Vitamin K2

• Postmenopausal bone support, typically alongside vitamin D3 and calcium
• Osteoporosis treatment in Japan (high-dose MK-4, a prescription indication there)
• Slowing arterial and coronary calcification (surrogate-endpoint, preliminary)
• Lowering undercarboxylated osteocalcin and matrix-Gla protein markers
• General dietary insurance where fermented-food K2 intake is low

Vitamin K2 (menaquinone) is a fat-soluble vitamin distinct from the more commonly recognized vitamin K1 (phylloquinone). Both are required for the gamma-carboxylation of glutamic acid residues in specific "Gla proteins", a post-translational modification that converts inactive precursor proteins to functional forms capable of binding calcium. The seventeen identified vitamin K-dependent proteins span coagulation (factors II, VII, IX, X, proteins C, S, Z, the basis of K1's well-known anticoagulation role), bone metabolism (osteocalcin in osteoblasts), vascular biology (matrix Gla protein in vascular smooth muscle), and other tissues (Gas6 in cellular signaling, periostin in connective tissue). The distinction between K1 and K2 lies in their tissue distribution and biological emphasis: K1 (phylloquinone, from green leafy vegetables) is preferentially used by liver for clotting factor synthesis and has short tissue half-life (~1-2 hours plasma half-life); K2 menaquinones (particularly MK-7, the long-chain form) have substantially extended half-life (~3 days for MK-7), reach extrahepatic tissues efficiently, and disproportionately support the bone and vascular Gla proteins. The two K2 forms with greatest clinical relevance are MK-4 (menatetrenone, short-chain menaquinone, plasma half-life ~1 hour) and MK-7 (menaquinone-7, long-chain, plasma half-life ~3 days). MK-4 is produced endogenously through tissue conversion of K1 and is the form used in Japanese osteoporosis pharmaceutical preparations (Menatetrenone, sold as Glakay) at high doses (45mg/day). MK-7 is produced through bacterial fermentation, naturally abundant in Japanese natto (fermented soybeans), and is the form increasingly used in modern Western K2 supplementation (90-180mcg/day) due to favorable pharmacokinetics. The mechanism of cardiovascular benefit centers on matrix Gla protein (MGP) in vascular smooth muscle: when K2-dependent, MGP inhibits arterial calcification; when K2-deficient (under-carboxylated MGP, dp-ucMGP), arterial calcification accelerates. The mechanism of bone benefit centers on osteocalcin in osteoblasts: K2 enables gamma-carboxylation of osteocalcin which then binds calcium and incorporates into bone matrix. The Rotterdam Study (Geleijnse 2004) provided the foundational observational cardiovascular evidence; subsequent intervention trials (notably Knapen 2015 in postmenopausal women) supported the cardiovascular and bone effects of long-term MK-7 supplementation.

Modern K2 supplementation centers on MK-7 at 90-180mcg/day, taken with a fat-containing meal to support absorption (vitamin K is fat-soluble). The pharmacokinetic advantage of MK-7, plasma half-life ~3 days versus ~1 hour for MK-4, supports once-daily dosing protocols. The Knapen trials (2013 bone, 2015 cardiovascular) used 180mcg MK-7 daily for 3 years; bone and arterial stiffness effects developed progressively over the 3-year follow-up rather than emerging quickly. The Japanese pharmaceutical MK-4 protocol uses substantially higher doses (45mg/day in 3 divided doses) for established postmenopausal osteoporosis; this pharmaceutical dose is not typical in Western supplement context and would require specialist coordination. Combination products with vitamin D3 (typically 100-200mcg MK-7 + 1000-5000 IU D3) provide mechanistically complementary support, D3 for calcium absorption, K2 for calcium routing to bone rather than vasculature. The critical dosing principle for users on warfarin: K2 supplementation will affect warfarin pharmacology and requires explicit coordination with prescribing physician for INR monitoring and warfarin dose adjustment. Users on DOACs (rivaroxaban, apixaban, dabigatran, edoxaban) are NOT affected by K2 in the same way since DOAC pharmacology is K-independent. There is no established Upper Limit for vitamin K (no documented toxicity at high doses); supplemental doses in the 200-500mcg range are well-tolerated.

AI adult men

120mcg/day (total K, mostly K1 in diet)

AI adult women

90mcg/day (total K)

Standard MK-7 supplementation

90-180mcg/day

Knapen trial dose (bone, cardiovascular)

180mcg MK-7/day

Japanese MK-4 pharmaceutical

45mg/day in 3 divided doses

Hemodialysis vascular calcification

360-720mcg MK-7/day

Combination with D3

100-200mcg MK-7 + 1000-5000 IU D3

Upper limit

No established UL

• MK-7 (Menaquinone-7) Bacterial Fermentation

  Rating: gold

  The dominant modern consumer K2 supplement form. Produced through bacterial fermentation (typically Bacillus subtilis var. natto). Plasma half-life ~3 days supports once-daily dosing. NattoPharma's MenaQ7 is the patented branded form used in most clinical trials (Knapen 2013, 2015). 90-180mcg/day is the standard supplementation dose. Trans-isomer specifically is the bioactive form; some products contain cis-isomers with limited bioactivity.

• MK-4 (Menatetrenone) Pharmaceutical High-Dose

  Rating: gold

  Japanese pharmaceutical form (Glakay, Menatetrenone) at 45mg/day for postmenopausal osteoporosis treatment. Substantial Japanese clinical evidence base; not widely available outside Japan as pharmaceutical. Short plasma half-life (~1 hour) requires divided dosing. Used in Japan as part of established osteoporosis treatment paradigm.

• MK-4 in Consumer Supplements (Lower Dose)

  Rating: good

  Consumer supplement MK-4 at 1.5-5mg/day. Substantially lower than Japanese pharmaceutical dose; clinical evidence for lower-dose MK-4 is thinner than for MK-7 or pharmaceutical MK-4. Some functional medicine protocols combine MK-4 with MK-7 to capture both short-chain and long-chain forms.

• MenaQ7 (NattoPharma Branded MK-7)

  Rating: gold

  Patented and clinically-trialed branded MK-7 form. The form used in Knapen 2013, 2015, and most major MK-7 clinical trials. Licensed to multiple supplement manufacturers; appears as ingredient identifier on labels. Premium pricing generally justified by clinical trial inheritance and quality verification.

• Vitamin K2 + Vitamin D3 Combinations

  Rating: gold

  Mechanistically complementary supplementation. D3 supports calcium absorption from gut; K2 directs calcium to bone (osteocalcin) and away from arterial walls (matrix Gla protein). The combination addresses calcium handling at both ends of the pathway. Common modern formulation (typically 100-200mcg MK-7 + 1000-5000 IU D3).

• Natto (Bacillus subtilis var. natto Fermented Soybeans)

  Rating: gold

  Traditional Japanese food and the highest natural dietary source of MK-7. A typical serving (40g natto) provides ~400mcg MK-7, substantially exceeding supplementation doses. Acquired taste; strong fermented flavor and characteristic stringy texture limit Western adoption. The Japanese cardiovascular and longevity advantages associated with natto consumption are partly attributed to MK-7 content.

• Multivitamin Vitamin K Content

  Rating: caution

  Most multivitamins include vitamin K but often as K1 (phylloquinone) at low doses (20-50mcg). Cardiovascular and bone evidence specifically supports K2 supplementation; multivitamin K1 content is not adequate substitute. Check labels for specific K form and dose.

• Vitamin K1 (Phylloquinone) Supplements

  Rating: caution

  K1 supplements address coagulation function and are used pharmaceutically as warfarin antidote and in vitamin K deficiency bleeding. For cardiovascular and bone outcomes, K2 forms are substantially better-evidenced. The Booth ECKO 2008 trial demonstrated K1 supplementation did not produce bone outcomes equivalent to K2 trials.

• Postmenopausal women (bone health)

  Strength of evidence for this group: modest

  Knapen 2013 RCT and subsequent work support MK-7 at 180mcg/day for 3 years improves bone mineral density at lumbar spine and femoral neck. Effect sizes modest but clinically meaningful. Reasonable component of comprehensive postmenopausal bone strategy alongside calcium, vitamin D3, exercise, and where indicated bisphosphonates.

• Cardiovascular calcification risk

  Strength of evidence for this group: modest

  Knapen 2015 RCT supports MK-7 at 180mcg/day for 3 years improving arterial stiffness measures. Mechanistically reasonable (matrix Gla protein activation). Effect sizes modest; reasonable as adjunct to comprehensive cardiovascular prevention. Not substitute for statins, blood pressure management, and lifestyle interventions in established cardiovascular disease.

• Hemodialysis patients (vascular calcification)

  Strength of evidence for this group: modest

  Caluwé 2014 and subsequent trials support MK-7 supplementation reducing dp-ucMGP and slowing vascular calcification in dialysis patients. Mechanistically compelling cohort (chronic kidney disease patients have substantial vascular calcification and elevated dp-ucMGP). Nephrology coordination for clinical implementation.

• Warfarin users

  Strength of evidence for this group: cautious

  CRITICAL CONTRAINDICATION CONSIDERATION. K2 supplementation can affect warfarin pharmacology, generally reducing anticoagulant effect (warfarin works as vitamin K antagonist). Users on warfarin should NOT initiate or modify K2 supplementation without explicit coordination with prescribing physician. INR monitoring with warfarin dose adjustment is required if K2 is to be added.

• Postmenopausal women on DOACs (rivaroxaban, apixaban)

  Strength of evidence for this group: cautious

  Direct oral anticoagulants (DOACs) are NOT vitamin K-dependent, K2 supplementation does not affect DOAC pharmacology in the way it affects warfarin. K2 supplementation may be reasonable for postmenopausal bone and cardiovascular indications in DOAC users. Coordinate with cardiology for clarity.

• Healthy adults (general bone/cardiovascular maintenance)

  Strength of evidence for this group: modest

  Reasonable component of comprehensive nutrition for users seeking bone and cardiovascular maintenance, particularly in combination with vitamin D3 and calcium. Effect sizes modest in healthy populations; the cohort with strongest evidence remains postmenopausal women and high-cardiovascular-risk populations.

• Children (vitamin K deficiency bleeding prevention)

  Strength of evidence for this group: strong

  Pediatric K1 administration at birth (intramuscular vitamin K) prevents vitamin K deficiency bleeding, established and recommended in essentially all developed-country pediatric protocols. K2 supplementation in healthy children beyond the newborn prophylaxis context is not standard practice; specialist coordination if pursuing.

• Pregnancy and lactation

  Strength of evidence for this group: cautious

  Limited systematic safety data for high-dose K2 supplementation in pregnancy and lactation. Standard prenatal vitamin K content (typically as K1) is established. High-dose K2 supplementation outside specialist guidance not recommended.

• Vitamin D3

  Interaction: synergy

  The signature K2 pairing. D3 supports intestinal calcium absorption; K2 directs absorbed calcium to bone (osteocalcin activation) and away from arterial walls (matrix Gla protein activation). Mechanistically elegant complementarity; modern combination products (typically MK-7 + D3) are common and reasonable.

• Calcium

  Interaction: synergy

  D3 + K2 + calcium represents the comprehensive bone supplementation approach. K2 specifically addresses the concern that calcium supplementation without adequate K2 status may produce arterial calcification rather than bone deposition.

• Warfarin

  Interaction: avoid

  CRITICAL INTERACTION. Vitamin K2 supplementation will affect warfarin pharmacology, reducing anticoagulant effect (warfarin is a vitamin K antagonist). Users on warfarin should NOT initiate K2 without explicit coordination with prescribing physician. INR monitoring and warfarin dose adjustment required.

• Direct Oral Anticoagulants (DOACs)

  Interaction: neutral

  Rivaroxaban, apixaban, dabigatran, edoxaban work through K-independent mechanisms (direct factor Xa or thrombin inhibition). K2 supplementation does NOT affect DOAC pharmacology in the way it affects warfarin. Safe to combine with appropriate clinical awareness.

• Bisphosphonates (Alendronate, etc.)

  Interaction: synergy

  Both target bone health through different mechanisms. K2 supports osteocalcin-mediated bone matrix incorporation; bisphosphonates inhibit osteoclast-mediated bone resorption. Mechanistically complementary; reasonable combination in postmenopausal osteoporosis management.

• Magnesium

  Interaction: synergy

  Common cardiovascular and bone protocol combination. Magnesium supports calcium handling, cardiovascular function, and bone matrix formation through distinct mechanisms from K2. Reasonable comprehensive bone and cardiovascular nutrition.

• Statins

  Interaction: neutral

  Some theoretical interaction proposed (statins may modestly reduce K2-dependent protein carboxylation) but clinical relevance not established. Generally compatible combination; standard cardiovascular protocols often include both.

• Antibiotics (long-course)

  Interaction: caution

  Prolonged broad-spectrum antibiotics can reduce gut bacterial K2 production (endogenous gut microbial K2 contribution to K status). Supplemental K2 during prolonged antibiotic courses is reasonable.

• Bile Acid Sequestrants (Cholestyramine)

  Interaction: caution

  Reduce absorption of fat-soluble vitamins including K. Take K2 supplements at separate times from bile acid sequestrants; clinically relevant interaction for users on these lipid-lowering agents.

Look for: specific K2 form disclosed (MK-7 or MK-4); trans-isomer specification for MK-7 (bioactive form, not cis-isomer); MenaQ7 ingredient identifier for clinical-trial-form MK-7; clear dose disclosure (90-180mcg MK-7 is standard); combination with vitamin D3 if comprehensive bone/cardiovascular protocol desired; USP or NSF third-party verification; reasonable price (premium pricing for branded MenaQ7 is generally justified; very high pricing without specific quality differentiation is suspect). Avoid: proprietary "bone health" blends obscuring K2 dose; K1 (phylloquinone) marketed as substitute for K2 cardiovascular/bone benefits (different evidence base); MK-7 products without trans-isomer specification; products from manufacturers without third-party testing disclosure; combination with anticoagulants without prescribing physician awareness.

Vitamin K's discovery story begins in 1929 with Danish biochemist Henrik Dam at the University of Copenhagen. Working on cholesterol metabolism in chickens fed fat-free diets, Dam observed unexplained hemorrhagic disease that was not corrected by any known nutrient. He hypothesized a previously-uncharacterized fat-soluble vitamin and named it "Koagulation vitamin" (vitamin K), establishing the naming convention. American biochemist Edward Doisy isolated and characterized the chemical structures of both K1 (phylloquinone, from alfalfa) and K2 (menaquinone, from bacterial sources) through the 1930s. Dam and Doisy shared the 1943 Nobel Prize in Physiology or Medicine for vitamin K discovery and characterization. The coagulation factor characterization developed through mid-20th century work. K-dependent gamma-carboxylation of factors II, VII, IX, X (and proteins C, S, Z) established the mechanism. Warfarin was developed initially as rat poison (1948) and subsequently as anticoagulant medication (1954), exploiting vitamin K antagonism for therapeutic anticoagulation. The clinical understanding of warfarin-K interactions has been a major focus of clinical practice ever since. The extrahepatic vitamin K story developed substantially later. Osteocalcin (the bone Gla protein) was characterized in 1975-1980; matrix Gla protein in vascular tissue was characterized in 1983-1989. The realization that these Gla proteins required vitamin K for activation, but that the liver-centric K1 metabolism did not efficiently support extrahepatic Gla proteins, established the K2 differential biological emphasis. The Japanese pharmaceutical era began in the 1990s with the development of menatetrenone (MK-4) for postmenopausal osteoporosis at 45mg/day. Substantial Japanese clinical evidence accumulated through Akiba and colleagues; Glakay became established pharmaceutical practice in Japanese osteoporosis medicine. The pharmaceutical use case has not been adopted in Western practice, partly due to dose differences (45mg pharmaceutical vs micrograms in Western supplements) and partly due to evidence-base differences. The cardiovascular K2 story began with the Rotterdam Study (Geleijnse 2004), the foundational observational evidence linking K2 dietary intake to reduced cardiovascular mortality, all-cause mortality, and severe aortic calcification. The observational signal was substantial and largely K2-specific (no equivalent association for K1). The mechanism, matrix Gla protein activation in vascular smooth muscle, provided biological plausibility. Subsequent marker work (Beulens 2008 dp-ucMGP cardiovascular outcomes) supported the mechanism. The modern MK-7 supplement era developed through the 2010s with the Knapen trials in postmenopausal women, bone (2013 Osteoporosis International) and cardiovascular (2015 Thrombosis and Haemostasis), using 180mcg MK-7 daily for 3 years. These interventional trials supported modest but meaningful effects on intermediate endpoints (bone mineral density, arterial stiffness). The MenaQ7 branded form from NattoPharma became the clinical-trial standard. The consumer supplement era expanded substantially through the late 2010s and 2020s. K2 supplementation became prominent in functional medicine and longevity circles, often in combination with D3 in modern bone and cardiovascular protocols. The category has grown to substantial commercial scale, with brand differentiation around MK-7 vs MK-4, trans-isomer specification, and combination products with D3 and other cofactors. The mainstream cardiology and orthopedics integration has been slower, most guideline-directed therapy does not include K2 routinely, though awareness has increased substantially.

1. 1929-1943Dam discovers vitamin K; Doisy characterizes K1 and K2 structures (Nobel 1943)
2. 1948-1954Warfarin developed as anticoagulant exploiting K antagonism
3. 1975-1980Osteocalcin (bone Gla protein) characterized
4. 1983-1989Matrix Gla protein (MGP) characterized in vascular tissue
5. 1990sJapanese pharmaceutical menatetrenone (Glakay) MK-4 for osteoporosis
6. 2004Rotterdam Study cardiovascular evidence (Geleijnse)
7. 2008Beulens dp-ucMGP cardiovascular outcomes; Booth ECKO K1 bone trial (negative)
8. 2013Knapen postmenopausal bone trial (180mcg MK-7)
9. 2014Caluwé hemodialysis vascular calcification trial
10. 2015Knapen postmenopausal cardiovascular trial (arterial stiffness)
11. 2017Schwalfenberg comprehensive K2 review consolidates framework
12. 2020sMK-7 + D3 combination products dominate consumer bone/cardiovascular category

• Whether the cardiovascular benefits of MK-7 supplementation will translate to hard cardiovascular endpoints (MI, stroke, mortality) in larger and longer trials, current evidence centers on intermediate endpoints (arterial stiffness, calcification scores).
• Whether the bone benefits of MK-7 supplementation will translate to fracture endpoint reductions in larger trials, current evidence centers on bone mineral density.
• Whether MK-4 and MK-7 have meaningfully different clinical effects beyond their pharmacokinetic differences, head-to-head trials are limited.
• Whether the Japanese pharmaceutical high-dose MK-4 approach (45mg/day) has applications in Western osteoporosis management, current Western practice favors lower-dose MK-7.
• Whether dp-ucMGP marker assessment should be standardized in cardiovascular risk evaluation, currently research-grade rather than routine clinical use.
• Whether K2 has applications in chronic kidney disease progression beyond the vascular calcification evidence in dialysis patients.
• How best to integrate K2 supplementation with anticoagulation management, current guidance is binary (avoid with warfarin; safe with DOACs) but more nuanced approaches may emerge.
• Whether endogenous gut microbial K2 production should be considered in supplementation guidance, gut microbiome variability may produce individual K status variation independent of dietary intake.

Universally available globally as dietary supplement. Legal under DSHEA in the United States and equivalent supplement regulations in most jurisdictions. Not on WADA prohibited list. Pharmaceutical menatetrenone (Glakay) is available by prescription in Japan for osteoporosis; not widely available outside Japan as pharmaceutical product. MK-7 supplements (particularly MenaQ7 branded) are widely available from major supplement manufacturers including Thorne, Pure Encapsulations, Life Extension, Solgar, NOW Foods, Designs for Health, Jarrow Formulas. Combination D3 + K2 products are particularly common in modern bone health categories. Natto is widely available in Japanese grocery stores globally; specialty Asian markets stock natto in most major Western cities. Production of synthetic K2 (MK-4) is well-established; bacterial fermentation K2 (MK-7) is dominated by NattoPharma's MenaQ7 patent and licensed manufacturers.

Status current as of July 2026. Regulatory positions change, sometimes quickly.

Status

Fat-soluble vitamin

Two main forms

K1 (phylloquinone), K2 (menaquinone)

K2 subtypes

MK-4 through MK-13 (MK-4 and MK-7 most relevant)

MK-7 plasma half-life

~3 days

MK-4 plasma half-life

~1 hour

AI adult men

120mcg/day (total K, mostly K1 in diet)

What follows is unfinished work on our side, not a finding about Vitamin K2. A short entry is not a safe entry.

• Cost and market. We have not documented what it sells for or who sells it.
• Supply chain. We have not mapped where it is made.
• Who uses it. We have not documented the user groups.
• What could change. No forward-looking summary yet.
• How it compares. We have not set it against the alternatives.
• Children and teenagers. We have not checked what is known about younger people.
• Where we land. We have not taken a position on this yet.