US Secretary of State Hillary Clinton, who skipped an overseas trip this week because of a stomach virus, has sustained concussion after fainting.
She is now recovering at home and being monitored by doctors.
An aide, Philippe Reines, said Mrs Clinton will work from home next week, at the recommendation of doctors.
Congressional aides do not expect her to testify as scheduled at congressional hearings on Thursday into the September 11 attack against a US diplomatic outpost in Benghazi, Libya, that killed four Americans, including the US ambassador.
The State Department said Mrs Clinton was dehydrated because of the virus and that she fainted, causing the concussion.