MK-7 is a specific form of vitamin K2, a fat-soluble nutrient that helps your body direct calcium to the right places: into bones and teeth, and away from arteries and soft tissues. Its full chemical name is menaquinone-7, and it stands out from other forms of vitamin K because it stays active in your bloodstream far longer, accumulating to levels seven to eight times higher than vitamin K1 during regular supplementation.
How MK-7 Fits Into the Vitamin K Family
Vitamin K comes in two main forms. Vitamin K1 (phylloquinone) is found in green leafy vegetables and is the most common form in the diet. Vitamin K2 is actually a group of related compounds called menaquinones, each named for the length of its chemical side chain. MK-4 has four repeating units, MK-7 has seven, and so on up to MK-13. The “MK” stands for menaquinone, and the number tells you how long the molecule’s tail is.
That tail length matters. MK-4, the short-chain version often used in older supplements, is barely detectable in the blood after a single dose. In a direct comparison, when healthy women took 420 micrograms of either MK-4 or MK-7, MK-4 never showed up in their serum at any time point. MK-7 peaked at six hours and remained detectable for up to 48 hours. This long half-life is the core advantage of MK-7: it circulates long enough to reach tissues throughout the body and keep working there.
What MK-7 Does in Your Body
MK-7 serves as a helper molecule (a cofactor) for a specific chemical reaction called carboxylation. Think of it as flipping a switch on certain proteins so they can do their jobs. Two of the most important proteins MK-7 activates are osteocalcin and matrix Gla protein.
Osteocalcin, once activated, binds calcium and drives it into bone tissue. Without enough vitamin K2 to switch it on, osteocalcin floats around in an inactive form, and bones miss out on calcium they need for strength. Matrix Gla protein works on the other side of the equation: once activated by vitamin K2, it prevents calcium from depositing in artery walls and other soft tissues. It does this by binding free calcium in cells and by blocking signals that would otherwise cause blood vessel cells to transform into bone-like cells. In short, MK-7 helps calcium go where it’s needed and stay away from where it causes damage.
Bone Health Effects
A three-year randomized, placebo-controlled trial in postmenopausal women with early bone loss found that 375 micrograms of MK-7 daily, added to calcium and vitamin D, significantly increased the activation of osteocalcin. Activated osteocalcin is the form that actually promotes bone mineralization, so this finding connects directly to stronger bone tissue. The trial specifically measured the carboxylation (activation) rate of osteocalcin as its primary marker of whether the supplement was working, and MK-7 clearly improved it compared to placebo.
Cardiovascular Effects
Arterial calcification, the buildup of calcium in blood vessel walls, is a major contributor to stiffness and cardiovascular disease. MK-7 counteracts this through matrix Gla protein activation. In a double-blind clinical trial, 180 micrograms of MK-7 taken daily for three years improved markers of cardiovascular health in a healthy population. A separate one-year trial in 243 people aged 40 to 70 who were at elevated cardiovascular risk due to vitamin K insufficiency found that the same 180-microgram daily dose significantly decreased both inactive matrix Gla protein levels and arterial stiffness, measured by pulse-wave velocity. Arterial stiffness is one of the strongest predictors of cardiovascular events, so reducing it is a meaningful outcome.
Best Food Sources of MK-7
Natto, a traditional Japanese dish made from fermented soybeans, is by far the richest food source. Standard natto contains roughly 775 micrograms of MK-7 per 100 grams, and fortified versions can reach 1,300 to 1,765 micrograms per 100 grams. Studies in Japanese populations have shown that regular natto consumption measurably raises both circulating MK-7 and activated osteocalcin levels.
Certain aged and fermented cheeses contain MK-7 as well, though at much lower concentrations. Münster cheese made from raw milk leads the list at about 84 nanograms per gram, followed by Camembert at 32, Gorgonzola at 31, and Cheddar at 19. Dutch cheeses like Gouda range from about 14 to 17 nanograms per gram. To put this in perspective, you would need to eat several hundred grams of Münster cheese to match the MK-7 in a small serving of natto. For people who don’t eat natto regularly, supplements are the most practical way to get meaningful amounts.
How MK-7 Supplements Are Made
Most MK-7 supplements are produced through bacterial fermentation, using the same species of bacteria (Bacillus subtilis) that creates natto. In commercial production, the bacteria ferment soybean-based or other growth media, and the MK-7 is extracted and purified. This process yields a natural, long-chain form of the vitamin identical to what you’d find in fermented foods. Some supplement labels specify the fermentation source, which can be useful if you have soy allergies and need a soy-free version.
Absorption and How to Take It
MK-7 is fat-soluble, so it needs dietary fat to be absorbed properly. Your body takes it up in the small intestine, where it gets incorporated into fat-carrying particles for transport through the bloodstream. In absorption studies, participants took their MK-7 dose within 10 minutes of a breakfast containing 13 to 17 grams of fat. Taking it with a fat-free meal or on an empty stomach will reduce how much you absorb.
The delivery format also makes a difference. Oil-based softgel capsules release MK-7 faster than dry powder tablets, with capsules reaching peak blood levels in two to four hours compared to six hours for tablets. If you’re choosing between formats, softgels paired with a meal containing some fat will give you the best absorption.
Typical Supplement Doses
The most commonly studied dose in clinical trials is 180 micrograms per day, which is the amount that produced measurable cardiovascular benefits over one to three years. Some bone health trials have used 375 micrograms per day. Most over-the-counter supplements fall in the 100 to 200 microgram range. There is no established upper limit for MK-7, and the doses used in clinical research have not shown toxicity in healthy adults.
Interaction With Blood Thinners
If you take warfarin or a similar anticoagulant, MK-7 supplements deserve serious caution. Warfarin works by blocking the same enzyme that vitamin K2 uses to activate clotting factors. Adding MK-7 can counteract warfarin’s effect, pushing your clotting ability back toward normal in a dose-dependent way. In clinical settings, vitamin K2 is actually used intentionally to reverse warfarin’s effects when bleeding becomes dangerous. Even supplemental doses of MK-7 could shift your INR (the measure of how thin your blood is) enough to reduce warfarin’s protective effect. Anyone on warfarin or similar medications should talk to their prescribing doctor before adding MK-7 to their routine.