If you’ve looked at the label on a vitamin D3K2 supplement, you’ll have seen either “MK-4” or “MK-7” listed next to the K2. Most people ignore it and assume K2 is K2. But the form in your supplement affects how long it stays active in your body, and whether a single daily dose is actually doing what you think it is.
This is a practical question with a clear answer. Here’s what the research shows.
Table of Contents
MK4 and MK7 are both forms of vitamin K2
Vitamin K2 is a family of compounds called menaquinones. MK4 and MK7 are the two you’ll find in most supplements. The numbers refer to the length of their molecular side chains (4 and 7 isoprene units respectively).
Both forms activate the same key proteins: osteocalcin, which anchors calcium into bone, and Matrix Gla Protein (MGP), which prevents calcium from depositing in artery walls. The biological mechanism is the same. Where they differ is in how long they stay active once you’ve taken them.
The half-life difference
This is the most practically important distinction between MK4 and MK7.
MK4 has a half-life of around 1 to 4 hours. It’s absorbed, peaks in the blood quickly, and clears just as fast. To maintain consistent levels, you’d need to take it multiple times throughout the day.
MK7 has a half-life of approximately 72 hours. A single daily dose maintains stable blood levels through the day and overnight, which is how standard supplement doses are designed to work.
A 2012 study by Schurgers et al., published in Biochimica et Biophysica Acta, confirmed MK7’s superior ability to raise and sustain blood K2 levels compared to MK4 at equivalent doses. For anyone taking a once-daily D3K2 capsule, MK7 is the more appropriate form.
Where do MK4 and MK7 come from?
MK4 is found naturally in animal products: meat, eggs, dairy, and certain cheeses. It’s also produced synthetically, which is how most MK4 in supplements is sourced.
MK7 comes primarily from fermented foods. Natto, a Japanese dish made from fermented soybeans, is by far the richest dietary source. Supplement-grade MK7 is typically produced via controlled fermentation using Bacillus subtilis, the same bacteria responsible for natto fermentation.
This distinction matters beyond origin. As covered below, the production method directly affects the isomeric quality of the MK7, which has real implications for whether the K2 in your supplement is actually biologically active.
What the research shows on bones and arteries
Most human supplementation studies on vitamin K2 have used MK7, not MK4.
The Knapen et al. trial, published in Osteoporosis International (2013), found that 180mcg of MK7 daily for three years significantly improved bone strength and slowed bone loss in postmenopausal women. The Rotterdam Study (Geleijnse et al., Journal of Nutrition, 2004) found that higher dietary intake of menaquinones, predominantly MK7 from fermented foods, was associated with a substantially reduced risk of coronary heart disease.
MK4 does have clinical evidence behind it, but at much higher doses. In Japan it has been used pharmaceutically for osteoporosis at 45mg daily, roughly 450 times the dose found in a typical supplement capsule. The evidence at microgram supplementation doses is much thinner than for MK7.
For more on how K2 fits into the broader picture of bone health, see our guide on why bone health matters and how to protect it.
Not all MK7 is equal: the all-trans question
This is where it gets more specific, and more relevant if you’re comparing quality supplements rather than just checking the form of K2.
MK7 can exist in two geometric configurations: trans and cis isomers. Only the all-trans form is biologically active. The trans configuration is how MK7 occurs naturally in fermented foods. Cis isomers don’t activate osteocalcin or MGP in the same way and are essentially inert from a health perspective.
Some MK7 supplements produced through certain manufacturing processes contain a mixture of trans and cis isomers. If your K2 isn’t predominantly all-trans, you’re getting less active compound per dose than the label implies, even if the total MK7 content looks correct.
High-quality MK7 produced through natural natto fermentation is predominantly all-trans. The European Food Safety Authority has referenced all-trans MK7 specifically in its assessments of menaquinone-7 safety and bioavailability. When assessing a D3K2 supplement, it’s worth checking that the K2 is stated as all-trans MK7, not just MK7.
Which form does Epsilon Life use?
Our Vitamin D3K2 supplement contains all-trans MK7 at 100mcg per capsule. We use fermentation-derived MK7 because the process naturally produces the all-trans configuration, and because MK7’s 72-hour half-life makes it suited to once-daily dosing without any guesswork about timing.
The 100mcg dose falls within the 75–180mcg range supported by European health authority guidance and aligns with the research used in the Knapen et al. bone health study. For a full breakdown of the formula, see our ingredient-by-ingredient explainer.
Frequently asked questions
Is MK7 better than MK4?
For daily supplementation, MK7 is the more practical choice. Its half-life of around 72 hours means a single daily dose maintains consistent blood levels, while MK4 clears in 1 to 4 hours and requires multiple doses to achieve the same effect. The human evidence on bone and cardiovascular health at typical supplement doses is also stronger for MK7 than MK4.
What does all-trans MK7 mean?
MK7 can exist in two geometric forms: trans and cis. Only the all-trans form is biologically active, meaning only this configuration activates osteocalcin and Matrix Gla Protein, the proteins that direct calcium into bone and away from artery walls. Cis isomers don’t have the same effect. All-trans MK7 is the form that occurs naturally in fermented foods and is produced by quality fermentation-based manufacturing processes.
How much MK7 should I take per day?
Research on bone health has used doses between 90mcg and 180mcg daily. European health guidance references 75–180mcg as the appropriate daily range for MK7 supplementation. See our full vitamin D3 and K2 dosage guide for more detail on how to structure your intake.
Can I get enough K2 from food?
The richest dietary source of MK7 is natto, which contains up to 1,000mcg per 100g. Most Western diets contain very little. Hard cheeses provide some MK4, but typically well below supplementation doses. For people who don’t eat natto regularly, supplementation is the practical route to consistent K2 intake.
Does it matter whether my D3K2 supplement contains MK4 or MK7?
For a once-daily supplement, yes. MK4’s short half-life means it may clear your system before your next dose, leaving a gap in K2 activity. MK7’s 72-hour half-life maintains coverage throughout the day. If your supplement uses MK7, also check whether the label specifies all-trans: that’s the biologically active form you’re looking for.
References
- Knapen MH et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International, 2013. doi:10.1007/s00198-013-2325-6
- Geleijnse JM et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. Journal of Nutrition, 2004. doi:10.1093/jn/134.11.3100
- Schurgers LJ et al. Differential lipoprotein transport pathways of K-vitamins in healthy subjects. Biochimica et Biophysica Acta, 2012. doi:10.1016/j.bbalip.2012.01.009
- European Food Safety Authority. Scientific Opinion on the safety of menaquinone-7 as a novel food ingredient. EFSA Journal, 2017. doi:10.2903/j.efsa.2017.4912
- Vermeer C. Vitamin K: the effect on health beyond coagulation, an overview. Food & Nutrition Research, 2012. doi:10.3402/fnr.v56i0.5329
This article is for informational purposes only and does not constitute medical advice. If you take anticoagulant medication such as warfarin, speak with your GP before adding vitamin K2 to your routine, as K2 affects blood clotting pathways.
