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

-ˈkā-ˈwən 

: the vitamin C₃₁H₄₆O₂ that is produced by plants and obtained especially from green leafy vegetables (such as collards and kale)

b

or vitamin K₂

-ˈkā-ˈtü 

: 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

-ˈkā-ˈthrē 

: menadione

b

: any of several synthetic compounds chemically related to menadione

Examples of vitamin K in a Sentence

Recent Examples on the Web

Newborns are routinely given a standard vitamin K injection right after birth to prevent deficiency. —Beth Thomas, Verywell Health, 27 May 2026

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

Without a vitamin K shot, babies can develop vitamin K deficiency bleeding (VKDB), a condition where infants are at risk of bleeding into their intestines and brain. —Vanessa Etienne, PEOPLE, 8 May 2026

The number of deaths recorded as being the direct result of vitamin K deficiency bleeding remains small, said the outlet, but has climbed in recent years. —Mary Walrath-Holdridge, USA Today, 8 May 2026

Word History

Etymology

from the initial letter of Danish & Swedish koagulation coagulation, Norwegian koagulasjon & German Koagulation

First Known Use

1935, in the meaning defined at sense 1

Rhymes for vitamin K

• aaa
• alleyway
• alumnae
• anime
• anyway
• arete
• attache
• axillae
• baa
• beaujolais
• bouvier
• breakaway

Kids Definition

vitamin K

noun

: any of several vitamins that are needed in order for blood to clot properly

Medical Definition

vitamin K

noun

1

: 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

-ˈkā-ˈwən 

: 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

-ˈkā-ˈtü 

: 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

-ˈkā-ˈthrē 

: menadione

b

: any of several synthetic compounds chemically related to menadione