Center confirmed Mr Clinton had been admitted.
Mr Urena tweeted a statement from Mr Clinton's doctors at the hospital, Dr Alpesh Amin and Dr Lisa Bardack.
"President Clinton was taken to UC Irvine Medical Center and diagnosed with an infection," the hospital said.
"He was admitted to the hospital for close monitoring and administered IV (intravenous) antibiotics and fluids.
"He remains at the hospital for continuous monitoring. After two days of treatment, his white blood cell count is trending down and he is responding to antibiotics well."
"We hope to have him go home soon," the hospital added.
Mr Clinton will remain in hospital overnight, his spokesman said on Twitter, adding that the former president's health indicators were "trending in the right direction".
President Joe Biden said that Mr Clinton "seems to be, God willing, doing well".
Mr Biden made the comments at an event to promote his economic agenda.
He plans to speak with Mr Clinton later today.
An AFP correspondent at the hospital said the scene was subdued, with no sign of the VIP patient, other than a sizable media pack that had gathered in a car park.
CNN reported that a urinary tract infection had spread to Mr Clinton's bloodstream.
CNN's medical correspondent, Sanjay Gupta, said Mr Clinton had reported feeling fatigued during a visit to California on Tuesday and went to the hospital for testing that ruled out Covid-19 and heart-related problems.
Mr Clinton served as America's 42nd president, from 1993 to 2001. Elected at age 46, he was the third-youngest president in US history.
In 1998, he was impeached by the House of Representatives - only the second president in US history to earn the ignominious distinction - for lying about his affair with White House intern Monica Lewinsky. He was ultimately acquitted by the Senate in February 1999.
In 2004, at age 58, he underwent a quadruple bypass operation after doctors found signs of extensive heart disease.
After his health scare, Mr Clinton - who had a reputation for loving fatty foods - adopted a vegan diet.
In 2010 he underwent stent surgery after complaining of heart pains.
That same year, he said his decision to go vegan was not a difficult one.
"Not when you have [had a] quadruple heart bypass and you want to live to be a grandfather," Mr Clinton said at an event organised in Dallas by People for the Ethical Treatment of Animals.