Clinton's office said Saturday she had sustained a concussion when she fainted after becoming dehydrated from a stomach bug, and the State Department said she was under doctor's orders to work from home this week.
John Bolton -- a Fox News Channel contributor and a former U.S. ambassador to the United Nations -- said Monday Clinton was using the injury as an excuse to avoid testifying Thursday about the death of U.S. Ambassador Christopher Stevens and three other Americans at a diplomatic mission in Benghazi, Libya.
"You know, every foreign service officer in every foreign ministry in the world knows the phrase I am about to use -- when you don't want to go to a meeting or conference or an event, you have a 'diplomatic illness,'" Bolton said. "And this is a 'diplomatic illness' to beat the band."
State Department spokeswoman Victoria Nuland told reporters Tuesday Clinton is "on the mend" and Bolton's charge is "completely untrue."
Several other conservative media figures and publications also suggested Clinton was faking illness, Politico said.
The New York Post said the development is "one of the most transparent dodges in the history of diplomacy." The Daily Caller insisted on seeing a medical report, to prove "she's not just stonewalling."
Nuland said Bolton and others who questioned the account of Clinton's illness "don't know what they're talking about."
"It's really unfortunate that in times like this people make wild speculation based on no information," she said.