Former president Bill Clinton has been hospitalised with a non-COVID-related infection.
Clinton's doctors said it was a blood infection.
Clinton, 75, was admitted to a hospital in Irvine in Southern California on Tuesday evening, his spokesperson Angel Urena tweeted.
"He is on the mend, in good spirits and is incredibly thankful to the doctors, nurses, and staff providing him with excellent care," Urena said.
The University of California Irvine Medical Center confirmed Clinton was admitted there but said nothing else.
Urena later tweeted a statement from Clinton's doctors saying Clinton was admitted "for close monitoring and administered IV antibiotics and fluids."
It added: "After two days of treatment his white blood cell count is trending down and he is responding to antibiotics well."
The doctors said they are in non-stop touch with Clinton's New York-based medical team including his cardiologist and "we hope to have him go home soon."
CNN reported that a urinary tract infection spread to Clinton's bloodstream.
The news channel's medical correspondent, Sanjay Gupta, said 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.
Clinton served as America's 42nd president, from 1993 to 2001. Elected at the age of 46, he was the third-youngest president in US history and the first Baby Boomer to hold office.
In 1998, Clinton was impeached by the House of Representatives - only the second president in American 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, Clinton - who had a reputation for loving fatty foods - began a vegan diet.
In 2010 Clinton underwent stent surgery after complaining of heart pains.
That same year he said his decision to go vegan was not a difficult one to make.
"Not when you have [had a] quadruple heart bypass and you want to live to be a grandfather," Clinton said at an event organised in Dallas by People for the Ethical Treatment of Animals.