WASHINGTON — US Secretary of State Hillary Rodham Clinton remained under observation Monday at a New York City hospital after being treated for a blood clot related to the concussion she sustained earlier this month. Clinton's doctors discovered the clot Sunday while performing a follow-up exam, her spokesman, Philippe Reines, said. He would not elaborate on the location of the clot but said Clinton was being treated with anti-coagulants and would remain at New York-Presbyterian Hospital for at least the next 48 hours so doctors can monitor the medication. “Her doctors will continue to assess her condition, including other issues associated with her concussion,” Reines said in a statement. “They will determine if any further action is required.” Clinton, 65, fell and suffered a concussion while at home alone in mid-December as she recovered from a stomach virus that left her severely dehydrated. The concussion was diagnosed Dec. 13, and Clinton was forced to cancel a trip to North Africa and the Middle East that had been planned for the next week. The former first lady and senator, who had planned to step down as America's top diplomat in January, is known for her grueling travel schedule. She is the most traveled secretary of state in history, having visited 112 countries while in the job. The seriousness of a blood clot “depends on where it is,” said Dr. Gholam Motamedi, a neurologist at Georgetown University Medical Center who was not involved in Clinton's care. Clots in the legs are a common risk after someone has been bedridden, as Clinton may have been for a time after her concussion. Those are “no big deal” and are treated with six months of blood thinners to allow them to dissolve on their own and to prevent further clots from forming, he said. — AP