hep·​a·​rin ˈhe-pə-rən How to pronounce heparin (audio)
: a mucopolysaccharide sulfuric acid ester that is found especially in the liver and lungs, that prolongs the clotting time of blood, and that is used medically in the form of its sodium salt
heparinized adjective

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Heparin is an organic compound used to prevent blood from clotting in the heart or blood vessels during and after surgery, and for initial treatment of various heart, lung, or circulatory disorders in which there is an increased risk of blood clotting. A mixture of complex carbohydrate molecules, heparin occurs naturally in liver and lung tissues. It was discovered in 1922 and originally used to prevent clotting in blood taken for laboratory tests.

Examples of heparin in a Sentence

Recent Examples on the Web Pig products go into dozens of life-saving drugs like epinephrine, which is used to treat severe allergic reactions, and heparin, a blood thinner. Jen Christensen, CNN, 30 Jan. 2024 The condition is typically treated with aspirin and low molecular weight heparin (LMWH) during pregnancy. Sadia Rafiquddin, STAT, 31 Aug. 2023 It is thought that treatment of TTS with heparin could make the condition worse, and at the onset of the pause, the CDC alerted health care providers to avoid use of heparin. NBC News, 12 May 2021 The concern is that giving heparin to such patients would worsen their condition. Erika Edwards, NBC News, 16 Apr. 2021 In the future, these animals might be the source of the blood thinner heparin or even organs for transplant in those sensitized to the alpha-gal sugar. Peter G. Lurie and Beth Ellikidis, STAT, 17 Apr. 2023 Hospitalized patients will receive either low or high doses of heparin while those being treated outside of a hospital will get either apixaban, aspirin, or a placebo. Anna Edney, Bloomberg.com, 10 Sep. 2020 Other instances of contaminated products from overseas included blood pressure medications suspected of containing a possible carcinogen and deadly batches of heparin, both of which prompted mass recalls. Andrew Jacobs, New York Times, 3 Apr. 2023 They may also be restricted in using certain medication such as heparin, which uses pig intestines. Jocelyn Solis-Moreira, Popular Science, 27 Mar. 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'heparin.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


International Scientific Vocabulary, from Greek hēpar liver

First Known Use

1918, in the meaning defined above

Time Traveler
The first known use of heparin was in 1918

Dictionary Entries Near heparin

Cite this Entry

“Heparin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/heparin. Accessed 20 Jul. 2024.

Medical Definition


hep·​a·​rin ˈhep-ə-rən How to pronounce heparin (audio)
: a glycosaminoglycan sulfuric acid ester that occurs especially in the liver and lungs, that prolongs the clotting time of blood by preventing the formation of fibrin, and that is administered parenterally in the form of its sodium salt in vascular surgery and in the treatment of postoperative thrombosis and embolism see liquaemin compare antiprothrombin, antithrombin

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