Written by the Plenthera team (orthomolecularly trained). Scientifically reviewed in April 2026. Last updated: April 30, 2026.
Vitamin K is not a single molecule but a family. K1 (phylloquinone) comes from green leafy vegetables and primarily regulates blood clotting. K2 (menaquinone) comes from animal and fermented foods—especially Japanese natto—and has its own role: it activates proteins that direct calcium to bones and teeth, away from soft tissues. At Plenthera, you'll find vitamin K in all relevant forms: K1 for classic blood clotting function, K2 as MK-7 (long-acting) for bone and vascular health, and combined with D3 for maximum calcium routing.
Which vitamin K is right for you?
| Form | Half-life | Best for |
|---|---|---|
| K2 MK-7 | 72 hours | Bone/vascular theme, low dosage effective |
| D3 + K2 MK-7 | Synergy | Premium bone/cardiovascular stack |
| K1 phylloquinone | Short | Specific blood clotting pathway |
| K2 MK-4 | 1-2 hours | High doses for specific purposes |
| K-complex (K1 + MK-4 + MK-7) | Variable | Complete K-profile |
What is vitamin K?
Vitamin K is a fat-soluble vitamin in two main forms: K1 (phylloquinone, plant-based) and K2 (menaquinone, animal-based and from fermentation). K2 consists of sub-forms MK-4 (short-acting) and MK-7 (long-acting). Vitamin K is essential for blood clotting and activates proteins that regulate calcium routing to bones and teeth.
Vitamin K was discovered in 1929 by the Danish scientist Henrik Dam—hence the letter K (from the German "Koagulation"). For a long time, it was only known for its role in blood clotting. It wasn't until the 1970s-90s that it became clear that vitamin K2 has a second, fundamentally different function: it activates specific proteins (osteocalcin, matrix-Gla-protein, MGP) that regulate calcium routing in the body.
The most important distinction within vitamin K is K1 versus K2. K1 (phylloquinone) is found in green leafy vegetables—kale, spinach, broccoli, parsley. It is absorbed by the liver and used for blood clotting. K2 (menaquinone) comes from animal products (egg yolk, cheese, liver, grass-fed butter) and from fermentation—especially Japanese natto, which is by far the highest natural source of MK-7. K2 is distributed systemically throughout the body and reaches bones, teeth, blood vessels—in the places where calcium routing is relevant.
The subdivision of K2 into MK-4 and MK-7 is practically important. MK-4 has a short half-life (1-2 hours) and requires high doses to reach steady-state—up to 45 mg/day in clinical research. MK-7, on the other hand, has a half-life of approximately 72 hours—lower doses (90-200 µg/day) achieve stable blood levels. For most users, MK-7 is therefore the more logical route. Also check out our vitamin D category for the crucial D3+K2 synergy and our magnesium category for the bone cofactors.
Vitamin K and EFSA — what is scientifically recognized?
Vitamin K has two clear EFSA-recognized claims, included in EU Regulation 432/2012:
"Vitamin K contributes to normal blood clotting."
"Vitamin K contributes to the maintenance of normal bones."
Threshold: claims apply with a daily intake of at least 15% RI—which is 11.25 µg of vitamin K per serving. Our products typically provide 75-200 µg per serving, well above the threshold.
The vitamin D + K2 + magnesium synergy
For bone health, vitamin D3, K2, and magnesium form a logical trio:
Vitamin D3: Increases calcium absorption from food through the intestinal wall. Without sufficient D3, absorption is suboptimal—even with high calcium intake.
Vitamin K2 (MK-7): Activates osteocalcin—a protein that binds calcium to the bone matrix. Also activates matrix-Gla-protein (MGP) which inhibits calcium deposition in blood vessel walls. Without sufficient K2, calcium can be "misrouted."
Magnesium: Cofactor in vitamin D activation (liver and kidneys). Without sufficient magnesium, D3 supplementation works suboptimally.
Many premium formulas offer D3 + K2 (MK-7) combined. For those who want to maximize support for bone and cardiovascular health, the trio of D3 + K2 + magnesium is a logical stack. Check out our vitamin D category for combined D3+K2 products.
The vitamin K forms at Plenthera
Vitamin K2 MK-7 (from natto fermentation)
The long-acting K2 form—half-life 72 hours, low doses (90-200 µg) sufficient for steady-state. Our first-line recommendation. Premium standards: MenaQ7®, Vitamk7®.
Vitamin D3 + K2 (combined)
Synergistic combination for bone and cardiovascular health. Also check out our vitamin D category for the broader context. Doses typically 25-75 µg D3 + 75-200 µg K2.
Vitamin K1 (phylloquinone)
Classic form—for those who specifically want to support the blood clotting role. Plant-based, from alfalfa extract.
Vitamin K2 MK-4
The short-acting form from animal sources. Requires higher doses for effect.
Vitamin K-complex (K1 + K2 MK-4 + K2 MK-7)
Premium formula with all three forms for a complete K-profile.
How to use vitamin K?
Simple basic approach for vitamin K:
- Determine your goal: bone and cardiovascular health (K2 MK-7), classic blood clotting function (K1), or complete profile (K-complex).
- For general supplementation: 75-200 µg K2 MK-7 per day.
- Combine with vitamin D3 (25-75 µg) for the crucial calcium-routing synergy.
- Consider magnesium cofactor (200-400 mg) for optimal D activation.
- Always take with a fatty meal—vitamin K is fat-soluble.
- Timing is flexible; many users take K with their evening meal.
- With vitamin K antagonist anticoagulants (warfarin, phenprocoumon, acenocoumarol): DO NOT take without consulting a doctor or thrombosis service, in accordance with the advice of the NVWA.
- With DOACs/NOACs (apixaban, rivaroxaban, dabigatran): interaction is less critical—still consult.
Myths and misconceptions about vitamin K
Myth 1: "K2 MK-4 is always better than MK-7."
Incorrect for most users. MK-4 has a half-life of 1-2 hours—requires high doses (up to 45 mg/day in research) for steady-state. MK-7 with a 72-hour half-life achieves stable blood levels at 100-200 µg/day—thousands of times more efficient in terms of dosage.
Myth 2: "K2 is found in milk and dairy."
Half true. Conventional dairy contains little K2. Fermented cheese (Gouda, Edam, brie) contains MK-9. Butter from grass-fed cows contains some MK-4. For targeted K2 intake, a supplement or natto is more effective.
Myth 3: "Everyone who takes D3 needs K2."
Not automatically. At common D3 doses (25-50 µg/day), most people do not need acute K2 supplementation—sufficient from diet. At higher D3 doses (75-100 µg/day) or long-term use, K2 supplementation becomes more logical.
Myth 4: "Vitamin K is dangerous for people with blood clotting problems."
Nuanced. With vitamin K antagonists (warfarin, phenprocoumon): maintaining stable vitamin K intake is more important than avoiding it. Sudden changes (starting or stopping) disrupt the medication. Always consult the thrombosis service.
Combining vitamin K with other supplements
Vitamin K works synergistically with other fat-soluble vitamins and minerals for bone and cardiovascular health. Common combinations:
- Vitamin D3: crucial synergy—D3 increases calcium absorption, K2 directs calcium to bones/teeth.
- Magnesium: cofactor in D activation.
- Calcium: for specific bone health, provided in the correct ratio (~2:1 calcium:magnesium).
- Vitamin A: fat-soluble antioxidant, together with D and K a classic cod liver oil trio. Check out our fish oil category.
- Vitamin E: fat-soluble antioxidant.
- Multivitamin: for broad coverage with K2 incorporated.
Frequently Asked Questions
What is vitamin K?
Fat-soluble vitamin in two main forms: K1 (phylloquinone, plant-based) and K2 (menaquinone, animal/fermentation).
What is the difference between K1 and K2?
K1: green leafy vegetables, primarily blood clotting. K2: animal/natto, calcium routing to bones and teeth.
What is the difference between MK-4 and MK-7?
MK-4: short-acting (1-2 hour half-life), high doses needed. MK-7: long-acting (72 hour half-life), low doses sufficient.
How much vitamin K per day?
RI 75 µg/day. For broad supplementation, 75-200 µg K2 MK-7. No UL established for K1/K2.
What does K2 do with vitamin D?
D3 increases calcium absorption; K2 activates osteocalcin and MGP which route calcium to bones/teeth, away from soft tissues.
Does vitamin K help bones?
EFSA-recognized claim: vitamin K contributes to the maintenance of normal bones.
When to take vitamin K?
With a fatty meal for optimal absorption. Timing flexible.
Can K2 be taken with blood thinners?
With vitamin K antagonists (warfarin, acenocoumarol, phenprocoumon): DO NOT take without consulting a doctor or thrombosis service.
Vegan vitamin K2—does it exist?
Yes. K2 MK-7 from Bacillus subtilis natto fermentation is plant-based (fermented on soy). No animal production.
What is natto?
Japanese fermented soybean product. Contains ~1,000 µg MK-7 per serving—by far the highest natural source.
Sources
- EFSA Regulation (EU) 432/2012 — vitamin K claims.
- EFSA NDA Panel — Dietary Reference Values for vitamin K (2017).
- Schurgers LJ. & Vermeer C., "Differential lipoprotein transport pathways of K-vitamins in healthy subjects", Biochim Biophys Acta (2002).
- Sato T. et al., "Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women", Nutr J (2012).
- Knapen MH. et al., "Three-year low-dose menaquinone-7 supplementation helps decrease bone loss", Osteoporos Int (2013).
Disclaimer: This text is for informational purposes only and does not replace medical advice. Vitamin K is a dietary supplement, not a medicine. In case of doubt or medication use, we recommend consulting a doctor or orthomolecular therapist first.