US Secretary of State Hillary Clinton has been admitted to hospital with a blood clot related to a concussion she suffered earlier this month, after fainting and falling down.

Doctors at the New York Presbyterian hospital made the discovery after Clinton, 65, went for a follow-up exam, her deputy assistant said.

"She is being treated with anti-coagulants and is at New York-Presbyterian Hospital so that they can monitor the medication over the next 48 hours," Philippe Reines, the deputy assistant secretary of state told reporters on Sunday.

Reines would not comment on the location of the clot.

Clinton suffered a concussion earlier this month after reportedly passing out after becoming dehydrated from a stomach virus she had.

The incident saw her cancel testimony she was due to give to Congress about a report into the September 11 attack on the US diplomatic mission in Benghazi, Libya, that killed Ambassador Chris Stevens and three other Americans, the Associated Press reported.

She also missed a planned trip to the Middle East and north Africa following the fall.

Clinton had been due to return to work this week, before the discovery of the blood clot.

But she is due to stand down as secretary of state before US President Barack Obama officially begins his second term in January.


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  • US Sen. Hillary Rodham Clinton (D-NY) speaks as Amtrak Police Chief of Patrol and Special Operations John O'Connor looks on at a media conference about rail security in Penn Station April 2, 2004 in New York City. Security officials have received recent threats regarding the nation's railways. Clinton co-sponsored a bill with Sen. John McCain (R-AZ) calling for $570 million for security improvements to six rail tunnels serving New York. (Photo by Mario Tama/Getty Images)

  • U.S. Senator Hillary Rodham Clinton (D-NY) pauses prior to her speech during the "Health Action 2005," a grassroots conference on health care, January 27, 2005 at Renaissance Mayflower Hotel in Washington, DC. Clinton attacked the Bush Administration on cutting prescription drug benefits. (Photo by Alex Wong/Getty Images)

  • U.S. Senator Hillary Rodham Clinton (D-NY) reads documents during a hearing before the Senate Armed Services Committee June 23, 2005 on Capitol Hill in Washington, DC. The hearing was focused on U.S. military strategy and operations in Iraq. (Photo by Alex Wong/Getty Images)

  • Democratic presidential candidate Sen. Hillary Rodham Clinton stands in front of a large American flag as she speaks to supporters at Kirkwood Community College during a campaign stop in Cedar Rapids, Iowa, the day before the state's caucuses. (Photo by Michael Appleton/NY Daily News Archive via Getty Images)

  • Democratic presidential candidate US Senator Hillary Clinton addresses a campaign rally on April 14, 2008 in Bristol, Pennsylvania. (Photo by Charles Ommanney/Getty Images)

  • President Barack Obama and Secretary of State Hillary Rodham Clinton speak together sitting at a picnic table April 9, 2009, on the South Lawn of the White House. Official White House Photo by Pete Souza. (Credit: Getty)

  • Democratic presidential hopeful New York Senator Hillary Clinton speaks at her rally on the night of the Puerto Rico Democratic presidential primary, at the Condado Plaza Hotel and Casino in San Juan, Puerto Rico on June 1, 2008. AFP PHOTO / ROBYN BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

  • In this handout image supplied by the Israeli Government Press Office (GPO), Israeli President Shimon Peres meets with Secretary of State Hillary Clinton, on May 5, 2009 in Washington DC. Peres is on a four day visit that will include meetings with U.S. President Barack Obama, Vice-President Biden and U.N. Secretary General Ban Ki-moon. (Photo by Amos Ben Gershom/GPO via Getty Images)

  • U.S. Secretary of State Hillary Clinton meed with UK Foreign Secretary David Miliband January 21, 2010 at the State Department in Washington, DC. (Photo by Joshua Roberts/Getty Images)

  • In this handout image provided by Barbara Kinney, (L-R) U.S. Secretary of State Hillary Clinton, her mother Dorothy Rodham and Chelsea Clinton pose during the wedding of Chelsea Clinton and Marc Mezvinsky at the Astor Courts Estate on July 31, 2010 in Rhinebeck, New York. Chelsea Clinton, the daughter of former U.S. President Bill Clinton and Secretary of State Hillary Clinton, married Marc Mezvinsky today in an interfaith ceremony at the estate built by John Jacob Astor on the Hudson River about two hours north of New York City. (Photo by Barbara Kinney via WireImage)

  • Secretary of State Hillary Rodham Clinton (L) and former British first lady Cherie Blair (R) participate in an event at the State Department on October 7, 2010 in Washington, DC. The event was held to announce the GSMA mWomen Programme which is desinged to bring the benefits of mobile to women in developing markets worldwide. (Photo by Mark Wilson/Getty Images)

  • Hillary Clinton and President Obama at Feira Internacional de Lisboa (FIL) on November 19, 2010 in Lisbon, Portugal. The two day summit will address issues including a new strategic concept for NATO. Britain and the US will also seek an agreement to hand over responsibility for security in Afghanistan to local forces over the next four years.

  • President Barack Obama and Vice President Joe Biden, along with with members of the national security team, receive an update on the mission against Osama bin Laden in the Situation Room of the White House, May 1, 2011. Please note: a classified document seen in this photograph has been obscured. (Official White House Photo by Pete Souza)President Barack Obama and Vice President Joe Biden, along with with members of the national security team, receive an update on the mission against Osama bin Laden in the Situation Room of the White House, May 1, 2011. Please note: a classified document seen in this photograph has been obscured. (Official White House Photo by Pete Souza)

  • Secretary of State Hillary Clinton greets Congresswoman Gabriel Giffords. President Barack Obama delivers the State of the Union speech to a Joint Session of Congress on Capitol Hill Tuesday, January 24, 2012. (Photo by Melina Mara/The Washington Post)

  • U.S. Secretary of State Hillary Clinton testifies during a hearing before the House Foreign Affairs Committee October 27, 2011 on Capitol Hill in Washington, DC. Clinton testified on "Afghanistan and Pakistan: Transition and the Way Forward." (Photo by Alex Wong/Getty Images)

  • U.S. Secretary of State Hillary Clinton attends the National Prayer Breakfast in Washington, DC, February 2, 2012. (Photographer: Chris Kleponis/ Bloomberg News.)

  • Secretary of State Hillary Clinton (L) and British Prime Minister David Cameron share a laugh during a lunch hosted at the State Department on March 14, 2012 in Washington, DC. Cameron is on an official visit to Washington, where President Obama will host him at a State Dinner tonight. (Photo by Brendan Hoffman/Getty Images)

  • Hillary Clinton attends the Inaugural Women In Public Service Summer Institute at Wellesley College on June 11, 2012 in Boston, Massachusetts.

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  • John Kerry (2013-Present)

    John Kerry leaves a Senate Foreign Relations Committee markup on Jan. 29, 2013 after a vote was held on his confirmation as Secretary of State. (SAUL LOEB/AFP/Getty Images)

  • Hillary Clinton (2009-13)

    U.S. Secretary of State Hillary Clinton speaks at a press conference on November 14, 2012. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Condoleezza Rice (2005-09)

    Secretary of State Condoleezza Rice talks about the State Department's 2007 Country Reports on Human Rights Practices during a March 11, 2008 briefing in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Colin Powell (2001-05)

    U.S. Secretary of State Colin Powell speaks on June 22, 2004, about a corrected version of an inaccurate terrorism report issued by the government. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Madeleine Albright (1997-2001)

    U.S. Secretary of State Madeleine Albright delivers a Russia policy briefing on September 16, 1999 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Warren Christopher (1993-97)

    U.S. Secretary of State Warren Christopher briefs reporters on the peace process in Bosnia during a Dec. 8, 1995 press conference. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Lawrence Eagleburger (1992-93)

    Then-acting Secretary of State Lawrence Eagleburger listens to a reporter's question during a Nov. 18, 1992 news conference at the State Department. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • James Baker (1989-92)

    James Baker III waves to his associates at the US State Department on August 13, 1992. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • George P. Shultz (1982-89)

    U.S. Secretary of State George Shultz listens to a question during his first day of testimony before Iran-Contra investigators on July 23, 1987 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Alexander Haig (1981-82)

    Alexander Haig, Secretary of State-designate, a Reagan nominee on Monday, Dec. 23, 1980 in Washington for the announcement of selections. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Edmund Muskie (1980-81)

    (Pictured left) Freed hostage Richard Queen, right, greets well wishers at the State Department on Monday, July 21, 1980 in Washington. At left is Secretary of State Edmund Muskie. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Cyrus Vance (1977-80)

    Cyrus Vance, U.S. Secretary of State, pictured in 1979. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Henry Kissinger (1973-77)

    Secretary of State Henry Kissinger announces during an April 29, 1975 press conference in Washington that the evacuation of Americans from Vietnam and Saigon is complete, thus ending US involvement. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • William P. Rogers (1969-73)

    Israeli Defense Minister Moshe Dayan, left, and Secretary of State William P. Rogers begin talks at the Department of State on Feb. 7, 1972 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Dean Rusk (1961-69)

    Secretary of State Dean Rusk is shown during a news conference in Washington, D.C., on March 1, 1962. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Christian Herter (1959-61)

    President Dwight Eisenhower, left, says goodbye to Secretary of State Christian Herter in Gettsburg, Pennsylvania, on May 2, 1959 as Herter is about to board a helicopter on the President's farm to return to Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • John Foster Dulles (1953-59)

    U.S. Secretary of State John Foster Dulles (left) gets together with South Korean President Syngman Rhee in Seoul on August 4, 1953. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Dean Acheson (1949-53)

    U.S. Secretary of State Dean Acheson speaks from the State Department on Nov. 29, 1950 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • George C. Marshall (1947-49)

    Gen. George C. Marshall poses in his Red Cross office on Sept. 13, 1950 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • James F. Byrnes (1945-47)

    James F. Byrnes, United States Secretary of State, links arms with Associated Press correspondent, John Hightower, at Central Hall, Westminster in London, Jan. 15, 1946. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Edward Reilly Stettinius (1944-45)

    France's Foreign Minister Georges Bidault makes a VE Day radio statement from the Opera House in San Francisco, CA, May 8, 1945. Seated at the far right U.S. Secretary of State Edward Stettinius. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>) <em><strong>Correction</strong>: An earlier version of this text misspelled Stettinius' surname.</em>

  • Cordell Hull (1933-44)

    U.S. President Franklin Roosevelt is greeted by Secretary of State Cordell Hull on Sept. 15, 1938 in Washington. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Henry Lewis Stimson (1929-33)

    Henry Lewis Stimson, American Secretary of State for War shown around July 1931. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Frank B. Kellogg (1925-29)

    Former United States Secretary of State Frank B. Kellogg on Aug. 17, 1936 at Waterloo Station in London. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)

  • Charles Evans Hughes (1921-25)

    (Center) Former Secretary of State and Chief justice Charles Evans Hughes, pictured on on March 27, 1931. (Source: <a href="http://www.state.gov/secretary/former/">U.S. Department Of State</a>)