She is being treated with anti-coagulants and is at NewYork-Presbyterian Hospital so that they can monitor the medication over the next 48 hours.
Her doctors will continue to assess her condition, including other issues associated with her concussion. They will determine if any further action is required.
Clinton suffered a concussion earlier this month after she hit her head when she fainted because of dehydration from a stomach virus, a Clinton aide said.
No ambulance was called and she was not hospitalized, according to a state department official.
The stomach virus had caused Clinton to cancel a planned trip to North Africa and the United Arab Emirates, and also her scheduled testimony before Congress at hearings on the attack on the U.S. consulate in Benghazi, Libya.
Clinton originally fell ill from a stomach virus following a whirlwind trip to Europe at the beginning of the month, which caused such severe dehydration that she fainted and fell at home.
According to a U.S. official, the secretary had two teams of doctors, including specialists, examine her. They also ran tests to rule out more serious ailments beyond the virus and the concussion. During the course of the week after her concussion, Clinton was on an IV drip and being monitored by a nurse, while also recovering from the pain caused by the fall.