US Secretary of State Hillary Clinton was admitted to a New York hospital on Sunday with a blood clot linked to a concussion she suffered earlier this month, the State Department said in an announcement that looked sure to fuel speculation over the health of one of America’s best-known political figures.
Clinton, 65, has been out of the public spotlight since mid-December, when officials said she suffered a concussion after fainting due to a stomach virus contracted during a trip to Europe.
"In the course of a follow-up exam today, Secretary Clinton's doctors discovered a blood clot had formed, stemming from the concussion she sustained several weeks ago," State Department spokesman Philippe Reines said in a statement.
"She is being treated with anti-coagulants and is at New York-Presbyterian Hospital so that they can monitor the medication over the next 48 hours," Reines said. "They will determine if any further action is required."
US officials said on December 15 that Clinton, who cancelled an overseas trip because of the stomach virus, suffered a concussion after fainting due to dehydration.
They have since described her condition as improving and played down suggestions that it was more serious. She had been expected to return to work this week.
Clinton's illness, already the subject of widespread political speculation, forced her to cancel planned testimony to Congress on December 20 in connection with a report on the deadly attack on the US diplomatic post in Benghazi, Libya.
The attack became the subject of heated political debate in the run-up to the US presidential election in November, and Republican lawmakers have repeatedly demanded that Clinton appear to answer questions directly.
Clinton’s two top deputies testified in her place on the September 11 attack in Benghazi, which killed the US ambassador and three other Americans and raised questions about security at far-flung diplomatic posts.
Some Republican commentators have implied that Clinton was seeking to avoid questioning on the subject, suggestions that have been strongly rebutted by State Department officials.
Clinton has stressed that she remains ready to testify and was expected to appear before lawmakers this month before she steps down, as planned, around the time of Obama's inauguration for his second term in late January.
After narrowly losing the Democratic presidential nomination to Obama in 2008, Clinton has been consistently rated as the most popular member of his Cabinet and is often mentioned as a potential presidential candidate in 2016.
Any serious medical concern could throw a fresh question mark over her future plans, although she has frequently alluded to her general good health.