Vitamin K2 (MK-7)

vitamin K2 · menaquinone · MK-7 · MK-4

A vitamin promoted for directing calcium to bones and away from arteries.

TypeSupplement / dietary

The grade answers: What does the human evidence support for: Bone & vascular health?

Grade

Limited

The grade rates evidence quality — it is not advice to take or buy.

Class: Fat-soluble vitamin
Primary use: Bone & vascular health
Evidence strength: low
Last reviewed: 2026-07-01

Bottom line

A plausible role in bone and vascular calcium handling, with mostly surrogate-marker evidence. Interesting and safe, but hard clinical-outcome data are limited.

What the evidence says

Vitamin K2 activates proteins (osteocalcin, matrix Gla protein) that help deposit calcium in bone and inhibit its deposition in arteries — a genuinely appealing mechanism. Human trials show it improves these markers and some bone-density measures, and it's often paired with vitamin D. But evidence on hard endpoints (fractures, cardiovascular events) is limited and mixed, and much of the enthusiasm is mechanistic. Grade C: sound biology, thin outcome proof.

Key studies

[1]
Vitamin K2 and bone health · review
Improves markers/density; fracture data limited.
Open on PubMed ↗
[2]
Vitamin K2 and arterial calcification · RCT
Signals on vascular markers; outcome evidence sparse.
Open on PubMed ↗
[3]
Vitamin K-dependent proteins (review) · review
Explains the calcium-routing mechanism.
Open on PubMed ↗

See all studies on PubMed ↗

Scoped PubMed search, not a curated bibliography: the individual PMIDs for this entry have not yet been verified one by one. For that reason it is not used to support a high grade and is awaiting review.

Mechanism

Serves as a cofactor for γ-glutamyl carboxylation of vitamin-K-dependent proteins, activating osteocalcin (bone) and matrix Gla protein (vascular calcification inhibitor).

Safety

Well tolerated with a wide safety margin. Important caveat: vitamin K interacts with warfarin and similar anticoagulants — anyone on those drugs must not change vitamin K intake without medical supervision.

Dosage context

Supplements commonly provide ~90–200 µg/day of MK-7. The MK-7 form has a longer half-life than MK-4; optimal dose and long-term benefit are not settled.

Examples of application

Taken as MK-7 (~90–200 µg/day), often alongside vitamin D.
Must not be changed by anyone on warfarin without medical advice.
Judged on markers; hard-outcome evidence is still limited.

From the field

K2 has one of the more elegant mechanisms in the supplement aisle — and one of the gaps between mechanism and outcomes. We grade it C and flag the warfarin interaction, which the marketing tends to skip.

Related molecules

Vitamin DC

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