he·​mo·​glo·​bin | \ˈhē-mə-ˌglō-bən \

Definition of hemoglobin 

1 : an iron-containing respiratory pigment of vertebrate red blood cells that consists of a globin composed of four subunits each of which is linked to a heme molecule, that functions in oxygen transport to the tissues after conversion to oxygenated form in the gills or lungs, and that assists in carbon dioxide transport back to the gills or lungs after surrender of its oxygen

2 : any of numerous iron-containing respiratory pigments of various organisms (such as invertebrates and yeasts)

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Did You Know?

When filled with oxygen, the hemoglobin in your blood is bright red; returning to the lungs without its oxygen, it loses its brightness and becomes somewhat bluish. Hemoglobin levels can change from day to day, and may be affected by such factors as a lack of iron in the diet, a recent loss of blood, and being pregnant. When you give blood, a nurse first pricks your finger to test your hemoglobin level; a low hemoglobin count indicates anemia and may mean that you shouldn't give blood that day. Mild anemia is generally of little importance, but some types can be very serious.

Examples of hemoglobin in a Sentence

Recent Examples on the Web

Leghemoglobin is an iron-containing protein pulled from soybean roots that’s similar to hemoglobin, an oxygen-carrying protein in red blood cells. Beth Mole, Ars Technica, "PETA roasts Impossible Burger for rat tests, suggests patties cause cancer," 11 Aug. 2018 Methemoglobinemia is a rare blood disorder that reduces the amount of hemoglobin, the protein that carries oxygen, in the blood. Korin Miller, SELF, "The FDA Wants Benzocaine Teething Products Taken Off the Market," 24 May 2018 The most recent success has been hemoglobin (by [Max Ferdinand] Perutz); the model of this protein contains 10,000 atoms. Daniel C. Schlenoff, Scientific American, "“Foul Treachery” of Trotsky and Lenin in 1918; Phineas Gage’s Brain in 1868," 13 July 2018 The tabletop device is also capable of doing instant blood analyses like white blood cell counts and hemoglobin measurements, which could mean blood samples don’t need to be sent away to a lab. Emily Matchar, Smithsonian, "A Robot May One Day Draw Your Blood," 13 July 2018 Their bodies will produce more hemoglobin — the molecule in blood to which oxygen binds — and more oxygen will be carried to their brains and bodies. Brian Resnick, Vox, "Why the trapped Thai soccer team is in increasing trouble: they’re running out of oxygen," 6 July 2018 At the median, the four patients are producing 39 percent anti-sickling hemoglobin. Adam Feuerstein, STAT, "New Bluebird data show promising benefits for gene therapy, if they last," 15 June 2018 The patient’s total hemoglobin level is equivalent to what’s recorded in a fully healthy person. Adam Feuerstein, STAT, "New Bluebird data show promising benefits for gene therapy, if they last," 15 June 2018 By this point in pregnancy, the second trimester, an affected fetus has little or no working hemoglobin, the molecule that carries oxygen to cells all over the body. New York Times, "Five Blood Transfusions, One Bone Marrow Transplant — All Before Birth," 25 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'hemoglobin.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of hemoglobin

1869, in the meaning defined at sense 1

History and Etymology for hemoglobin

International Scientific Vocabulary, short for earlier hematoglobulin

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Last Updated

13 Nov 2018

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The first known use of hemoglobin was in 1869

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English Language Learners Definition of hemoglobin

: the part of blood that contains iron, carries oxygen through the body, and gives blood its red color


he·​mo·​glo·​bin | \ˈhē-mə-ˌglō-bən \

Kids Definition of hemoglobin

: a protein of red blood cells that contains iron and carries oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs


variants: or chiefly British haemoglobin \ ˈhē-​mə-​ˌglō-​bən \

Medical Definition of hemoglobin 

1 : an iron-containing respiratory pigment of vertebrate red blood cells that functions primarily in the transport of oxygen from the lungs to the tissues of the body, that consists of four polypeptide chains of which two are of the type designated alpha and two are of one of the types designated beta, gamma, or delta and each of which is linked to a heme molecule, that combines loosely and reversibly with oxygen in the lungs or gills to form oxyhemoglobin and with carbon dioxide in the tissues to form carbaminohemoglobin, that in humans is present normally in blood to the extent of 14 to 16 grams in 100 milliliters expressed sometimes on a scale of 0 to 100 with an average normal value (as 15 grams) taken as 100, and that is determined in blood either colorimetrically or by quantitative estimation of the iron present — see fetal hemoglobin, hemoglobin a — compare carboxyhemoglobin, methemoglobin

2 : any of numerous iron-containing respiratory pigments of various organisms (as invertebrates and yeasts)

Other Words from hemoglobin

hemoglobinic or chiefly British haemoglobinic \ ˌhē-​mə-​glō-​ˈbin-​ik \ adjective
hemoglobinous or chiefly British haemoglobinous \ -​ˈglō-​bə-​nəs \ adjective

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More from Merriam-Webster on hemoglobin

Spanish Central: Translation of hemoglobin

Nglish: Translation of hemoglobin for Spanish Speakers

Britannica English: Translation of hemoglobin for Arabic Speakers

Britannica.com: Encyclopedia article about hemoglobin

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