US Secretary of State Hillary Clinton has been admitted to hospital with a blood clot related to a concussion she suffered earlier this month, after fainting and falling down.
Doctors at the New York Presbyterian hospital made the discovery after Clinton, 65, went for a follow-up exam, her deputy assistant said.
"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," Philippe Reines, the deputy assistant secretary of state told reporters on Sunday.
Reines would not comment on the location of the clot.
Clinton suffered a concussion earlier this month after reportedly passing out after becoming dehydrated from a stomach virus she had.
The incident saw her cancel testimony she was due to give to Congress about a report into the September 11 attack on the US diplomatic mission in Benghazi, Libya, that killed Ambassador Chris Stevens and three other Americans, the Associated Press reported.
She also missed a planned trip to the Middle East and north Africa following the fall.
Clinton had been due to return to work this week, before the discovery of the blood clot.
But she is due to stand down as secretary of state before US President Barack Obama officially begins his second term in January.