Vitamin K2: What It Does, MK-7 vs MK-4 & How Much (2026)
Informational summary of published research — not medical advice. If you take warfarin or another vitamin K antagonist, do not start K2 without your physician.
The short version: vitamin K2 (menaquinone) activates the proteins that route calcium into your bones and away from your arteries. For supplementing, choose MK-7 at 90–200 mcg once daily (not MK-4, which needs a pharmaceutical dose to work), look for an all-trans label, and take it with a fatty meal. It's very safe — no established upper limit — with one big exception: if you take warfarin, don't start it without your doctor. The bone evidence is modest-but-real; the "cleans your arteries" marketing runs well ahead of the trials.
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Vitamin K2 at a glance
- What it is
- Menaquinone — the K2 family of vitamin K (distinct from K1 in leafy greens)
- What it does
- Activates osteocalcin (calcium into bone) and matrix Gla protein (calcium out of arteries)
- Best form
- MK-7 (long half-life; works at mcg doses)
- Typical dose
- 90–200 mcg MK-7 once daily
- Cost per day
- ~$0.07–0.22 for an all-trans MK-7 at 100 mcg
- With vitamin D?
- Sensible pairing, but the "45 mcg per 1,000 IU" ratio is convention, not proven
- Food sources
- Natto (by far the richest), some cheeses, egg yolk, dark chicken meat
- Upper limit
- None established; very low toxicity
- Critical caution
- Interacts with warfarin — do not start without your physician
What is vitamin K2?
Vitamin K comes in two families. K1 (phylloquinone) is the one in leafy greens, and your liver uses most of it for blood clotting. K2 (menaquinone) is a family of related forms — the two that matter for supplements are MK-7 and MK-4 — and it's the form that acts out in your bones and blood vessels. K2 is rare in the Western diet; the richest source by far is natto, a fermented soybean dish, which is why K2 status is much higher in populations that eat it.
What does vitamin K2 do?
K2 is the cofactor that switches on two calcium-handling proteins. Osteocalcin binds calcium into the bone matrix; matrix Gla protein (MGP) inhibits calcium from depositing in artery walls. Without enough K2, both stay in their inactive form. The clearest proof is dramatic: mice bred to lack MGP die within two months from their arteries calcifying. So the mental model is "rebar" — K2 helps direct calcium into the structure of bone and away from the plumbing of your arteries. The mechanism, in depth →
MK-7 vs MK-4: which form?
MK-7, for everyday use. Its long half-life (about three days) means a single 90–200 mcg dose reaches and maintains useful blood levels. MK-4 clears within hours and barely registers at supplement doses — the Japanese bone studies that used it needed a pharmaceutical 45 mg a day (taken as 15 mg three times daily), roughly 250 times a normal MK-7 dose. Unless a doctor is running that high-dose protocol, the standalone products worth buying are MK-7. Full MK-7 vs MK-4 comparison →
How much — and how much with vitamin D?
A trial-anchored MK-7 dose is 90–200 mcg per day; the 3-year bone and arterial studies used 180 mcg. There's no established upper limit — vitamin K has very low toxicity. The one number to treat skeptically is the ubiquitous "45 mcg of K2 per 1,000 IU of vitamin D" ratio: it's a formulation convention, not a validated dose (different sources quote different versions, and no trial has tested a specific ratio). The pairing logic is reasonable — D raises calcium absorption, K2 helps place it — but a standalone 90–200 mcg MK-7 is well supported whether or not it's matched to your D3. More on taking vitamin D with K2 →
What to buy — and what it costs
The good news: an effective K2 supplement is cheap. An all-trans MK-7 at 100 mcg — the trial-grade form and dose — runs about $0.07–$0.22 a day. The only real quality "tax" is making sure it's all-trans (a branded ingredient like MenaQ7) rather than a cheap synthetic that may contain the inactive cis form. Skip the MK-4-only products and anything promising to "clean" your arteries.
| Item | Value ( mcg) |
|---|---|
| MK-7 (effective dose) | 180 mcg |
| MK-4 (trial dose) | 45,000 mcg |
Our picks
Branded MenaQ7 — the all-trans, soy-free ingredient used in the clinical trials, at the standard 100 mcg dose.
The same 100 mcg MK-7 dose at the lowest cost per day — a full year in one bottle.
5,000 IU vegan D3 + 100 mcg MK-7 in one softgel, if you want the pairing in a single pill.
As an Amazon Associate we earn from qualifying purchases. Picks are ranked by form quality and cost per day, never commissions. Compare every option on the best vitamin K2 ranking.
Does it actually work?
Here's the honest picture. For bone, the case is modest but real: K2 reliably improves vitamin-K biomarkers, and one well-run 3-year trial of 180 mcg MK-7 slowed bone-density loss in postmenopausal women — though it doesn't reverse osteoporosis or replace established treatments. For arteries, the mechanism is compelling and the epidemiology is encouraging, but be careful: while K2 improves the biomarkers and modestly improved arterial stiffness in one trial, every recent adequately-powered trial that measured actual calcification — in aortic valves, diabetic arteries, and dialysis patients — came back negative. So K2 supports the system that keeps calcium out of arteries; it does not "clean out" calcium already there.
Food sources
K2 is hard to get from a typical diet. The standout source is natto (fermented soybeans), which is in a different league from everything else. After that come some fermented and aged cheeses (Gouda, Edam, Brie), egg yolk, dark chicken meat, and butter from grass-fed cows. If you don't eat natto — most people outside Japan don't — a supplement is the practical way to get a meaningful MK-7 dose.
Is it safe?
K2 has very low toxicity and no established upper limit, and no adverse effects have been reported at normal intakes. The one interaction that genuinely matters is with warfarin and other vitamin K antagonists: vitamin K opposes these drugs, and even small, inconsistent changes in intake can destabilize them — so anyone on warfarin should not start, stop, or change K2 without their physician and INR monitoring. Newer direct oral anticoagulants (apixaban, rivaroxaban, etc.) don't work through vitamin K, so this interaction isn't expected — but tell your doctor regardless.
How to choose a good one
Two things separate a good K2 supplement from a gamble. First, all-trans MK-7: only the all-trans form is biologically active, and cheap synthetic MK-7 can be contaminated with the inactive cis form — a label that says "all-trans" or names a branded ingredient (like MenaQ7) is your quality signal. Second, soy-free sourcing if you're allergic, since natto-derived MK-7 can carry trace soy (chickpea-fermented options avoid it). Aim for a dose in the studied 90–200 mcg range. See our verified MK-7 picks →
Common myths
- "K2 cleans out or reverses arterial plaque." No — the trials that tested this were negative. K2 supports calcium routing; it doesn't dissolve existing calcification.
- "MK-4 and MK-7 are interchangeable." They're not — MK-4 needs a milligram pharmaceutical dose to do what MK-7 does at micrograms.
- "You must match K2 to your vitamin D at 45 mcg per 1,000 IU." That ratio is convention, not evidence. A standalone 90–200 mcg MK-7 is fine.
- "More K2 is stronger." Benefits track the studied 90–200 mcg range; megadosing hasn't been shown to add anything.
The full guides
MK-7 vs MK-4 (Forms & Dosage)
Why the form decides the dose, how much to take with vitamin D, the all-trans quality issue, the warfarin caution, and an honest look at whether K2 does anything for arteries.
Best Vitamin K2 Supplement
Verified MK-7 picks ranked by form quality, all-trans content, and cost per day — plus the best D3+K2 combo and what to avoid.
Frequently Asked Questions
What does vitamin K2 do?
Vitamin K2 activates two proteins that manage calcium: osteocalcin, which binds calcium into bone, and matrix Gla protein, which helps keep calcium out of artery walls. In plain terms, K2 helps route calcium toward your skeleton and away from your arteries. The bone evidence is modest but real; the artery benefit is mechanistically compelling but has not held up in recent hard-outcome trials.
Should I take MK-7 or MK-4?
MK-7, for everyday supplementation. It has a long half-life (about three days), so 90–200 mcg once daily reaches and holds useful blood levels. MK-4 is cleared within hours and is barely detectable at supplement doses — the bone studies that used it needed a pharmaceutical 45 mg a day (taken as 15 mg three times daily), about 250 times a typical MK-7 dose. Choose MK-7 unless a doctor is specifically running the high-dose MK-4 protocol.
How much vitamin K2 should I take with vitamin D?
A reasonable, trial-anchored MK-7 dose is 90–200 mcg per day; the 3-year studies used 180 mcg. The popular "45 mcg of K2 per 1,000 IU of vitamin D" ratio is a formulation convention, not a validated number — no dose-ranging trial has tested a specific D-to-K2 ratio. Take K2 with a fatty meal. If you take warfarin or another vitamin K antagonist, do not start K2 without your physician.
Is vitamin K2 safe with blood thinners?
Not without medical oversight if the blood thinner is a vitamin K antagonist such as warfarin. Vitamin K opposes warfarin, and MK-7 at supplement doses (50 mcg or more) can interfere with it — consistency of intake matters. Newer direct oral anticoagulants (apixaban, rivaroxaban, dabigatran, edoxaban) do not work through vitamin K, so this interaction is not expected, but tell your physician either way.
Does vitamin K2 have side effects?
Vitamin K2 is very well tolerated — it has no established upper limit and no adverse effects have been reported at normal supplement doses. The one thing that matters is not a side effect but an interaction: K2 opposes warfarin and other vitamin K antagonists, so anyone on those medications should not start K2 without their doctor and INR monitoring.
When is the best time to take vitamin K2?
Take it with a meal that contains some fat, since K2 is fat-soluble. Beyond that, timing barely matters: MK-7 has a roughly three-day half-life, so morning versus night makes little difference — taking it consistently at the same time each day is more useful than any specific hour.
About our data
Every guide draws on clinical evidence from PubMed systematic reviews and randomized trials (each citation verified against the primary source), with product picks ranked by form quality and cost per day. See our methodology and editorial standards.