The Chappaqua resident was scheduled to testify before Congressional panels looking into the Sept. 11 attacks against a diplomatic outpost in Benghazi, Libya.
She sustained the concussion on Thursday after having fainted at home earlier in the week, a state department official said.
As advised by her doctors, Clinton, 65, has been recovering at her Chappaqua home she shares with husband President Bill Clinton, staying in contact with other top government officials.
State department officials William Burns and Thomas Nides will stand in for the secretary at the hearings in Congress.
Clinton plans to leave her position as Secretary of State soon. Senator John Kerry is reportedly being considered for the job.
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