Vitamin K2 (MK-7 vs MK-4)
Summary
Vitamin K2 supplements mainly contain MK-7 or MK-4. MK-7 lasts much longer in blood, while MK-4 at food-level amounts was not detectable. One 3-year trial found less bone loss with 180 mcg/day MK-7 (grade C); 45 mg/day MK-4 did not change bone density in North American women. Vitamin K affects warfarin.
Key facts
- MK-7 (menaquinone-7, often from natto) and MK-4 (menatetrenone); K1 (phylloquinone) for context[1]
- MK-7 has a very long half-life and accumulates 7–8-fold with daily intake; MK-4 at 60–420 mcg was not detectable in blood[7][6]
- Bone density loss with MK-7 ↑ less loss (C); bone density with 45 mg MK-4 ↔ (no effect); arterial stiffness with MK-7 ↑ (C); coronary calcium score progression (any vitamin K) ↑ slower (C)[2][3][5][4]
- AI 120 mcg (men), 90 mcg (women); no UL[1]
- Warfarin and similar anticoagulants (serious); antibiotics, bile acid sequestrants and orlistat can lower vitamin K status[1][7]
- 1 meta-analysis and 3 randomized trials, plus 1 meta-analysis and 2 absorption studies cited as supporting evidence[4][2][3][5][8][6][7]
- 4 graded human outcomes on this page
- October 8, 2026
How it works
EstablishedVitamin K is a coenzyme for the enzyme that activates (carboxylates) clotting factors, osteocalcin in bone and matrix Gla protein in blood vessels (established). Lower undercarboxylated osteocalcin and dp-ucMGP with supplementation are measured in trials; whether this translates into stronger bones or fewer vascular problems is proposed.[1][3][5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Heart | Grade C | Improved | Meta-analysis · n = 1,533 · 2023 | 2 rows |
| Bones & joints | Grade C | Improved | RCT · n = 244 · 2013 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Coronary artery calcium score progression (any vitamin K form) | Improved | Grade C | Meta-analysis · n = 1,533 · 2023 14 RCTs in adults (populations not broken down in the abstract) Form: vitamin K (forms not specified in abstract) · Dose: Varied across trials · Duration: Varied across trials Coronary artery calcium scores progressed less with vitamin K (MD -17.37; p = 0.04) and dp-ucMGP fell; adverse events did not differ from control. | 37252246 (opens PubMed)Source [4] |
| Age-related bone density loss with MK-7 | Improved | Grade C | RCT · n = 244 · 2013 Healthy postmenopausal women Form: MK-7 · Dose: 180 mcg/day · Duration: 3 years MK-7 improved vitamin K status and reduced the decline in bone mineral content and density at the lumbar spine and femoral neck, but not the total hip; bone strength indices and vertebral height loss in the lower thoracic spine also favored MK-7. | 23525894 (opens PubMed)Source [2] |
| Arterial stiffness with MK-7 | Improved | Grade C | RCT · n = 244 · 2015 Healthy postmenopausal women (same cohort as the 3-year bone trial) Form: MK-7 · Dose: 180 mcg/day · Duration: 3 years Carotid-femoral pulse wave velocity and stiffness index β decreased versus placebo; more local stiffness measures improved in women with higher baseline stiffness. dp-ucMGP fell 50% versus placebo; inflammation and endothelial markers did not change. | 25694037 (opens PubMed)Source [5] |
| Bone density with high-dose MK-4 (or K1) | No effect | No effect | RCT · n = 381 · 2009 Healthy postmenopausal North American women without osteoporosis, all on calcium and vitamin D3 Form: MK-4 (menatetrenone) or phylloquinone (K1) vs placebo · Dose: MK-4 45 mg/day; K1 1 mg/day · Duration: 12 months Both forms lowered undercarboxylated osteocalcin but did not change bone turnover markers, lumbar spine or hip bone density, or hip geometry. | 19113922 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| MK-7 (menaquinone-7) | Varies[9] | Well absorbed (peak about 4–6 hours) with a very long half-life, giving stable blood levels that accumulate 7–8-fold with daily intake. 420 mcg was detectable for up to 48 hours.[7][6][1] | No adverse effects from vitamin K in food or supplements reported by the FNB; no UL.[1] | Bone density loss and arterial stiffness (180 mcg/day, 3 years) |
| MK-4 (menatetrenone) | Varies[9] | At nutritional amounts (420 mcg once, or 60 mcg/day for 7 days), MK-4 was not detectable in blood, while MK-7 was. Studied pharmacologically at 45 mg/day.[6][1] | No adverse effects reported by the FNB at food or supplement intakes; 45 mg/day was given for 12 months in a North American trial.[1][3] | Bone density (45 mg/day); used as an osteoporosis medicine in Japan |
Studied doses
Doses studied in human trials ranged from 180 mcg/day of MK-7 to 45 mg/day (45,000 mcg) of MK-4, for 12 months to 3 years. The two forms were studied at very different amounts, so microgram figures are not interchangeable between them.[2][3]
Intake reference: Adult AI for vitamin K (all forms): 120 mcg/day for men and 90 mcg/day for women, including pregnancy and breastfeeding. No UL has been set.[1] No UL: the FNB found no adverse effects from vitamin K in food or supplements. The interaction with warfarin is the main safety concern. NIH ODS fact sheet (updated March 29, 2021).
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Warfarin and similar anticoagulantsNIH fact sheetSerious, potentially dangerous interaction: vitamin K counteracts these drugs, so sudden changes in vitamin K intake can change their effect. A study of MK-7 warned that 50 mcg/day or more may interfere with oral anticoagulant treatment in a clinically relevant way.[1][7]
Medicines that can lower levels
- AntibioticsNIH fact sheetCan destroy vitamin K-producing gut bacteria and may lower vitamin K status, especially with prolonged use and poor intake.[1]
- Bile acid sequestrantsNIH fact sheetCan reduce absorption of vitamin K and other fat-soluble vitamins.[1]
- OrlistatNIH fact sheetReduces absorption of fat-soluble vitamins including vitamin K; orlistat with warfarin might markedly raise prothrombin time.[1]
Who should be careful
- People on warfarin or similar anticoagulants
- Do not start, stop or change a vitamin K2 supplement without your prescriber. Even 50 mcg/day of MK-7 may affect anticoagulation.[1][7]
- Pregnancy and breastfeeding
- The AI is 90 mcg/day for adults 19+ in pregnancy and breastfeeding; no UL is set. Pregnancy-specific trial data for K2 supplements are not in our sources.[1]
- Malabsorption or bariatric surgery
- People with malabsorption conditions or after bariatric surgery may have low vitamin K status and may need clinician monitoring.[1]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Articles about Vitamin K2 (MK-7 vs MK-4)
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
Is MK-7 better than MK-4?
They behave differently. MK-7 stays in the blood much longer and builds up with daily use, while MK-4 at food-level amounts (60–420 mcg) was not detectable in blood. The bone trials used very different amounts: 180 mcg/day MK-7 versus 45 mg/day MK-4. No trial has compared them head to head on bone outcomes.[7][6][2][3]
Does vitamin K2 help bones?
Evidence is limited and mixed. One 3-year trial found 180 mcg/day MK-7 slowed bone density loss in postmenopausal women, but 45 mg/day MK-4 did not change bone density in North American women, and a 2019 meta-analysis found no effect on bone density across vitamin K trials.[2][3][8]
Does vitamin K2 reduce arterial calcification?
Possibly, but evidence is weak. A 2023 meta-analysis of 14 trials (n=1,533) found slower progression of coronary artery calcium scores with vitamin K (borderline significance), without separating vitamin K forms in the abstract. One 3-year MK-7 trial found reduced arterial stiffness.[4][5]
Why is vitamin K2 often paired with vitamin D3?
Both are involved in calcium handling: vitamin K activates osteocalcin in bone and matrix Gla protein in vessel walls, and vitamin D raises calcium absorption, so they are often marketed together. ODS cautions that giving vitamin D and calcium alongside vitamin K may explain why some bone trials show benefits and others do not.[1][10]
Can I take vitamin K2 with blood thinners?
Only with your prescriber's oversight if you take warfarin or a similar vitamin K antagonist: ODS calls the interaction serious, and an MK-7 study warned that 50 mcg/day or more may interfere with anticoagulation. Ask a pharmacist about other blood thinners.[1][7]
Sources
- [1]Vitamin K: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2021. fact-sheet
- [2]Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women.. Osteoporos Int, 2013. RCT
- [3]Vitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American women.. J Bone Miner Res, 2009. RCT
- [4]Vitamin K supplementation and vascular calcification: a systematic review and meta-analysis of randomized controlled trials.. Front Nutr, 2023. meta-analysis
- [5]Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial.. Thromb Haemost, 2015. RCT
- [6]Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women.. Nutr J, 2012. PK-study
- [7]Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7.. Blood, 2007. PK-study
- [8]Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials.. Osteoporos Int, 2019. meta-analysis
- [9]Menaquinone-7 (CID 5287554) and menatetrenone/MK-4 (CID 5282367): molecular weights. PubChem, NCBI, 2026. database
- [10]Vitamin D: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. fact-sheet
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.