Vitamin K2 MK-4 vs MK-7: What the Difference Means

MK-4 and MK-7 share the vitamin K2 core, but side-chain length changes blood exposure after dosing ⁴.
MK-7 products are usually labeled in micrograms, while MK-4 products are usually labeled in milligrams ².
Warfarin and similar vitamin K blockers require medical guidance before changing vitamin K intake ¹.

The label number that tricks people

A vitamin K2 label can show MK-7 100 mcg next to MK-4 5 mg, and the smaller number may look weaker. It is not that simple. Micrograms and milligrams are different units. One milligram equals 1,000 micrograms, so 5 mg of MK-4 is 5,000 mcg. The real surprise is that the larger MK-4 amount does not automatically mean a stronger or longer effect.

Same vitamin job, different travel pattern

Vitamin K helps the body finish certain proteins so they can bind calcium properly. This matters for normal blood clotting and for proteins involved in bone metabolism. The Office of Dietary Supplements describes vitamin K as needed for proteins involved in blood clotting, bone metabolism, and other functions. EFSA has also accepted vitamin K claims for normal blood coagulation and maintenance of normal bone.

MK-4 and MK-7 are both menaquinones, meaning forms of vitamin K2. The number tells you about the side chain attached to the vitamin K structure. MK-4 has a shorter side chain. MK-7 has a longer one. That small chemical difference changes how each form is carried in fat particles after a meal, how long it can be detected in blood, and how supplement doses are usually designed.

MK-4 is unusual because human and animal tissues can make it from vitamin K1, the form found in leafy greens. NIH notes that MK-4 is produced by the body from phylloquinone, also called vitamin K1, through a non-bacterial conversion process. MK-4 is also used in Japan as menatetrenone, a high-dose prescription form studied for bone-related outcomes. That medical dose pattern is usually measured in milligrams, not micrograms.

MK-7 is the form people often associate with natto, a fermented soybean food. In supplement studies, MK-7 generally stays detectable in blood longer than MK-4. A human comparison study found nutritional MK-7 produced a more sustained blood response than MK-4 at the tested doses. A review of vitamin K forms reported that vitamin K1 and MK-4 remain in plasma for about 8 to 24 hours, while longer-chain menaquinones can be detected up to 96 hours after intake.

The useful decision

If you are choosing an ordinary daily supplement and are not on a vitamin K blocking blood thinner, the practical label move is simple: do not compare MK-4 and MK-7 by dose number alone. First identify the form. If the label says MK-7, expect a microgram amount and usually once-daily use. If it says MK-4, expect a larger milligram amount, especially when the product is copying clinical menatetrenone-style dosing.

The strongest next step today is to check the “Supplement Facts” panel for the exact form: “K2 as MK-7,” “K2 as MK-4,” “menaquinone-7,” “menaquinone-4,” or “menatetrenone.” If the product only says “vitamin K2” without naming the form, choose a clearer label.

Deep dive

How it works

Vitamin K dependent proteins are made in an unfinished form first. Vitamin K helps add a small chemical group to specific protein sites, which lets those proteins bind calcium. In plain terms, the protein’s shape and charge are changed so calcium can attach where it is supposed to. MK-4 and MK-7 can both feed this vitamin K cycle, but their fat solubility and side-chain length affect how they move in blood after digestion.

When you'll see this

The term in the wild

You pick up a bone-support supplement that says “Vitamin K2 as MK-7, 100 mcg.”

The key detail is “as MK-7,” not just the 100 mcg number. MK-7 is commonly dosed in micrograms because it has a longer blood presence than MK-4 in human studies.

You avoid rejecting the product just because the number looks small next to milligram MK-4 products.
A different product says “Vitamin K2 as MK-4, 5 mg.”

That equals 5,000 mcg, but it is not automatically 50 times “stronger” than 100 mcg MK-7. MK-4 is handled differently and is often used in larger amounts.

You compare form and dosing pattern, not just the biggest number on the label.
You read a Japanese study using menatetrenone for bone outcomes.

Menatetrenone is MK-4, usually used as a medicine-style high-dose form in that research context. It should not be casually equated with low-dose over-the-counter K2 products.

You avoid importing a prescription-dose research conclusion into a standard supplement decision.
You eat natto and then look at a K2 supplement made from fermentation.

Natto is a natural food source strongly associated with MK-7. Fermented K2 supplements often highlight MK-7 for this reason.

You can connect the food source, the label term, and the form being studied.

Myths vs reality

What people get wrong

Myth

MK-7 is better because it has a higher number.

Why people believe it Supplement labels use shorthand such as MK-4 and MK-7 without explaining that “MK-n” means the number of repeating side-chain units, not quality.

Reality

The 7 only describes the length of part of the molecule. It is not a score, grade, or potency rating.
Myth

A bigger MK-4 dose means more vitamin K effect than a smaller MK-7 dose.

Why people believe it Labels put mcg and mg values in the same box, and many readers miss that 1 mg equals 1,000 mcg.

Reality

Dose size and body exposure are not the same thing. MK-7 usually produces a longer blood pattern, while MK-4 often appears in larger milligram amounts.
Myth

Vitamin K2 supplements are only about bones, not blood clotting.

Why people believe it Bone-support marketing often highlights osteocalcin, a vitamin K dependent bone protein, while leaving out the broader vitamin K role described in nutrition references.

Reality

All vitamin K forms share the core vitamin K role of helping specific proteins become fully functional, including proteins involved in normal clotting.
Myth

Natural K2 means it cannot matter for medication users.

Why people believe it The word “natural” on supplement labels can make people forget that nutrients still change body chemistry.

Reality

Vitamin K intake can interfere with warfarin-style medicines because those drugs work by opposing vitamin K activity.

If you take warfarin, Coumadin, or another vitamin K blocking anticoagulant, the issue is not whether MK-4 or MK-7 is “better.” The issue is consistency. Do not start, stop, or switch vitamin K2 products without the clinician managing your clotting tests.

Frequently asked

Common questions

Should MK-4 and MK-7 be taken with food?

Yes. Vitamin K is fat soluble, so taking it with a meal that contains some fat generally makes more sense than taking it on an empty stomach.

Why do some labels say “all-trans MK-7”?

“All-trans” describes the molecule’s shape. For MK-7, this matters because the intended active form is the all-trans form, not a mixed or poorly specified form.

Can I get MK-7 from food instead of a capsule?

Yes. Natto is the best-known food source of MK-7, although its taste and availability make supplements more practical for some people.

Does vitamin D change how I should think about K2?

Vitamin D and vitamin K are often paired in bone-support products because they relate to calcium handling in different ways. That does not mean every vitamin D user needs K2, and it does not remove the medication caution for vitamin K.

How long does it take to “feel” vitamin K2 working?

Most people should not expect a felt effect. Vitamin K2 is usually judged by diet pattern, supplement form, medication context, and research markers rather than immediate sensations.

Sources

Vitamin K2: MK-4 vs MK-7 in brief

What Vitamin K2: MK-4 vs MK-7 means

The label number that tricks people

Same vitamin job, different travel pattern

The useful decision

Putting Vitamin K2: MK-4 vs MK-7 to work

Sources