Vitamin K2 MK-7 vs MK-4: Which Form to Choose

MK-4 and MK-7 are both forms of vitamin K2, so neither is “real” K2 and the other an imitation. They differ in where they come from, how long they stay in your blood, and how much the research behind each one covers. For a daily supplement, MK-7 has the stronger case for convenience and for raising markers of vitamin K status at nutritional doses. MK-4 has a different history, with a few Japanese trials that used very large doses. Below, we explain what separates them, what the evidence does and does not show, and who should talk to a clinician first.

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TL;DR

MK-4 and MK-7 are both menaquinones, the vitamin K2 group. K1 (phylloquinone) is a separate type of vitamin K.
MK-7 stays in the blood much longer and has been studied at nutritional doses of roughly 90 to 180 micrograms a day. MK-4 is cleared quickly, and the human trials that showed bone effects used about 45 mg a day, a pharmacological dose.
Evidence for bone health is promising but limited. Evidence for heart health is inconclusive in clinical trials.
If you take warfarin or a similar anticoagulant, do not start any vitamin K supplement without your prescriber, because consistency matters.

What MK-4 and MK-7 actually are
How they differ in the body
What the research shows for bone health
What the research shows for heart health
MK-7 or MK-4: how to choose
Safety: who needs to check first
Our perspective
Build your K2 routine with Kikaboni
FAQ
Sources

What MK-4 and MK-7 actually are

Vitamin K is a family of fat-soluble compounds. According to the NIH Office of Dietary Supplements, vitamin K1 is phylloquinone, and vitamin K2 is a group of menaquinones labeled MK-4 through MK-13. So MK-4 and MK-7 are two forms of K2, not alternatives to vitamin K itself.

The number refers to the length of the side chain, counted in isoprenyl units. That chain length matters. Researchers describe it as a main driver of transport, half-life and tissue distribution for each form.

Where each form comes from

MK-4 is unusual. The NIH notes that the human body can produce it from vitamin K1. It also appears in animal foods such as eggs, butter and some meats.

MK-7 is a long-chain menaquinone made by bacteria. It is found in fermented foods, with natto, the fermented soybean dish, being the best-known source, and it is the form most often used in over-the-counter supplements. A 2021 review describes MK-4 as formed in human and animal tissue from K1, and MK-7 as produced by bacteria, including during natto fermentation.

	MK-4	MK-7
Side chain	Short (4 units)	Long (7 units)
Typical source	Animal foods; made in the body from K1	Fermented foods such as natto; supplements
Time in blood	Short	Long, detectable for days
Doses studied in humans	Often 45 mg a day in bone trials	Often 90 to 180 mcg a day
Dosing frequency in practice	Usually split through the day	Once daily

How they differ in the body

The biggest practical difference is how long each form lasts after you take it.

In a 2012 study of healthy Japanese women, serum MK-7 peaked about 6 hours after a dose and was still detectable at 48 hours. After a 420 microgram dose of MK-4, it was not detected at any measured time point. When the same researchers gave 60 micrograms a day for seven days, MK-7 levels rose in every participant, while MK-4 levels did not rise. The authors concluded that MK-7 may matter more for vitamin K status in tissues outside the liver.

Other academic work agrees on the direction. A 2021 review reports that MK-7 has a far longer plasma half-life than MK-4 or K1. Long-chain menaquinones can be detected in circulation up to 96 hours after administration, which allows more exposure for tissues outside the liver.

Two cautions keep this in perspective:

A short time in the blood does not mean MK-4 does nothing. It may be taken up quickly by tissues and used. Serum levels are only one way to look at it.
Blood levels and markers are not the same as outcomes such as fractures or heart events.

The osteocalcin marker, explained

Much of the research uses undercarboxylated osteocalcin (ucOC) as a marker. Osteocalcin is a protein involved in bone mineralization, and it needs vitamin K to be “carboxylated,” meaning activated so it can bind calcium. When more of it is undercarboxylated, that suggests vitamin K supply to bone may be lower. The 2021 review says the dose needed to lower ucOC was six times lower for MK-7 than for MK-4. A 2020 review adds that MK-7 at 90 to 180 micrograms a day promoted osteocalcin carboxylation, while MK-4 at nutritional doses such as 60 micrograms a day was ineffective in the human studies it cited.

This is the core reason many supplements, including ours, use MK-7. It works on this marker at doses that fit in a small daily capsule.

What the research shows for bone health

The evidence differs by form and is honest to call limited to mixed.

MK-4: The NIH fact sheet says trials in Japan found MK-4 supplementation reduced fracture rates, though findings from other trials have been mixed. Those Japanese trials used pharmacological doses. The 2020 review notes that 45 mg a day of MK-4 for three years improved some femoral bone-quality indices but did not improve bone mineral density. That dose is about 500 times larger than the MK-7 doses above, and it is a drug-level intake rather than a typical supplement.

MK-7: According to the NIH, a trial gave postmenopausal women 180 mcg a day of MK-7 for three years and found improved bone strength and less loss of lower-thoracic vertebral height. Findings like this are discussed in guides on supplements by life stage for women, where bone support becomes a larger concern after menopause. One trial in one population is encouraging, not conclusive.

The 2021 review states plainly that evidence is not yet sufficient to set recommended forms or doses for osteoporosis. So the fair summary is that vitamin K2 may support bone health, MK-7 has a practical edge at low doses, and no one can call either form a proven winner.

What the research shows for bone health — overview diagram

Why K2 is often paired with vitamin D3

Vitamin D helps your body absorb calcium. Vitamin K-dependent proteins help direct where calcium ends up. That is why the two are often combined in one formula. If you are building a plan around bone support, you can browse our Bone & Joint Stack, and our Vitamin K2 (MK-7) + D3 5,000 IU is the single-formula option. Ask your clinician about vitamin D dosing and your blood levels, since high D intakes are not right for everyone.

What the research shows for heart health

Heart health is where claims run ahead of the evidence, so we will be precise.

Observational studies link higher menaquinone intake to lower coronary calcification and lower heart disease mortality. But the NIH states that clinical trials of vitamin K supplementation for vascular calcification or heart disease remain inconclusive. Observational links cannot show cause, because people who eat more fermented foods and animal foods differ in many other ways.

There is one encouraging trial result. A 3-year randomized trial in postmenopausal women using 180 mcg a day of MK-7 reported a significant decrease in a measure of arterial stiffness (Stiffness Index beta), mainly in those who started with higher stiffness. That is a surrogate measure, not heart attacks or strokes. The 2021 review adds that the observed associations involve long-chain menaquinones, but that does not establish that either MK-7 or MK-4 protects the heart, and clinical guidelines for form and dose do not exist.

So if your goal is cardiovascular support, K2 is one possible piece, alongside diet, activity, and what your doctor advises. It is not a stand-in for any of those.

MK-7 or MK-4: how to choose

Use these criteria rather than a single winner.

Dose you can realistically take. MK-7 has human data at 90 to 180 mcg a day. MK-4 trials with bone outcomes used about 45 mg a day, which is not a typical supplement dose and is better discussed with a physician.
Convenience. Because MK-7 lasts longer in the blood, one daily capsule is practical. Short-lived MK-4 would need multiple doses to maintain levels.
Your diet. If you eat natto regularly, you already get MK-7. If you eat eggs, butter and meats, you get some MK-4, and your body also makes some from K1 in leafy greens.
Evidence for your goal. For bone markers at low doses, MK-7 has the clearer record. For the specific high-dose fracture trials from Japan, MK-4 is the form studied.
Your medications and health conditions. This can override everything else. See the next section.

Some products combine both forms. There is little head-to-head research showing a combination beats MK-7 alone, so we would not choose on that basis.

What to look for on a label

The form named explicitly (“menaquinone-7” or “MK-7”), not just “vitamin K2”.
The amount in micrograms per serving, so you can compare with the 90 to 180 mcg range studied.
A fat-containing meal at the time you take it, since vitamin K is fat-soluble.
Third-party testing or GMP manufacturing information.

Safety: who needs to check first

Vitamin K has low potential for toxicity. The Food and Nutrition Board did not set a Tolerable Upper Intake Level, and the NIH reports no adverse effects from vitamin K in food or supplements in humans or animals. Side effects, when they happen, tend to be minor stomach upset or a skin rash.

Low toxicity is not the same as safe for everyone. Please take these seriously:

Warfarin and similar anticoagulants. Vitamin K can interact seriously with warfarin. The NIH says people on these drugs need consistent vitamin K intake from food and supplements, because sudden changes can raise or lower the anticoagulant effect. Do not start, stop or change a K2 supplement without your prescriber or anticoagulation clinic, who may adjust monitoring.
Fat absorption medicines. Bile acid sequestrants and orlistat can reduce vitamin K absorption. Talk with your pharmacist about timing.
Pregnancy, nursing, or a chronic condition. Check with your clinician before starting any new supplement.
Children. Do not give supplements without a pediatrician’s advice.

If you are on any prescription medication, bring the product label to your appointment.

Our perspective

We formulate our K2 around MK-7 for three reasons. It has human data at doses small enough to put in a daily capsule. Its long presence in the blood suits a once-a-day routine. And the research behind it uses amounts we can disclose openly on the label. We think you should be able to compare the dose in your bottle with the dose in the studies.

We also think it is worth being plain about limits. The strongest MK-4 results come from pharmacological doses that do not resemble a supplement. The MK-7 bone and arterial stiffness findings come from a small number of trials in postmenopausal women. Neither form is a treatment for any condition, and we do not present K2 that way. What the evidence supports is that K2 contributes to the normal function of vitamin K-dependent proteins, which are involved in bone and calcium handling.

If you are comparing options, read the label and the studies behind it. That is the same standard we hold ourselves to.

— Kikaboni

Build your K2 routine with Kikaboni

If MK-7 fits your goals, our Vitamin K2 (MK-7) + D3 5,000 IU pairs the two nutrients in one formula, and our Bone & Joint Stack is for those building a broader plan. You can take the quiz on kikaboni.com to see which products match your goals, and we offer one-time and subscription purchase options. Check with your clinician first if you take anticoagulants.

FAQ

Is MK-7 the same as vitamin K2?

Not exactly. MK-7 is one form of vitamin K2, which is a group of menaquinones. MK-4 is another form in the same group. When a label says only “vitamin K2”, check the ingredient panel for which form it contains.

Is MK-7 better than MK-4?

It depends on the goal. MK-7 lasts longer in the blood and affected osteocalcin at lower doses in the studies reviewed, so it is practical for daily use. MK-4 has been studied at very high doses in Japan, with mixed results elsewhere. Reviews say evidence is insufficient to name a best form for osteoporosis or heart conditions.

Is there a downside to vitamin K2?

For most healthy adults, side effects are uncommon and usually mild, such as stomach upset or a rash, and no upper intake level has been set. The main concern is interaction with warfarin and similar blood thinners. Medicines that reduce fat absorption can also lower vitamin K absorption.

Is vitamin K2 good for your heart?

Observational studies link higher menaquinone intake with better heart outcomes, but clinical trials on vascular calcification and heart disease are inconclusive. One three-year trial of MK-7 found lower arterial stiffness in postmenopausal women, which is a surrogate marker. Treat K2 as one possible supporting factor, and follow your doctor’s guidance.