MK-7 vs MK-4 (2026): Which Vitamin K2 & How Much to Take?

By Erin Rose · Published July 11, 2026 · Updated July 11, 2026 · Methodology

Also searched: menaquinone-7 vs menaquinone-4, MK7 vs MK4, natto K2 vs synthetic.

Informational summary of published research — not medical advice. If you take warfarin or another vitamin K antagonist, do not start K2 without your physician.

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Why the form decides the dose

MK-7 and MK-4 are both vitamin K2, but they behave completely differently in the body — and that single fact explains every dosing recommendation on this page. In a head-to-head bioavailability study, MK-7 was well absorbed and still measurable 48 hours after a single dose, while MK-4 was not detectable in the blood of any subject at nutritional doses. MK-7's long half-life lets it accumulate to 7–8× higher serum levels than other forms on daily dosing.

MK-4 isn't useless — Japan approves a 45 mg/day menatetrenone drug for osteoporosis, and pooled trials showed a fracture benefit at that dose. But 45 mg a day is 45,000 mcg, taken as 15 mg three times daily to work around the short half-life — roughly 250 times a standard MK-7 supplement. That's a pharmaceutical regimen, not what's in a 100 mcg capsule. For supplementation, MK-7 is simply the practical choice.

What about MK-4 for bone density?

One honest counterpoint: the strongest fracture evidence actually comes from MK-4, not MK-7. A meta-analysis of the Japanese trials found high-dose MK-4 (the 45 mg-a-day menatetrenone drug) was associated with fewer vertebral and hip fractures. So why still recommend MK-7? Two reasons: those trials used a pharmaceutical 45 mg dose, not the microgram amount in a supplement, and many were small, older, and open-label — and a later, larger trial of high-dose vitamin K (as K1) was negative for bone density. MK-7's cleaner evidence is a 3-year, 180 mcg RCT that slowed bone loss at a practical dose. Bottom line: the specific MK-4 osteoporosis protocol is a 45 mg-a-day conversation with your doctor — for everyday bone and vascular support, 90–200 mcg of MK-7 is the sensible choice.

How much K2 — and how much with vitamin D?

A sensible, trial-anchored MK-7 dose is 90–200 mcg per day. The 3-year studies that showed benefits for bone and arterial stiffness used 180 mcg/day. There's no established upper limit — the Food and Nutrition Board set no tolerable upper intake level for vitamin K because of its low toxicity.

The one number you'll see everywhere — "45 mcg of K2 per 1,000 IU of vitamin D" — deserves an honest caveat: it's a formulation convention, not a clinically validated ratio. Different sources quote different versions (10, 20, 45, even 100 mcg per 1,000 IU), and no dose-ranging trial has ever tested a specific D-to-K ratio. The mechanistic logic is sound (vitamin D raises calcium absorption; K2 helps route that calcium into bone), but the exact pairing number is convenience, not evidence. Practically: a standalone 90–200 mcg MK-7 is well supported whether or not it's matched to your D3 dose. Food is rarely enough — natto (fermented soybeans) is by far the richest source, with much smaller amounts in aged cheese and egg yolk — which is why most people who want a meaningful dose supplement it.

The "rebar" mechanism — what K2 actually does

Vitamin K2 is the cofactor that activates two calcium-handling proteins: osteocalcin, which binds calcium into bone, and matrix Gla protein (MGP), which stops calcium depositing in artery walls. Without enough K2, these proteins stay in their inactive form — measured in the blood as undercarboxylated osteocalcin (ucOC) and dephospho-uncarboxylated MGP (dp-ucMGP), the same markers that improved in the trials discussed below. Mice engineered to lack MGP die within two months from arterial calcification — the clearest proof that this protein, and the vitamin K that switches it on, keeps calcium where it belongs. Think of K2 as the crew that directs calcium into the "rebar" of bone and away from the plumbing of your arteries.

Does K2 "clean out" arteries? The honest answer

This is where marketing outruns the evidence, so here's the careful version. K2 reliably improves the biomarkers of vitamin K status, and in one well-run 3-year trial in healthy postmenopausal women, 180 mcg/day MK-7 modestly improved arterial stiffness. The observational Rotterdam Study also linked higher dietary K2 to less heart disease.

But every recent, adequately powered trial that measured actual calcification came back negative: an aortic-valve trial (720 mcg MK-7 + D, 2 years), a diabetic-artery trial, and a dialysis trial all found no benefit on their primary calcification endpoint. So the defensible claim is: K2 supports the system that keeps calcium out of arteries and may help maintain arterial flexibility — but it does not "clean out," dissolve, or reverse calcium that's already there.

The quality issue: all-trans vs cis MK-7

MK-7 comes in two shapes. Only the all-trans form is biologically active; the cis form — a byproduct of poorly controlled synthesis — is markedly less able to activate vitamin-K proteins. Fermentation-derived and branded MK-7 ingredients (like MenaQ7, the ingredient used in most of the clinical trials) are tested to guarantee all-trans content; cheap generic synthetic MK-7 can carry inactive cis contamination. Two things to check on a label: "all-trans" or a named ingredient brand, and — if you're allergic — whether the MK-7 is soy-free (natto is fermented soy; chickpea-fermented options exist).

Safety & the warfarin interaction

• Warfarin / vitamin K antagonists (the critical one): vitamin K opposes warfarin. MK-7 at supplement doses (50 mcg or more) can interfere with anticoagulation, and even small, inconsistent changes in vitamin K intake have destabilized patients. If you take warfarin or acenocoumarol, don't start, stop, or change K2 without your physician and INR monitoring.
• Newer blood thinners (DOACs): apixaban, rivaroxaban, dabigatran, and edoxaban don't work through vitamin K, so this interaction isn't expected — but tell your doctor anyway.
• No upper limit: vitamin K has no established toxic dose, and no adverse effects have been reported from food or supplements at normal intakes.
• With food: K2 is fat-soluble — take it with a meal containing some fat, at a consistent time. Its long half-life means morning vs night doesn't matter.

Frequently Asked Questions

Related Guides

• Best Vitamin K2 Supplements — Verified MK-7 and D3+K2 picks, ranked
• All Vitamin K2 Guides
• Vitamin D with K2 — How the pairing works and whether you need it
• Vitamin D Dosage Guide — How much D3, and where K2 fits
• Calcium for Bones — The other half of the bone equation

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