- Drugs that doctors are using offer clues to clot's location, Dr. Sanjay Gupta says
- The clot was discovered in a follow-up exam related to her concussion
- Clinton is expected to remain hospitalized for at least the next 48 hours
- She was scheduled to return to work this week after recovering from the concussion
(CNN) -- Secretary of State Hillary Clinton was hospitalized Sunday after doctors discovered a blood clot during a follow-up exam related to
a concussion she suffered this month, her spokesman said.
She is expected to remain at New York Presbyterian Hospital for the next 48 hours so doctors can monitor her condition and treat her with anticoagulants, said Philippe Reines, deputy assistant secretary of state.
"Her doctors will continue to assess her condition, including other issues associated with her concussion," Reines said. "They will determine if any further action is required."
Reines did not specify where the clot was discovered.
Clinton, 65, was suffering from a stomach virus earlier this month when she fainted because of dehydration, causing the concussion.
Secretary of State Hillary Clinton speaks about North Africa at the Center for Strategic & International Studies on October 12, 2012, in Washington. From her early days as a lawyer to one of the most powerful people in Washington, here's a look at Clinton at through the years:
Hillary Rodham, center, a lawyer for the Rodino Committee, and John Doar, left, chief counsel for the committee, bring impeachment charges against President Richard Nixon in the Judiciary Committee hearing room at the U.S. Capitol in 1974.
Arkansas Gov. Bill Clinton helps first lady Rosalynn Carter on a campaign swing through Arkansas in June 1979. Also seen is Hillary Clinton (center background).
Bill Clinton embraces his wife shortly after a stage light fell and knocked her down on January 26, 1992. They talk to Don Hewitt, producer of the CBS newsmagazine "60 Minutes."
With Hillary, Democratic presidential candidate Bill Clinton waves to the crowd during his victory party after winning the Illinois primary on March 17, 1992.
Al Gore, from left, his wife, Tipper, Bill Clinton and Hillary Clinton wave to supporters at the Chautauqua Institution in Chautauqua, New York, on August 23, 1992, after they gave speeches on family values.
Clinton gestures at a campaign rally November 3, 1992, in Denver. After taking office, President Bill Clinton chose his wife to head a special commission on health care reform, the most significant public policy initiative of his first year in office.
Bill and Hillary Clinton have a laugh together on Capitol Hill in 1993.
Clinton pours herself a cup of tea during her testimony to the Senate Education and Labor Committee on health care reform in 1993.
Clinton speaks at George Washington University on September 10, 1993, in Washington, during her husband's first term.
Clinton, left, waves to the media on January 26, 1996, as she arrives at federal court in Washington for an appearance before a grand jury. The first lady was subpoenaed to testify as a witness in the investigation of the Whitewater land deal in Arkansas.
Hillary Clinton looks on as President Bill Clinton addresses the Monica Lewinsky scandal in the Roosevelt Room at the White House on January 26, 1998.
Hillary and Bill Clinton arrive at Foundry United Methodist Church on August 16, 1998, in Washington. He became the first sitting president to testify before a grand jury when he testified via satellite about the Monica Lewinsky matter.
Clinton shakes hands during a St. Patrick's Day parade in the Sunnyside neighborhood of Queens, New York, on March 5, 2000.
Clinton waves to the crowd as she arrives on the stage at the Democratic National Convention on August 14, 2000, at the Staples Center in Los Angeles.
Clinton campaigns for a Senate seat at Grand Central Station on October 25, 2000, in New York.
First lady Hillary Clinton is sworn in as a senator in a re-enactment ceremony with U,S. President Bill Clinton, from left, nephew Tyler, daughter Chelsea, brother Hugh Rodham, mother Dorothy Rodham and Vice President Al Gore in the Old Senate Chamber on Capitol Hill on January 3, 2001, in Washington.
Andrew Cuomo, from left, Eliot Spitzer and Clinton celebrate with the crowd of Democratic supporters after their wins in their various races on November 7, 2006, in New York City.
Clinton speaks during a post-primary rally on January 8, 2007, at Southern New Hampshire University in Manchester, New Hampshire.
Hillary and Bill Clinton pay a visit to the 92nd Annual Hopkinton State Fair on September 2, 2007, in Contoocook, New Hampshire.
Clinton speaks at a fall kick-off campaign rally on September 2, 2007, in Portsmouth, New Hampshire.
Clinton addresses a question during a Democratic Presidential Candidates Debate at Dartmouth College in Hanover, New Hampshire, on September 26, 2007.
Felipe Bravo, left, and Christian Caraballo are covered with Hillary Clinton stickers in downtown Manchester, New Hampshire, on January 8, 2008.
Clinton campaigns with her daughter, Chelsea, on January 1, 2008, in Council Bluffs, Iowa, two days ahead of the January 3 state caucus.
Sen. Clinton waves as she speaks to supporters at the National Building Museum on June 7, 2008, in Washington. Clinton thanked her supporters and urged them to back Sen. Barack Obama to be the next president of the United States.
Barack Obama and Clinton talk on the plane on their way to a Unity Rally in Unity, New Hampshire, on June 27, 2008.
U.S. Democratic presidential candidate Barack Obama watches Sen. Hillary Clinton address the Democrate National Convention at a Democratic supporters' group in Billings, Montana, on August 26, 2008. The two endured a long, heated contest for the 2008 nomination.
Sen. Charles Schumer, left, looks toward Secretary of State designate Clinton as committee chairman Sen. John Kerry, center, looks on during nomination hearings on January 13, 2009, on Capitol Hill.
Clinton testifies during her confirmation hearing for secretary of state before the Senate Foreign Relations Committee on Capitol Hill on January 13, 2009, in Washington.
Clinton dances with a local choir as while visiting the Victoria Mxenge Housing Project in Philippi on the outskirts of Cape Town, Souith Africa, on August 8, 2009.
Clinton looks through binoculars toward North Korea during a visit to observation post Ouellette at the Demilitarized Zone seperating the two Koreas in Panmunjon on July 21, 2010.
Clinton walks up the steps to her aircraft at sunset as she leaves an ASEAN meeting July 23, 2010, in Hanoi, Vietnam.
From left: Marc Mezvinsky, Hillary Clinton, Chelsea Clinton and Bill Clinton pose during the wedding of the young couple at the Astor Courts Estate on July 31, 2010, in Rhinebeck, New York.
U.S. President Barack Obama and Clinton hold a moment of silence before a NATO meeting on November 19, 2010, in Lisbon, Portugal.
Clinton listens as Turkish Foreign Minister Ahmet Davutoglu (not in picture) makes a brief statement before a bilateral meeting at the State Department in Washington on November 29, 2010.
Clinton shakes hands with a child during an unannounced walk through Tahrir Square in Cairo, Egypt, on March 16, 2011.
President Barack Obama, Vice President Joe Biden, Clinton and members of the national security team receive an update on the mission against Osama bin Laden in the Situation Room of the White House on May 1, 2011.
Clinton checks her PDA upon departure in a military C-17 plane from Malta bound for Tripoli, Libya, on October 18, 2011.
Clinton speaks as Hamid Karzai, president of Afghanistan, listens during a news conference at the presidential palace in Kabul on July 7.
Clinton arrives at Ben Gurion International Airport on July 15, in Lod, outside Tel Aviv, Israel.
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How dangerous are blood clots?
Blood clots "are clumps that occur when blood hardens from a liquid to a solid," according to the National Institutes for Health.
Clots can form inside veins or arteries or even the heart, the NIH says. "A blockage in the vein will usually cause fluid buildup and swelling," the NIH website says. Among the possible threats: Sometimes, a "clot can break loose and travel from one location in the body to another."
Sometimes, it can "partly or completely block" blood flow in a blood vessel. If a clot blocks an artery, it may "prevent oxygen from reaching the tissues in that area," the NIH says.
If not "treated promptly, it can lead to tissue damage or death."
Dr. Sanjay Gupta, CNN chief medical correspondent, says the fact that Clinton's clot is being treated with anticoagulants may offer a clue to the clot's location.
Anticoagulants are drugs that prevent clots from forming in the heart veins and arteries, according to the American Heart Association. Anticoagulants also prevent clots from growing larger.
"I think it's very unlikely this is a blood clot on top of the brain or around the brain specifically, because you just don't treat blood clots on the brain that way," Gupta said. "That would worsen the bleeding."
Clinton spent the holidays with her family last week after working from home.
She was scheduled to return to work at the State Department this week after being sidelined for the past three weeks. Her illness forced her to bow out of testifying on December 20 before the House Foreign Affairs Committee on the deadly attack on the U.S. Consulate in Benghazi, Libya. Deputies Thomas Nides and Bill Burns appeared in her place.
Report blames poor security, inadequate response in Benghazi attack
The medical setback comes as Clinton is wrapping up her busy tenure as secretary of state, during which she has logged more than 400 travel days and nearly a million miles. She plans to step down from the post if and when Sen. John Kerry -- President Barack Obama's choice to replace her -- is confirmed by the Senate.
Read more: Hillary Clinton fast facts
CNN White House Correspondent Jessica Yellin contributed to this report.
