Vitamins
Vitamin K
Vitamin K is an essential, fat-soluble vitamin. Your body needs it to activate proteins involved in blood clotting and bone metabolism.
Vitamin K describes a family of related compounds rather than a single substance. Its main forms are vitamin K1 (phylloquinone) and vitamin K2, a group of menaquinones such as MK-4 and MK-7. Your body uses vitamin K as a cofactor for an enzyme that enables certain proteins to function. Vitamin K is a nutrient found in foods, not a food or botanical extract; K1 and K2 are specific forms, not interchangeable names for the whole vitamin K family.
Vitamin K: important for blood clotting and bones
Vitamin K is an essential, fat-soluble vitamin. Your body uses it to enable certain proteins to function, including proteins involved in blood clotting and bone metabolism.
K1 and K2: one family, different forms
Vitamin K is not a single substance. Vitamin K1, also called phylloquinone, occurs particularly in green leafy vegetables and is the main dietary form of vitamin K in Europe. Vitamin K2 refers to a group of menaquinones, such as MK-4 and MK-7. These occur in animal products and fermented foods. Their forms and amounts depend partly on production and fermentation conditions, so fermented foods do not all provide the same amount of K2.
What vitamin K does in your body
Vitamin K contributes to normal blood clotting and to the maintenance of normal bones. Both health claims are authorised in the EU (Commission Regulation (EU) No 432/2012, Annex). They may be used for foods that meet at least the conditions for a source of vitamin K. This does not mean that additional supplements further improve clotting, prevent fractures or treat osteoporosis.
Absorption and possible shortfalls
Intestinal absorption of vitamin K1 depends partly on dietary fat, bile salts, pancreatic function and meal composition. Clinically significant deficiency is rare in healthy adults. People with malabsorption disorders are at higher risk; discuss your vitamin K status with your clinician if this applies to you. Newborns are a particular risk group: vitamin K prophylaxis protects against vitamin K deficiency bleeding. Maternal intake does not replace this prophylaxis.
- K2 requirements and gut bacteria — insufficient evidence: Gut bacteria produce K2 forms, but their absorption and contribution to vitamin K status are unclear. Evidence is also insufficient to establish a separate K2 intake reference value.
- Cardiovascular health — limited evidence: Supplements can improve vitamin K status biomarkers. Whether they slow vascular calcification is uncertain, and protection against heart attacks or strokes has not been established.
- Blood glucose control — limited evidence: Supplements may improve some measures in adults with prediabetes or type 2 diabetes. Small, varied trials and inconsistent results do not support a recommendation to use vitamin K to treat diabetes.
More is not automatically better
No tolerable upper intake level (UL) has been established for vitamin K because adequate data are lacking. This does not mean that unlimited doses are safe. Evidence gaps remain, particularly for long-term high-dose use. If you are pregnant or breastfeeding, use high-dose products only after medical advice.
How nutrition works
Blood coagulation
Bone health
Cardiovascular health
Vitamin K supplements can improve vitamin K status biomarkers, but whether they slow vascular calcification is uncertain. [3]
Glycaemic control
Vitamin K supplements may improve some measures of blood glucose control in adults with prediabetes or type 2 diabetes, but the benefit remains uncertain. [4]
Statements & evidence
Vitamin K is a family of fat-soluble compounds. Naturally occurring forms include phylloquinone (K1) and menaquinones (K2). [5][6]
K2 refers to a group of different menaquinones, not a single substance.
Vitamin K1 occurs particularly in green leafy vegetables and is the main dietary form of vitamin K in Europe. K2 forms occur in animal products and fermented foods. [5][6]
The menaquinone forms and amounts in a food depend partly on production and fermentation conditions. Fermented foods therefore cannot be assigned a single common K2 content.
EFSA sets an Adequate Intake of 70 µg of phylloquinone (vitamin K1) per day for adults, including during pregnancy and breastfeeding. [6]
This reference value is not an individual supplement recommendation. EFSA uses an Adequate Intake because the evidence is insufficient to derive an Average Requirement and Population Reference Intake. It is not a separately established K2 requirement.
The EU Nutrient Reference Value for vitamin K on food labels is 75 µg. [7][6]
This value is used for nutrition labelling, including percentage reference-value declarations. It is distinct from EFSA's Adequate Intake and does not describe your individual requirement.
Intestinal absorption of vitamin K1 depends partly on dietary fat, bile salts and pancreatic function. [6]
The food and the composition of the meal also influence absorption. A single absorption percentage therefore cannot reliably be applied to all vitamin K-containing foods.
Clinically significant vitamin K deficiency is rare in healthy adults. Risk is higher in newborns without vitamin K prophylaxis and in people with malabsorption disorders. [8]
The statement about rarity applies to healthy adults, not to every age or risk group. If you have a malabsorption disorder, discuss your vitamin K status with your clinician.
Vitamin K can affect the action of vitamin K antagonists such as warfarin. If you take these medicines, keep your vitamin K intake consistent and discuss changes with your prescriber. [8]
This applies to vitamin K from foods and supplements. You do not need to avoid vitamin K-containing vegetables altogether; consistency matters. Do not start or stop a vitamin K supplement without discussing it with your prescriber.
The available evidence is insufficient to establish a separate EFSA intake reference value for vitamin K2. [6]
EFSA's intake reference concerns phylloquinone (K1). It cannot be used to derive a separate daily K2 dose.
Gut bacteria produce menaquinones (vitamin K2 forms), but their absorption and contribution to vitamin K status remain unclear. [6]
Bacterial production alone does not establish that it supplies your body with enough vitamin K.
The EU Scientific Committee on Food could not establish a numerical tolerable upper intake level for vitamin K because suitable data were insufficient. [9][8]
The absence of an upper limit does not mean that unlimited supplementation is safe. In particular, if you take a vitamin K antagonist, discuss vitamin K supplements with your prescriber before using them.
Safety information
Upper level · Adults
BfR recommendations for supplements
BfR recommends maximum amounts of 80 µg vitamin K1 or 25 µg vitamin K2 per supplement's recommended daily dose. These are risk-management recommendations, not total-intake ULs or a guarantee of compatibility with vitamin K antagonists. [11]
Interaction
Important interaction with vitamin K antagonists
If you take warfarin, phenprocoumon, acenocoumarol or another vitamin K antagonist, keep your vitamin K intake reasonably consistent. You do not generally need to avoid vitamin K-rich vegetables. Discuss starting, stopping or changing K1 or K2 supplements with your treatment team because they can alter anticoagulation. [8][11]
Caution
Not all anticoagulants are affected
The vitamin K-related dietary advice for warfarin does not usually apply to apixaban, dabigatran, edoxaban or rivaroxaban. If you take one of these medicines, still check new supplements with your clinician or pharmacist. [12]
Interaction
Antibiotics can affect vitamin K status
Prolonged antibiotic treatment combined with poor food intake can increase the risk of inadequate vitamin K status. Some cephalosporins also inhibit vitamin K activity. Supplementation is not routinely needed; have any possible need assessed clinically. [8]
Interaction
Some medicines reduce absorption
Orlistat and the bile acid sequestrants cholestyramine and colestipol can reduce vitamin K absorption. During prolonged use, vitamin K status may need assessment, especially if you also take a vitamin K antagonist. Do not independently add vitamin K to compensate for this interaction. [8]
Side effect
Injections have separate risks
Severe anaphylactoid reactions, local pain, inflammation and venous irritation are documented with medicinal vitamin K1 injections. Rapid intravenous administration can cause severe circulatory reactions. These risks depend on the product and its administration and should not be attributed to vitamin K in food. [13][14]
Contraindication
Allergy to medicinal product ingredients
A vitamin K1 medicine must not be used in someone with known hypersensitivity to its active ingredient or an excipient. This contraindication concerns the specific product and is not a general reason to avoid foods containing vitamin K. [14]
Caution
High-dose products during pregnancy and breastfeeding
If you are pregnant or breastfeeding, use high-dose vitamin K products only after medical advice. High-dose supplement safety is not adequately established, and medicinal K1 during pregnancy requires a benefit–risk assessment. Maternal intake does not replace newborn vitamin K prophylaxis. [14][13][6]
Side effect
Vitamin K prophylaxis in newborns
Routine vitamin K injection in newborns is considered safe and protects against vitamin K deficiency bleeding. Injection-site pain, bruising or swelling can occur. Larger studies have not supported the previously suspected link with childhood cancer. [15]
Caution
K3 is not equivalent to K1 and K2
The safety assessment for K1 and K2 does not apply to menadione (vitamin K3). NIH ODS reports liver-cell damage in laboratory studies and states that menadione is no longer used in dietary supplements or fortified foods. [8]
Frequently asked questions
What does your body need vitamin K for?
Vitamin K contributes to normal blood clotting and the maintenance of normal bones. This does not mean that additional supplements prevent fractures or treat osteoporosis.
What is the difference between vitamin K1 and K2?
Vitamin K1 is called phylloquinone and occurs particularly in green leafy vegetables. Vitamin K2 refers to a group of menaquinones, including MK-4 and MK-7, found in animal products and fermented foods.
How much vitamin K do you need each day?
EFSA sets an Adequate Intake of 70 µg of vitamin K1 per day for adults, including during pregnancy and breastfeeding. This is not an individual supplement recommendation; no separate EFSA intake reference value has been established for K2.
Do you need to avoid vitamin K-rich vegetables if you take anticoagulants?
If you take a vitamin K antagonist such as warfarin or phenprocoumon, you do not generally need to avoid vitamin K-rich vegetables, but you should keep your intake reasonably consistent. Discuss starting, stopping or changing K1 or K2 supplements with your treatment team. This vitamin K-related dietary advice does not usually apply to direct oral anticoagulants such as apixaban or rivaroxaban.
Can too much vitamin K be harmful?
No tolerable upper intake level has been established for vitamin K because adequate data are lacking. This does not mean that unlimited doses are safe, particularly as evidence on long-term high-dose use is limited. Vitamin K supplements can also alter the action of vitamin K antagonists.
More entries
Folate
Folate is a water-soluble B vitamin. Its active forms take part in DNA synthesis and amino-acid metabolism.
Vitamin A
Vitamin A is an essential, fat-soluble vitamin. Your diet supplies it as preformed vitamin A or as precursors from plant foods.
Vitamin B12
Vitamin B12 is an essential, water-soluble vitamin. Your body needs it for normal nervous-system function, red blood cell formation and DNA synthesis.
Vitamin C
Vitamin C is an essential, water-soluble vitamin that you need to obtain through your diet. Its principal chemical form is L-ascorbic acid.
Vitamin D
Vitamin D is a fat-soluble vitamin. The term mainly covers vitamins D₂ and D₃; your body can produce D₃ in the skin through exposure to UVB radiation.
Vitamin B6
Vitamin B6 is a water-soluble vitamin. Its active forms support many metabolic processes, particularly amino-acid metabolism.
Sources
- 01EFSA Journal · 2009Scientific Opinion on the substantiation of health claims related to vitamin K and maintenance of bone, blood coagulation, and function of the heart and blood vessels pursuant to Article 13(1) of Regulation (EC) No 1924/2006DOI 10.2903/j.efsa.2009.1228
- 02European Commission · 2012Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, other than those referring to the reduction of disease risk and to children's development and healthOpen source
- 03Frontiers in Nutrition · 2023Vitamin K supplementation and vascular calcification: a systematic review and meta-analysis of randomized controlled trialsDOI 10.3389/fnut.2023.1115069PubMed 37252246
- 042026The Differential Effects of Vitamin K Across Glycaemic Outcomes in Prediabetes and Type 2 Diabetes MellitusOpen source
- 05European Food Safety Authority · 2017Dietary Reference Values for nutrients: Summary reportOpen source
- 06EFSA Journal · 2017Dietary reference values for vitamin KEFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)DOI 10.2903/j.efsa.2017.4780
- 07European Parliament and Council of the European Union · 2011Regulation (EU) No 1169/2011 on the provision of food information to consumersOpen source
- 08National Institutes of Health, Office of Dietary SupplementsVitamin K - Health Professional Fact SheetOpen source
- 09European Commission — Scientific Committee on Food · 2003Opinion of the Scientific Committee on Food on the Tolerable Upper Intake Level of Vitamin KScientific Committee on FoodOpen source
- 10European Food Safety AuthoritySummary tables of tolerable upper intake levels for vitamins and minerals, version 8Open source
- 11German Federal Institute for Risk Assessment (BfR)Proposed maximum levels for the addition of vitamin K to foods including food supplementsOpen source
- 12NHSAnticoagulant medicines - ConsiderationsOpen source
- 13Agencia Española de Medicamentos y Productos Sanitarios (AEMPS)Ficha técnica: Konakion 10 mg/ml solución oral/solución inyectableOpen source
- 14Health Products Regulatory Authority (HPRA) · 2023Konakion MM: adult medicinal product informationOpen source
- 15Centers for Disease Control and Prevention (CDC)Frequently Asked Questions About Vitamin K Deficiency BleedingOpen source
- 162020Correction to Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trialsPubMed 32965511Open source
- 172019Effect of Vitamin K on Bone Mineral Density and Fractures in Adults: An updated systematic review and meta-analysis of randomised controlled trialsOpen source
- 182024Effects of vitamin K supplementation on bone mineral density at different sites and bone metabolism in the middle-aged and elderly population: a meta-analysis and systematic review of randomized controlled trialsOpen source