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Limited evidenceHeart & metabolic

Vitamin K2 (MK-7)

MK-7 reliably improves vitamin K biomarkers — it carboxylates osteocalcin and matrix Gla protein exactly as advertised. But the hard-outcome evidence is thin, and the best-powered trial of the vascular calcification claim was completely flat. Good mechanism, unproven benefit.

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What the science says

  • Slows age-related bone loss in postmenopausal women Moderate evidence

    In the largest MK-7 bone trial, 244 healthy postmenopausal women took 180 mcg/day or placebo for three years. MK-7 significantly reduced the age-related decline in bone mineral content and BMD at the lumbar spine and femoral neck (but not total hip) and reduced loss of vertebral height in the lower thoracic region. Fractures were not an endpoint, and this remains one trial in one population.

  • Did not slow vascular calcification in the trial built to test it Limited evidence

    The AVADEC trial gave 720 mcg/day MK-7 plus 25 mcg vitamin D to 365 elderly men with aortic valve calcification scores above 300 AU for two years. Despite a large fall in dephospho-uncarboxylated MGP (-212 pmol/L), progression of aortic valve calcification was identical (mean difference 17 AU, 95% CI -86 to 53, P=0.64), as were aortic valve area (P=0.78) and peak jet velocity (P=0.21). The biomarker moved; the artery did not.

  • Modest improvement in arterial stiffness — a surrogate endpoint Limited evidence

    In the same three-year cohort of 244 postmenopausal women, 180 mcg/day MK-7 significantly reduced the stiffness index beta versus placebo, with the effect concentrated in women who started with high arterial stiffness. This is a single trial measuring a surrogate, and the calcification trial above failed to corroborate the underlying story.

Dosage & safety

Studied doseTrials used 180 mcg/day of MK-7 for bone and arterial stiffness over three years, and 360-720 mcg/day in vascular calcification trials. MK-7 has a serum half-life of roughly three days versus hours for K1 and MK-4, so once-daily dosing is adequate. Do not confuse it with MK-4: the Japanese osteoporosis trials used menatetrenone at 45 mg/day, a 250-fold higher, prescription-only dose that is not interchangeable with MK-7.
SafetyWell tolerated at 180-720 mcg/day in trials lasting up to three years, with no toxicity signal and no established upper limit. The warfarin caveat applies more forcefully than for K1: MK-7's long half-life makes INR harder to re-stabilise after a change, so treat it as effectively contraindicated on warfarin, acenocoumarol or phenprocoumon unless a clinician is actively managing the dose. No interaction with DOACs. Check that a product specifies all-trans MK-7 — cis isomers are biologically inactive, and cheap synthetic products can contain a large inactive fraction with no way for the buyer to tell.

How to take it

TimingOnce a day, timing does not matter — the three-day half-life means blood levels stay steady.
With food?With a meal containing fat.
Worth knowingCheck the label says all-trans MK-7 and do not confuse it with MK-4, which was dosed at 45 mg/day in the Japanese trials — 250 times higher and not interchangeable.

Interactions

With medications

  • warfarin, acenocoumarol and phenprocoumon

    MK-7's roughly three-day half-life makes INR much harder to re-stabilise than with K1, so a change takes weeks to settle. treat as effectively off-limits on vitamin K antagonists unless a clinician is actively managing your dose

  • orlistat and bile acid sequestrants

    Fat malabsorption reduces absorption. separate by at least 4 hours

With other supplements

  • high-dose vitamin E

    High-dose vitamin E antagonises vitamin K-dependent clotting factors. do not combine megadoses

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does vitamin K2 work to prevent arterial calcification?

The evidence is limited, and the trial built to test it was negative. In AVADEC, 720 mcg/day of vitamin K2 (MK-7) for two years did not slow aortic valve calcification, even though the vitamin K biomarker improved sharply.

Does vitamin K2 MK-7 help bone health?

The evidence is moderate but rests on one trial: 180 mcg/day of vitamin K2 (MK-7) for three years slowed age-related bone loss at the lumbar spine and femoral neck in 244 postmenopausal women. Fractures were not studied.

Is vitamin K2 MK-7 the same as MK-4?

No. The Japanese osteoporosis trials used MK-4 at 45 mg/day, a prescription-only dose 250 times higher than vitamin K2 MK-7 products, so the results are not interchangeable. Look for all-trans MK-7 on the label.

Is vitamin K2 safe with warfarin?

Treat vitamin K2 (MK-7) as effectively off-limits on warfarin unless a clinician is actively managing your dose. MK-7's roughly three-day half-life makes INR much harder to re-stabilise than with K1.

Scientific references

Where to buy

Doctor's Best, Natural Vitamin K2 MK-7, 100 mcg, 60 Veggie Caps

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