Clinton recovering from blood clot
Mrs Clinton has said she intends to appear before Congress to discuss the attack - in which four Americans, including the US ambassador to Libya, died - but it is unclear when she will be back at work.
The doctors gave no estimate of when she may go home from the hospital.
On Sunday, a State Department spokesman said Mrs Clinton was "being treated with anti-coagulants and is at New York-Presbyterian Hospital so that they can monitor the medication over the next 48 hours".
Mrs Clinton's condition is unusual, but by no means unheard of.
"This condition is not very common, but it certainly happens," said Dr Raj Narayan, chair of neurosurgery at North Shore University Hospital and Long Island Jewish Medical Center in New York. It probably happens more often than we realise, he said,
because it must be diagnosed with an MRI, as Mrs Clinton's was.
Narayan, who is not treating Clinton, said it likely was caused by her dehydration and the concussion that occurred from her fall. Head trauma can cause blood clots, Dr Narayan said, because the injury triggers the production of thromboplastin, a blood protein that causes the blood to clot.
The severity depends in part on how someone is built, he said.
People normally have two of the veins where Mrs Clinton suffered the clot. Some people, however, have only one, while others have two but one is much larger than the other. The prognosis is typically better if you have two normal veins because the blood could flow through the other vein if one is blocked.
"Think of it as two pipes draining all of the blood out of the brain," Dr Narayan said. "If one is blocked and the other is open, there is no problem. But if both pipes are blocked, you are in trouble."
Dr Geoffrey Manley, chief of neurosurgery at San Francisco General Hospital and professor of neurosurgery at the University of California San Francisco (UCSF), said the condition can be fatal if not treated but that most patients recover well.
"Left untreated, these things could be fatal. But typically, injuries to the transverse sinus, if treated appropriately, patients typically do very well," Dr Manley said.
Dr Manley, who is also not involved in Mrs Clinton's treatment, said it was quite possible she would be out of the hospital in a week or less and the condition was not likely to have long-term effects or to be the harbinger of more clots over time.
"One doesn't necessarily dictate another one," he said.
"This is ultimately not going to cause any long-term brain problems for her, and I think that it's a message to the public that when you fall and hit your head, you need to be evaluated by somebody that takes care of brain-injured patients," he added.