vitamin K
noun
1
: either of two naturally occurring fat-soluble vitamins essential for the clotting of blood because of their role in the production of clotting factors in the liver:
a
or vitamin K1
: the vitamin C31H46O2 that is produced by plants and obtained especially from green leafy vegetables (such as collards and kale)
b
or vitamin K2
: the vitamin C41H56O2 that is produced by bacteria (as in the intestines of animals) and obtained especially from meat and fermented foods
2
a
or vitamin K3
: menadione
b
: any of several synthetic compounds chemically related to menadione
Examples of vitamin K in a Sentence
Recent Examples on the Web
Babies need vitamin K to help their blood clot, but they aren’t born with enough of it in their system.
—
Duaa Eldeib, ProPublica, 18 May 2026
Additionally, 1 in every 5 babies with vitamin K deficiency bleeding will die.
—Vanessa Etienne, PEOPLE, 8 May 2026
The number of deaths directly attributed to vitamin K deficiency bleeding appears to be small — fewer than a dozen annually — but has started to climb in recent years, according to death certificate data from federal and state agencies.
—Duaa Eldeib, CNN Money, 8 May 2026
Normal sources of nutrition for newborns, including breast milk, do not contain enough vitamin K to make up for this deficiency in the early months of life.
—Mary Walrath-Holdridge, USA Today, 8 May 2026
See All Example Sentences for vitamin K
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Duaa Eldeib, ProPublica, 18 May 2026
Additionally, 1 in every 5 babies with vitamin K deficiency bleeding will die.
—Vanessa Etienne, PEOPLE, 8 May 2026
The number of deaths directly attributed to vitamin K deficiency bleeding appears to be small — fewer than a dozen annually — but has started to climb in recent years, according to death certificate data from federal and state agencies.
—Duaa Eldeib, CNN Money, 8 May 2026
Normal sources of nutrition for newborns, including breast milk, do not contain enough vitamin K to make up for this deficiency in the early months of life.
—Mary Walrath-Holdridge, USA Today, 8 May 2026
See All Example Sentences for vitamin K
Cite this Entry
“Vitamin K.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/vitamin%20K. Accessed 23 May. 2026.
Copy CitationMedical Definition
vitamin K
noun1
: either of two naturally occurring fat-soluble naphthoquinone vitamins essential for the clotting of blood because of their role in the production of clotting factors in the liver:
a
or vitamin K1
: a yellow oily vitamin C31H46O2 that is produced by plants and obtained especially from green leafy vegetables (such as collards and kale) and is often used to treat hypoprothrombinemia
called also phylloquinone, phytonadione
b
or vitamin K2
: a pale yellow crystalline vitamin C41H56O2 that is produced by bacteria (as in the intestines of animals) and obtained especially from meat and fermented foods and that typically has greater bioavailability than vitamin K1
called also menaquinone
2
a
or vitamin K3
: menadione
b
: any of several synthetic compounds chemically related to menadione
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