Vitamin K

Pronunciation: VY-tuh-min K.

Generic name
Vitamin K; phytonadione (vitamin K1) for clinical products
Drug class
Essential fat-soluble vitamin and coagulation-factor cofactor
Form
Food sources, dietary supplements, and prescription phytonadione oral or injectable products
Route
Oral dietary intake or supplement; oral or intravenous phytonadione in clinical use
Legal status
Available as an over-the-counter dietary supplement; phytonadione is also available as a prescription oral or injectable clinical product

Availability and supply rules vary by country

Trade names by country: United States

Australia: · Full directory

What Vitamin K; phytonadione (vitamin K1) for clinical products is and how it works

Vitamin K is an essential fat-soluble vitamin needed to make certain liver proteins involved in blood clotting. It acts as a cofactor in carboxylation reactions that enable certain proteins to bind calcium and activate the coagulation cascade. (1) (2) (3)

Vitamin K occurs naturally in foods, is available in dietary supplements, and phytonadione (vitamin K1) is used clinically for vitamin K deficiency and warfarin-related bleeding or over-anticoagulation. Severe deficiency can cause an increased prothrombin time and hemorrhagic events, although deficiency is rare in healthy people with normal dietary intake and gut function.

Mechanism of action: how Vitamin K; phytonadione (vitamin K1) for clinical products works

Vitamin K is a cofactor for gamma-glutamyl carboxylase-mediated carboxylation of glutamate residues to gamma-carboxyglutamate on certain proteins. This permits calcium-ion binding needed to activate the coagulation cascade. Warfarin blocks VKOR, preventing vitamin K recycling and reducing active clotting-factor production. (1) (2) (3)

What Vitamin K; phytonadione (vitamin K1) for clinical products is used for

Vitamin K deficiency states

Phytonadione (vitamin K1) is used clinically to manage vitamin K deficiency states and related coagulopathy. (2)

Warfarin-related bleeding or over-anticoagulation

Phytonadione is used clinically to manage bleeding related to warfarin toxicity or over-anticoagulation. Warfarin blocks vitamin K recycling and reduces production of active clotting factors; vitamin K administration reverses this anticoagulant effect. (2)

Dietary vitamin K intake

Vitamin K is obtained from food and may be obtained from dietary supplements. It is found particularly in leafy green and cruciferous vegetables, with smaller amounts in fish, liver, and eggs; intestinal bacteria also produce vitamin K. (3) (2)

Before taking Vitamin K; phytonadione (vitamin K1) for clinical products

Do not take / not appropriate for

  • Do not use vitamin K3 (menadione) clinically; it is highly toxic and is no longer used clinically. (vitamin K3 (menadione)) (2)
  • People with hypersensitivity to vitamin K require clinician assessment before receiving a vitamin K product. (vitamin K products) (2)

Tell your clinician about

  • Whether you take warfarin, because sudden changes in vitamin K consumption can change how well warfarin works.
  • Unusual bruising or bleeding, or a history of a bleeding disorder or coagulopathy.
  • Digestive-tract absorption problems or prolonged antibiotic use, which can be associated with vitamin K deficiency.
  • Any hypersensitivity to vitamin K.
  • Whether the patient is a neonate, has hereditary hypoprothrombinemia, or has renal impairment.
  • All medicines, supplements, and dietary products being used.
(2) (3)

How to take Vitamin K; phytonadione (vitamin K1) for clinical products

  • The appropriate vitamin K form, route, dose, and monitoring plan depend on whether it is being used as dietary intake, a supplement, or prescription phytonadione for a clinical bleeding or anticoagulation problem.
  • Use prescription phytonadione only under the direction of the responsible clinician.
  • Intravenous vitamin K1 requires slow administration and monitoring because serious reactions have been documented with this route.
  • If you take warfarin, discuss vitamin K food and supplement intake with the healthcare professional managing warfarin monitoring. Keep intake consistent from day to day rather than making sudden changes.
(2) (3)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3)

Missed dose

Instructions for a missed prescription phytonadione dose were not established in the sources reviewed. Contact the prescribing clinician or pharmacist for advice; do not take an extra dose without their direction.

Overdose

No Tolerable Upper Intake Level has been established for vitamin K, and no adverse effect was reported in the reviewed dietary-reference source for higher amounts from food or supplements at the dietary intake levels studied. Suspected prescription-product dosing errors or symptoms require prompt assessment by the prescribing service or poison-information service. (1)

Side effects

The reviewed source did not associate oral vitamin K1 with severe reactions. Safety concerns differ by vitamin K form and route: intravenous vitamin K1 has documented serious reactions, and vitamin K3 is highly toxic.

Bruising or bleeding associated with insufficient vitamin K

What to notice: People with insufficient vitamin K are more likely to have bruising and bleeding.

What to do: Discuss unexplained bruising or bleeding promptly with a clinician, particularly if taking warfarin or if there are digestive absorption concerns. (3)

Possible vitamin K deficiency

What to notice: New or unexplained bruising or bleeding.

What to do: Contact a clinician promptly for assessment. (3) (1)

Serious warnings

Serious reaction during intravenous vitamin K1 administration — emergency

Symptoms: Bronchospasm or cardiac arrest have been documented with intravenous vitamin K1 administration.

Action: This route requires slow infusion and monitoring. Seek emergency care for breathing difficulty or other signs of a severe reaction. (2)

Neonatal toxicity — urgent

Symptoms: In infants, toxicity has been associated with jaundice, hyperbilirubinemia, hemolytic anemia, and kernicterus.

Action: Neonates require cautious, clinician-directed use. The reviewed sources did not establish a specific neonatal dosing regimen. (2)

Vitamin K3 (menadione) toxicity — urgent

Symptoms: Vitamin K3 is described as highly toxic.

Action: Vitamin K3 is no longer used clinically. Seek prompt medical advice if there is concern about exposure to a vitamin K3 product. (2)

Interactions

Medicine or testEffectAction
WarfarinWarfarin blocks vitamin K epoxide reductase (VKOR), preventing vitamin K recycling and reducing active clotting-factor production. Vitamin K administration reverses warfarin's anticoagulant effect. Sudden changes in dietary vitamin K consumption can also change how well warfarin works.Keep vitamin K intake consistent from day to day and discuss food, supplement, and prescription vitamin K intake with the healthcare professional managing warfarin monitoring. (2) (3)
Prolonged antibiotic useProlonged antibiotic use is identified as a circumstance in which vitamin K deficiency can occur. Specific antibiotic interactions and mechanisms were not established in the sources reviewed.Tell a clinician about prolonged antibiotic use and any bruising or bleeding. (3)

Pregnancy, breastfeeding, kidney/liver function, age

Infants, children, and adolescents

Dietary adequate intake (AI) values are 2.0 micrograms/day from 0 to 6 months, 2.5 micrograms/day from 7 to 12 months, 30 micrograms/day at ages 1 to 3 years, 55 micrograms/day at ages 4 to 8 years, 60 micrograms/day at ages 9 to 13 years, and 75 micrograms/day at ages 14 to 18 years. Neonates require cautious, specific clinical use. A specific pediatric or neonatal phytonadione dosing regimen was not established in the sources reviewed. (1) (2)

Pregnancy and lactation

The dietary AI is 75 micrograms/day for pregnancy and lactation at ages 14 to 18 years and 90 micrograms/day at ages 19 to 50 years. Prescription phytonadione use in pregnancy or breastfeeding was not specifically established in the sources reviewed and requires clinician guidance. (1)

Adults

The dietary AI for adults aged 19 years and over is 120 micrograms/day for men and 90 micrograms/day for women. These are AIs, not RDAs, because data were insufficient to establish an Estimated Average Requirement. (1)

Renal impairment and hereditary hypoprothrombinemia

The reviewed source advises caution with vitamin K in renal impairment and hereditary hypoprothrombinemia. No impairment-specific dosing guidance was established in the sources reviewed. (2)

Monitoring

Before starting

  • Clarify whether vitamin K is being considered as dietary intake, a supplement, or prescription phytonadione for a deficiency or warfarin-related clinical problem.
  • Review warfarin use and current consistency of vitamin K intake.
  • Assess bleeding or bruising, digestive absorption concerns, prolonged antibiotic use, hypersensitivity, renal impairment, hereditary hypoprothrombinemia, and neonatal status where relevant.
  • For clinical coagulopathy management, assess prothrombin time and INR as directed by the responsible clinician.

During treatment

  • Monitor prothrombin time and INR when managing warfarin-related over-anticoagulation or coagulopathy.
  • Use slow infusion and monitoring when intravenous vitamin K1 is administered.
  • Reassess bleeding, bruising, treatment response, and warfarin monitoring needs where relevant.
  • No specific numeric INR target was established in the sources reviewed.
(2) (3)

Storage

Storage requirements for vitamin K supplements and prescription phytonadione products were not established in the sources reviewed. Follow the exact product packaging and pharmacist or clinician instructions.

Professional information

Clinician-facing context only. Use the current local product information, clinical protocol, route-specific administration requirements, and anticoagulation-management guidance.

All regions

Indication: Prescription phytonadione (vitamin K1) for vitamin K deficiency or warfarin-related coagulopathy

Dose summary: The reviewed StatPearls source describes adult oral phytonadione as typically 1 to 2 mg for routine correction and up to 5 to 10 mg for severe coagulopathy with elevated INR, with a described maximum of 25 mg. It describes intravenous dosing of 10 to 20 mg administered slowly over at least 30 minutes. Intravenous effect onset is described as 2 to 4 hours, with maximal effect at 6 to 12 hours; oral treatment takes approximately 24 hours to reach maximal effect. Pediatric and neonatal dosing, country-specific guidance, and specific INR targets were not established in the sources reviewed.

Renal context: Use with caution in renal impairment. No renal dose-adjustment recommendation was established in the sources reviewed. (2)

Mechanism of action

Hepatic guidance

Vitamin K is needed to make certain proteins in the liver that cause blood to clot. Hepatic-impairment dosing guidance was not established in the sources reviewed.

Overdose note

No Tolerable Upper Intake Level has been established. No adverse effect was reported for higher vitamin K amounts from food or supplements at the dietary intake levels studied. Evaluate suspected prescription-product dosing errors clinically. (1) (2) (3)

Frequently asked questions

What foods contain vitamin K?

Leafy green vegetables such as spinach, kale, and lettuce are important sources. Broccoli and Brussels sprouts also contain vitamin K, and smaller amounts occur in fish, liver, and eggs. Intestinal bacteria produce additional vitamin K. (3) (2)

What are the adult vitamin K intake values?

For adults aged 19 years and over, the adequate intake is 120 micrograms/day for men and 90 micrograms/day for women. These are adequate intake values rather than RDAs because there were insufficient data to establish an Estimated Average Requirement. (1)

Can I eat foods containing vitamin K while taking warfarin?

People taking warfarin need to keep vitamin K intake consistent from day to day because sudden changes can change how well warfarin works. Discuss vitamin K food and supplement intake with the healthcare professional managing warfarin monitoring. (3)

Does vitamin K treat osteoporosis?

Possible roles in preserving bone strength in older adults and in osteoporosis have been researched, but these are described in the reviewed sources as areas of investigation rather than established indications. (2) (3)

What is the mechanism of action of Vitamin K; phytonadione (vitamin K1) for clinical products?

Vitamin K is a cofactor for gamma-glutamyl carboxylase-mediated carboxylation of glutamate residues to gamma-carboxyglutamate on certain proteins. This permits calcium-ion binding needed to activate the coagulation cascade. Warfarin blocks VKOR, preventing vitamin K recycling and reducing active clotting-factor production. (1) (2) (3)

What is the generic name of Vitamin K?

The generic name is Vitamin K; phytonadione (vitamin K1) for clinical products. (1) (2) (3)

What class of drug is Vitamin K; phytonadione (vitamin K1) for clinical products?

Vitamin K is classed as: Essential fat-soluble vitamin and coagulation-factor cofactor. (1) (2) (3)

References

  1. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc — Vitamin K ChapterNational Academies Press (US); Institute of Medicine (US) Panel on Micronutrients · United States · accessed 2026-08-05 · source 1
  2. Vitamin KStatPearls Publishing · United States · accessed 2026-08-05 · source 2
  3. Vitamin K: MedlinePlus Medical EncyclopediaU.S. National Library of Medicine · United States · accessed 2026-08-05 · source 3

Brand names by country

Single-ingredient Vitamin K; phytonadione (vitamin K1) for clinical products names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Natural ClinicianNatural Clinician
  • The Vitamin ShoppeThe Vitamin Shoppe
  • Integrative TherapeuticsIntegrative Therapeutics
  • Vitamin WorldVitamin World
  • NatureSmartNatureSmart
  • HydroxycutHydroxycut
  • Terry NaturallyTerry Naturally
  • LifeSeasonsLifeSeasons
  • Protocol For Life BalanceProtocol For Life Balance
  • NOWNOW
View brands in additional countries.