Secretary of State Hillary Clinton is convalescing after doctors found a blood clot during a routine examination following a concussion earlier in December.

The 65-year-old diplomat sustained a concussion after fainting at home in Washington, D.C. The fainting spell was brought on by a stomach virus contracted in Europe. State Department officials said after the clot was found on Sunday, Clinton is being kept at New York-Presbyterian Hospital for 48 hours and is being treated with anti-coagulants.

“Her doctors will continue to assess her condition, including other issues associated with her concussion. They will determine if any further action is required,” the State Department said in a statement.

Officials didn't provide further information on Clinton's condition, including where the clot was located. One rare side effect of concussions can be blood clot formation in the brain, but Clinton's short hospital stay suggests her condition is not as serious as that.

“I think what most people are speculating is that she has a deep venous thrombosis, most likely in her leg,” Allen J. Taylor, chief of cardiology at Georgetown University Medical Center, told the Washington Post.

Clinton has already had at least one blood clot in the leg before. In 1998, she was treated for a clot that formed behind her right knee during her 1998 U.S. Senate campaign. It's possible that resting from sickness and the concussion may have been the primary factor in the secretary's current condition; immobility can raise a person's risk for developing blood clots, especially if they are predisposed to them.

“If there is post concussive syndrome, you have persistent headaches, dizziness, nausea, and you feel poorly, so people end up lying in bed, which is a set up for a clot developing in the leg,” Massachusetts General Hospital neurologist Lee Schwamm told Time magazine.

The fact that Clinton is being treated with blood thinners is further evidence that the blood clot is likely not in her head, since blood thinners would increase the risk of bleeding and swelling in the brain, according to Schwamm.

But a blood clot in the leg is still quite serious -- they can break up into little bits that travel through a person's circulatory system and block off blood vessels in the heart or lungs. Blood thinners are a treatment that prevents clots from growing while the body dissolves it naturally.

Though the clotting property of blood can save your life when you're wounded, clots that form where they're not supposed to can be life-threatening. Many things can put a person at risk for blood clots, including dehydration, certain medications and certain inherited medical conditions. Long plane rides also raise a person's risk for developing blood clots in the legs, and Clinton keeps a pretty hectic schedule; she has visited more countries than any other secretary of state thus far, according to the Washington Post.