Vitamin K2: MK-4 vs MK-7, Doses, and Safety

Vitamin K is the name for a family of fat-soluble compounds. Vitamin K1 is phylloquinone. Vitamin K2 refers to menaquinones, which are numbered MK-4 through MK-13 according to the length of their side chain. MK-4 and MK-7 are the forms most often seen on supplement labels. ¹

Vitamin K acts as a cofactor for enzymes that activate vitamin-K-dependent proteins involved in blood clotting, bone metabolism, and other functions. That biology applies to the vitamin K family. It is therefore misleading to present K1 as only the clotting form and K2 as a form that acts only in bone or arteries. ¹

Phylloquinone is the main dietary form of vitamin K and is concentrated in leafy green vegetables and plant oils. Menaquinones occur in varying amounts in fermented and animal-derived foods. MK-4 is also produced in the body from phylloquinone. ¹

NIH notes that MK-7 remains in circulation longer than phylloquinone in a small supplement comparison. That pharmacokinetic difference may affect exposure and product design, but it does not prove that MK-7 produces better fracture, cardiovascular, or other clinical outcomes than MK-4. ¹

Do not rank forms from the name alone

A clearly disclosed form is easier to interpret than a vague complex. Clear disclosure is not proof that one form is universally superior. Direct clinical comparisons of MK-4 and MK-7 are limited, and studies have used very different doses, populations, durations, and outcomes.

What recent trials found

In a three-year randomized trial, 375 mcg MK-7 added to calcium and vitamin D improved osteocalcin carboxylation in postmenopausal women with osteopenia but did not improve bone mineral density, bone turnover markers, or bone microarchitecture compared with placebo. ⁶

A 2022 randomized trial found that 720 mcg MK-7 plus vitamin D for two years did not slow aortic valve, aortic, or coronary calcification in older men with aortic valve calcification. ⁷

A 2026 randomized trial found that 360 mcg of MK-7 per day for two years was associated with slower coronary artery calcium progression than placebo in adults with symptomatic coronary artery disease. Coronary calcium still increased in both groups. The clinical significance remains uncertain, and effects on heart attacks, strokes, cardiovascular deaths, or other clinical outcomes have not been established. ⁸

Together, these findings support careful wording: K2 is being studied for bone and vascular outcomes, but it is not an established plaque-removal or disease-prevention treatment. The popular phrase that K2 directs calcium into bones and away from arteries turns a biological hypothesis into a stronger clinical promise than current evidence supports.

There is no separate official recommended intake for vitamin K2. U.S. Adequate Intakes for vitamin K are 120 mcg per day for adult men and 90 mcg per day for adult women, including during pregnancy and lactation. These values were derived primarily from phylloquinone intake data and do not establish a separate MK-4 or MK-7 requirement or supplement dose. ¹

The current U.S. Daily Value for vitamin K is 120 mcg. FDA has stated that this reference is based on the Adequate Intake for phylloquinone and that MK-7 should be listed as a dietary ingredient without an established Daily Value. A percentage Daily Value is a label reference, not proof of a clinically effective K2 dose. ^{2, 3}

A practical vitamin K2 label check

Convert units before comparing amounts. For example, 5 mg of MK-4 equals 5,000 mcg. This makes the arithmetic comparable, but it does not make MK-4 and MK-7 clinically interchangeable or establish that either amount is appropriate.

1. Confirm the form, serving size, and amount per full serving.
2. Keep micrograms and milligrams separate. One milligram equals 1,000 micrograms.
3. Check whether K1 and K2 amounts are disclosed separately in a combination.
4. Treat a Daily Value as a label reference, not as a K2 outcome or safety claim.
5. Record vitamin D3, calcium, and other active amounts separately.
6. Do not start, stop, or change K2 when using a vitamin K antagonist without the clinician managing that medicine.

For the wider method, read How to Read Supplement Labels.

A familiar number does not establish the same form, the same K2 amount, or the same evidence context. Read the ingredient name and source line before treating two labels as equivalent.

Phylloquinone is concentrated in leafy green vegetables and plant oils. Menaquinones occur in smaller and more variable amounts in fermented and animal-derived foods; natto is a notable source of MK-7. Food composition, serving size, and dietary pattern matter when considering total vitamin K intake. ¹

Vitamin K is fat-soluble and is absorbed with processes that also handle dietary fat. People with fat-malabsorption disorders, certain gastrointestinal conditions, or a history of bariatric surgery can have different vitamin K needs and may require clinical monitoring. ¹

Vitamin K2 can seriously interfere with warfarin and other vitamin K antagonist medicines such as acenocoumarol and phenprocoumon. The concern is not limited to K1. Changes in vitamin K intake can change the anticoagulant effect, so intake needs to be consistent and supplement changes need to be managed by the clinician monitoring the medicine. This direct mechanism should not be generalized to every anticoagulant, but anyone using a prescription anticoagulant should still review a new supplement with the relevant clinician or pharmacist. ^{1, 9}

In a controlled study of people anticoagulated with acenocoumarol, MK-7 doses as low as 10 mcg affected anticoagulation sensitivity in some participants. This does not provide a universal interaction threshold, but it shows why a retail K2 dose must not be assumed safe with a vitamin K antagonist. ⁹