Can I Take Vitamin K2 With Nattokinase?

Taking vitamin K2 alongside nattokinase is safe for most people, and the two substances naturally coexist in the same food. Natto, the traditional Japanese fermented soybean dish, is the richest dietary source of a specific form of vitamin K2 called MK-7 and is also the original source of the enzyme nattokinase. The combination raises legitimate questions, though, because vitamin K2 supports blood clotting pathways while nattokinase works against clot formation, and understanding how those actions interact matters before you start supplementing with both.

The Natto Connection

The reason vitamin K2 and nattokinase come up together so often is that they literally come from the same place. Natto is produced by fermenting soybeans with the bacterium Bacillus subtilis, and during that fermentation process, the bacteria generate both nattokinase (a fibrin-dissolving enzyme) and large quantities of menaquinone-7, the long-chain form of vitamin K2. A single 50-gram serving of natto provides roughly 380 micrograms of MK-7, which is far more than most K2 supplements contain per capsule.¹ People in Japan who eat natto regularly have been consuming both compounds together for centuries without any documented pattern of harm from the combination itself. The concern that one might cancel out or interfere with the other does not hold up when you look at what each substance actually does in the body.

How They Work Differently in the Body

Vitamin K2 and nattokinase act through entirely separate biological pathways, which is a big part of why they do not clash when taken together.

Vitamin K2 serves as a cofactor for an enzyme that activates certain proteins by attaching a chemical group to them. Two of the most important are matrix Gla protein (MGP), which helps keep calcium from depositing in artery walls, and osteocalcin, which directs calcium into bones. Without enough vitamin K2, these proteins sit around in their inactive forms, unable to do their jobs. The cardiovascular angle is straightforward: activated MGP helps prevent arterial stiffening, while activated osteocalcin promotes bone mineralization.² Vitamin K2 also plays a role in activating clotting factors, though this is primarily the domain of vitamin K1, which the liver preferentially uses for coagulation.

Nattokinase is a serine protease, meaning it cuts apart other proteins. Its main target is fibrin, the mesh-like protein that forms the structural backbone of blood clots. In lab studies, nattokinase not only cleaves fibrin directly but also boosts the body’s own clot-dissolving system by increasing tissue-type plasminogen activator activity and reducing the levels of its main inhibitor.³ So nattokinase works on the clot-dissolving side of the equation, while vitamin K2 works on calcium-protein activation. They are not pulling in opposite directions so much as working in different rooms of the same house.

Why People Stack Them Together

The appeal of combining vitamin K2 and nattokinase comes down to cardiovascular health, though from two distinct angles. Vitamin K2’s activation of MGP helps prevent the buildup of calcium in blood vessel walls, a process called vascular calcification that is a major contributor to arterial stiffness and heart disease risk. Nattokinase, meanwhile, supports healthy blood flow by breaking down excess fibrin and potentially lowering blood pressure. One review paper examining both substances noted that vitamin K has been associated with reduced risk of cardiovascular disease through improved vascular elasticity, while nattokinase contributes through its fibrinolytic (clot-dissolving) activity.⁴

People interested in bone health also have reason to take both. Vitamin K2 activates osteocalcin, which promotes bone mineralization and helps maintain bone density. A meta-analysis of Japanese studies found that habitual natto consumption was associated with increased carboxylated osteocalcin, decreased undercarboxylated osteocalcin (the inactive form), and modestly greater bone mineral density.¹ Nattokinase itself does not directly build bone, but its cardiovascular support may contribute to overall health in populations that are also at risk for osteoporosis, particularly postmenopausal women. Taking them together is less about synergy between the two molecules and more about efficiently covering two related health goals with one supplement stack.

Which Form of Vitamin K2 Pairs Best

If you are pairing vitamin K2 with nattokinase, the form of K2 you choose matters more than you might think. The two most common supplemental forms are MK-4 and MK-7, and they behave quite differently once you swallow them.

MK-4 has a short half-life in the blood. After a single dose, serum levels rise briefly and then drop off quickly. MK-7, on the other hand, sticks around much longer, building up to stable blood levels with regular daily dosing. A study comparing the bioavailability of different vitamin K forms found that longer-chain menaquinones like MK-7 had much larger areas under the curve and longer half-lives compared to MK-4, meaning more of the vitamin reaches your tissues over a longer window.⁵ This is why most supplement manufacturers pair nattokinase with MK-7 rather than MK-4: MK-7 is the form naturally produced during natto fermentation, and its longer duration of action means a once-daily dose can sustain meaningful blood levels throughout the day.

MK-4 is not useless, but it typically requires much higher doses (often in the milligram range rather than microgram range) to achieve therapeutic tissue concentrations, and it needs to be taken multiple times per day. If convenience and steady-state blood levels are your priority, MK-7 is the more practical partner for nattokinase in a daily supplement routine. Many combination products on the market already reflect this, packaging MK-7 and nattokinase together in a single capsule.

When the Combination Gets Risky

For healthy people not on blood-thinning medications, the vitamin K2 and nattokinase combination does not raise red flags. The risk picture changes substantially, however, if you are taking anticoagulants or antiplatelet drugs.

Vitamin K2, like all forms of vitamin K, can interfere with warfarin (Coumadin). Warfarin works by blocking the vitamin K cycle, preventing the activation of clotting factors. When you add vitamin K2 to the mix, you are essentially working against the drug’s mechanism. This does not mean vitamin K2 is dangerous on its own, but for someone whose dose of warfarin has been carefully calibrated, even modest changes in vitamin K intake can throw off their INR (a measure of how quickly blood clots). If you are on warfarin, any change in vitamin K2 intake needs to be discussed with whoever manages your anticoagulation therapy.

Nattokinase adds its own layer of concern for people on blood thinners. Because it dissolves fibrin and enhances the body’s clot-busting pathways, stacking it with an anticoagulant or antiplatelet drug could increase bleeding risk. One case report described a cerebellar hemorrhage in a patient who was taking nattokinase alongside aspirin and who had underlying cerebral microbleeds. The authors suggested that nattokinase may raise the risk of intracerebral hemorrhage in people with bleeding-prone small vessel disease who are already on an antithrombotic agent.⁶ A broader review of supplements with anti-atherosclerotic effects, including nattokinase, noted that clinical usefulness depends on formulation, dosage, and patient characteristics, and may be limited by bleeding risk or drug interactions.⁷

The bottom line for people on medication: combining vitamin K2 and nattokinase with each other is not the problem. Combining either of them with prescription blood thinners is where real trouble can start. Vitamin K2 counteracts warfarin’s effect, and nattokinase amplifies anticoagulant and antiplatelet effects. If you are on any blood-thinning drug, do not add either supplement without medical guidance.

Nattokinase and Blood Pressure

Beyond its better-known clot-dissolving role, nattokinase appears to have a separate effect on blood pressure that makes the combination with K2 even more appealing for cardiovascular-minded supplement users. When nattokinase is digested, it releases small peptides that inhibit angiotensin-converting enzyme (ACE), the same target that prescription ACE inhibitor drugs go after. Researchers have identified specific peptides released during digestion of nattokinase that show potent ACE-inhibitory activity in laboratory testing.⁸

This means nattokinase may offer mild blood pressure support on top of its fibrinolytic effects, though it is worth noting that lab-demonstrated ACE inhibition and real-world blood pressure reduction in humans are not always the same thing. Several small clinical trials have shown modest blood pressure drops with nattokinase supplementation, but the evidence is not yet strong enough to call nattokinase a reliable antihypertensive. Still, for someone already taking it alongside vitamin K2 for cardiovascular reasons, the potential blood pressure benefit is a reasonable bonus rather than a reason to add a new supplement.

If you are already on ACE inhibitors or other blood pressure medications, the same caution applies here as with blood thinners: adding nattokinase could amplify the drug’s effect and drop your blood pressure more than expected. This is worth mentioning to your doctor, even though nattokinase is a food-derived supplement and not a prescription drug.

What Natto Eaters Can Teach Us About Long-Term Safety

One of the strongest pieces of indirect evidence that vitamin K2 and nattokinase are safe together comes from epidemiological data on Japanese natto consumption. People who eat natto regularly are getting both compounds in significant quantities with every serving. The meta-analysis of Japanese studies on habitual natto intake found that regular consumption was associated with significantly elevated serum MK-7 levels and improved markers of vitamin K status, including better osteocalcin activation and modestly higher bone mineral density, without reports of adverse interactions between the K2 and nattokinase components of the food.¹

This does not guarantee that high-dose supplements behave identically to whole-food natto. Supplements can deliver concentrated forms of both compounds at doses that exceed what a normal diet provides, and the absorption dynamics of a capsule differ from those of a fermented food eaten with a meal. But the centuries-long track record of natto consumption offers meaningful reassurance that these two compounds do not create problems when they coexist in the body. The safety question is less about whether K2 and nattokinase interact with each other and more about whether either one interacts with something else you are taking.

Timing and Practical Considerations

Vitamin K2, particularly MK-7, is fat-soluble. Your body absorbs it much more effectively when you take it with a meal that contains some dietary fat. If your nattokinase supplement is in the same capsule as your K2, taking it with dinner or another fat-containing meal makes sense. If they are in separate capsules, there is no requirement that they be taken at the same time, but taking K2 with food is worth prioritizing.

Nattokinase is often taken on an empty stomach under the theory that it will reach the bloodstream faster without competition from food proteins. Some people split the difference by taking nattokinase in the morning before breakfast and K2 with a later meal. There is no clinical trial comparing these timing strategies head to head, so the practical advice boils down to: take K2 with fat, and take nattokinase whenever you will consistently remember it.

Dosing ranges for K2 in supplement form typically run from 100 to 200 micrograms of MK-7 per day, though higher doses appear in some products. Nattokinase doses are usually measured in fibrinolytic units (FU), with common products providing 2,000 FU per capsule. Neither supplement has an established upper limit set by major regulatory agencies, which is partly a reflection of the limited large-scale safety data and partly because both substances have shown a wide margin of safety in the studies that do exist.

One practical note: many nattokinase supplements derived from natto fermentation already contain some residual vitamin K2 unless the manufacturer specifically removes it. If you are trying to avoid vitamin K (for instance, because you take warfarin), look for nattokinase products explicitly labeled as “vitamin K-free” or “K2-removed.” Conversely, if you want both compounds, a product that retains the naturally occurring MK-7 saves you from buying a separate K2 supplement.

Vitamin K2 and Soft Tissue Calcification

One angle that draws people to the K2-nattokinase stack specifically is the idea that vitamin K2 can help reverse arterial calcification rather than merely slow it down. The mechanism is plausible: activated MGP is one of the body’s primary defenses against calcium being deposited where it should not be, and K2 is required to activate MGP. Observational studies have linked higher vitamin K2 intake to lower rates of vascular calcification and cardiovascular death, and the biological pathway through which K2 activates MGP and osteocalcin is well established.²

Whether supplemental K2 can actually reverse existing calcification in human arteries is less certain. A few clinical trials have tested this directly, with mixed results. Some showed slowed progression of calcification; reversal has been harder to demonstrate convincingly. The promise is real enough that research continues, but anyone hoping that K2 supplements will dissolve years of calcium buildup in their arteries should keep expectations moderate. What the evidence does support is that adequate vitamin K2 helps keep the calcium-regulating proteins active, which is a reasonable preventive measure and pairs logically with nattokinase’s role in maintaining healthy blood flow.

Adding nattokinase to the picture does not directly address calcification, since nattokinase targets fibrin rather than calcium deposits. But the two supplements address different contributors to cardiovascular aging: K2 works on the calcium side, nattokinase works on the clotting side, and together they cover more ground than either one alone. This is probably the most honest way to think about the combination, as complementary rather than synergistic, with each doing its own job independently.