Pepdexpepdex
Stack
← All supplements

Vitamin K2

Menaquinone / MK-7 / MK-4 · Foundation

LimitedLittle human data, early, small, or narrow.

Directs calcium toward bone and away from arteries in theory; the human outcome data is thinner than the pairing with D3 implies.

250-fold
Nominal daily mass gap between the 45 mg MK-4 bone trials and a typical 180 mcg MK-7 supplement (different vitamers, not a potency equivalence)

What it is

The vitamin that tells calcium where to go, into bone rather than arteries. It is the quiet counterpart to vitamin D, and the reason "D3+K2" became a standard pairing, though the pairing rests more on mechanism than on outcome trials.

How it works

K2 activates two proteins: osteocalcin, which binds calcium into bone, and matrix Gla protein, which stops calcium depositing in artery walls. Vitamin D increases calcium absorption; K2 is proposed to direct where it lands. Elegant, plausible, and only partly tested in humans.

Which form to buy

MK-7 (menaquinone-7)Daily supplementation

Long half-life means once-daily dosing holds levels; the form in most modern trials, typically 90-180 mcg.

The practical default.

MK-4 (menaquinone-4)The Japanese trial base

Short half-life; the osteoporosis trials used a pharmacological 45 mg PER DAY total (typically 15 mg three times daily), not what supplements provide.

Do not assume supplement doses replicate those trials.

K1 (phylloquinone)Clotting, from greens

The leafy-green form, mostly used by the liver for clotting factors.

Different job; a normal diet covers it.

NattoThe food source

Fermented soybeans, by far the richest MK-7 source, and an acquired taste.

The original, if you can stomach it.

What it actually does, graded

Improves bone mineral density markersLimited

Mixed: some trials show benefit, others none, and the strongest osteoporosis data used pharmacological MK-4 doses far above supplements.

Reduces arterial calcification progressionLimited

Mixed: dialysis trials improved inactive-MGP markers WITHOUT slowing calcification, and postmenopausal work measured arterial stiffness instead. A 2026 RCT did find modestly slowed coronary calcium progression at 360 mcg MK-7 in symptomatic coronary disease, clinical significance unknown.

Reduces fracture riskLimited

Not consistently demonstrated in Western populations at supplement doses.

Required alongside vitamin D to prevent harmNone shown

A very common marketing claim. No trial shows vitamin D supplementation causes arterial calcification that K2 then prevents.

Pros and cons

Pros
  • A genuinely elegant mechanism with real biology behind it
  • Safe at supplement doses with a long usage history
  • Cheap when bought as MK-7
Cons
  • The D3+K2 pairing is sold as necessary; the evidence for necessity is not there
  • The impressive bone trials used doses 250x higher than typical supplements
  • A genuine, serious interaction with warfarin

What to expect

  • Nothing perceptible, the studied outcomes are bone density and arterial scans over years.

Interactions

AvoidWarfarin and other vitamin-K antagonistsVitamin K directly opposes how these drugs work. This is the interaction that actually matters, consistency of intake is what anticoagulation clinics manage, and adding a supplement without telling them is genuinely risky.
CompatibleVitamin DThe intended pairing, though "necessary" overstates the evidence.

Is it for you?

Probably worth it if
  • You already supplement vitamin D and want the mechanistically sensible companion, with expectations set low
  • Bone-density concerns you are managing with a clinician
Probably skip it if
  • You eat plenty of greens and fermented foods and take no vitamin D

Who should avoid it

  • Anyone on warfarin or another vitamin-K antagonist, without their anticoagulation clinic explicitly agreeing

Research on this supplement

Papers about this supplement, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

  • The effect of vitamin K2 supplementation on bone turnover biochemical markers in postmenopausal osteoporosis patients: a systematic review and meta-analysis
    Front Endocrinol (Lausanne), 2025
  • The effect of vitamin K supplementation on cardiovascular risk factors: a systematic review and meta-analysis
    J Nutr Sci, 2024
  • Efficacy of vitamin K2 in the prevention and treatment of postmenopausal osteoporosis: A systematic review and meta-analysis of randomized controlled trials
    Front Public Health, 2022

What the evidence says

The mechanism is real. K2 activates proteins that regulate where calcium is deposited. Human outcome evidence is where it thins: a few bone-density and arterial-stiffness trials with modest or mixed results, and nothing establishing that adding K2 to D3 changes fracture or cardiovascular outcomes. The routine D3+K2 pairing is mechanistic reasoning sold as an established requirement.

What studies used

MK-7 trials commonly used 90-180 mcg/day. Fat-soluble; studies dosed it with meals.

Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.

Watch out for

  • Vitamin K directly opposes warfarin, anyone anticoagulated needs their prescriber involved before starting or stopping it, and consistency matters more than amount

Evidence base

A8,926 research papers
established literature

Strong human evidence: either a phase 3 or 4 trial report alongside review-level evidence, or ten or more randomised controlled trial reports.

This letter measures how much human research exists, not whether it works for you — the tier above (Limited) is the read on quality.

Research (12)

Turn Vitamin K2 into a plan that's yours

The info above is free. Membership makes it personal, the Coach answers questions about your exact stack, the Stack tracks it for you, and the Verified Sources shows you how to vet what you buy.

  • ✓ AI Coach, ask anything about your stack. It does the dosing math, flags interactions, and tells you what to do next.
  • ✓ Personal Stack, save your protocol, track it across devices, log doses, get a heads-up before a vial runs out.
  • ✓ Verified Sources, the vetted reference for checking quality and sourcing, members only.
Become a member, from $4.99/week

Cancel anytime · or save with $59.99/yr · Coach + Stack included

Where next

Every supplement in the catalogThe full shelf, grouped and evidence-tiered.→The compound indexSteroids, nootropics and research chemicals.→The peptide indexInjectable peptides and what trials used.→