Written by the Plenthera team (trained in orthomolecular nutrition). Scientifically reviewed in October 2026. Last updated: 6 October 2026.
Vitamin K is a fat-soluble vitamin needed for normal blood clotting and for strong bones. There are two main forms: K1 from green vegetables and K2 from fermented and animal products. At Plenthera you will find vitamin K2 mainly in combination with vitamin D3: D3 + K2 from Plent and Vitals, KD Ultra from Arthur Andrew Medical with K1 and two K2 forms, and the Bot en Tandformule Pro from Vitals.
Which vitamin K suits you?
Overview of the common forms of vitamin K on the market. At Plenthera we currently stock vitamin K2 in combination with vitamin D3.
| Form | Vitamin K per serving | Best for |
|---|---|---|
| K2 (MK-7) + D3 (at Plenthera) | 75–90 µg | Daily combination for the bones |
| K1 + K2 (MK-4 and MK-7) + D3 (at Plenthera) | over 1,700 µg | High-dose formula with several forms of K |
| K2 in a bone formula (at Plenthera) | 180 µg | With calcium, magnesium, D3 and silicon |
| Individual K2 (MK-7) | 45–200 µg | Without vitamin D |
| Individual K1 | varies | Targeted K1 supplementation |
What is vitamin K?
Vitamin K is a group of fat-soluble vitamins. The body needs vitamin K to activate clotting proteins and proteins in bone, such as osteocalcin.
The name comes from the German 'Koagulation' (clotting). Vitamin K1 (phylloquinone) is found mainly in green leafy vegetables such as kale, spinach and broccoli. Vitamin K2 (menaquinones) is found in fermented products such as natto and cheese, and in egg yolk and meat; gut bacteria also make some of it. Deficiency is rare in adults. Newborn babies have little vitamin K; that is why in the Netherlands they are given vitamin K at birth and breastfed babies are then given vitamin K drops daily.
In addition to clotting, the role of vitamin K in retaining calcium in bone and in preventing calcification in the blood vessels is being researched. Population studies have found associations between a higher K2 intake and less vascular calcification; whether supplementation has the same effect is still being researched.
Vitamin K and EFSA – what is scientifically recognised?
The following health claims are authorised for vitamin K (Regulation (EU) 432/2012):
"Vitamin K contributes to normal blood clotting."
"Vitamin K contributes to the maintenance of normal bones."
The claims apply to products that provide at least 15% of the reference intake (75 µg) per daily serving, i.e. at least 11.25 µg vitamin K. This applies to all products in this category.
K1, MK-4 or MK-7 – what is the difference?
K1 (phylloquinone): the form from green vegetables. Mainly used in the liver for clotting and stays in the blood relatively briefly.
K2 as MK-4 (menaquinone-4): a short K2 form from animal products. Quickly taken up from the blood into tissues; in supplements usually used at higher dosages.
K2 as MK-7 (menaquinone-7): a long K2 form from natto. In studies it stays in the blood much longer than K1 and MK-4, so one low dose per day is sufficient. Most K2 supplements contain MK-7, often in the all-trans form.
Vitamin K at Plenthera and other forms on the market
Vitamin K2 with D3 – at Plenthera
D3 + K2 (MK-7) from Plent (90 capsules) provides 75 µg vitamin K2 and 50 µg vitamin D3 per capsule. Vitamine K2 + D3 from Vitals (60 softgels) contains 90 µg K2 (MK-7, K2VITAL) and 25 µg D3 from algae per softgel. KD Ultra from Arthur Andrew Medical (90 capsules) combines, per capsule, 100 µg K1, 1,500 µg K2 as MK-4 and 110 µg as MK-7 with 62.5 µg D3 from lichen. Ionic D3 + K2 from Trace Minerals (59 ml) contains 100 µg K2 per serving of 4 drops; please note: that serving also provides 125 µg vitamin D, more than the safe upper limit of 100 µg. Only use this product in consultation with your doctor.
Vitamin K2 in a bone formula – at Plenthera
Bot en Tandformule Pro from Vitals (60 tablets) provides, per 2 tablets, 180 µg K2 (MK-7), 50 µg D3, 200 mg calcium, 100 mg magnesium and silicon.
Other forms on the market
Individual K2 (MK-7) without vitamin D, individual K1 and natto as a food. We do not currently stock these. Vitamin K is also found in many multivitamins.
How do you use vitamin K?
- Do you use coumarin-type anticoagulants (acenocoumarol, phenprocoumon)? Then do not use a vitamin K supplement without consulting your doctor or anticoagulation clinic.
- Follow the dosage on the label.
- Take vitamin K with a meal that contains some fat; it is fat-soluble.
- With combination products, also watch the vitamin D: add up vitamin D from several products and stay below the safe upper limit of 100 µg per day.
- Are you pregnant or breastfeeding? Then consult your midwife or doctor first.
Myths and misconceptions about vitamin K
Myth 1: "Those who eat a lot of vegetables have enough K2."
Vegetables mainly provide K1. K2 comes from fermented and animal products. Whether that difference matters for health is still being researched; both forms contribute to the maintenance of normal bones.
Myth 2: "Vitamin K2 reverses arteriosclerosis."
Not demonstrated. There are population studies that link a higher K2 intake to less vascular calcification, but it has not been proven that supplementation reverses existing calcification.
Myth 3: "Vitamin K thickens your blood."
In healthy people, extra vitamin K does not cause excessive clotting. It can, however, reduce the effect of coumarin anticoagulants.
Combining vitamin K with other supplements
- Vitamin D: vitamin D contributes to normal absorption/utilisation of calcium and phosphorus.
- Calcium: calcium is needed for the maintenance of normal bones.
- Magnesium: magnesium contributes to the maintenance of normal bones.
- Strong bones: all supplements around the theme of bones in one place.
Frequently asked questions
What is the difference between vitamin K1 and K2?
K1 (phylloquinone) is found mainly in green leafy vegetables. K2 (menaquinones) comes from fermented products such as natto and cheese and from animal products, and is partly made by gut bacteria. Both contribute to normal blood clotting and to the maintenance of normal bones.
What is MK-7?
MK-7 (menaquinone-7) is a form of vitamin K2 that occurs naturally in natto. In studies it stays in the blood longer than K1 and MK-4, so one dose per day is sufficient.
Can I use vitamin K with blood thinners?
Not without consultation. Vitamin K can reduce the effect of coumarin-type anticoagulants (acenocoumarol, phenprocoumon). If you use these medicines, always consult your doctor or anticoagulation clinic first.
Why is vitamin K2 often combined with D3?
Both contribute to the maintenance of normal bones. Vitamin D contributes to the normal absorption of calcium, vitamin K is needed for proteins that bind calcium in bone.
Does vitamin K have an upper limit?
EFSA has not set a safe upper limit for vitamin K, because no adverse effects of high intakes are known in healthy people. This is different for users of coumarin anticoagulants.
When is the best time to take vitamin K?
Vitamin K is fat-soluble. Take it with a meal that contains some fat, at the dosage on the label.
Sources
- Regulation (EU) 432/2012 – list of permitted health claims.
- EFSA NDA Panel (2017) – Dietary reference values for vitamin K. EFSA Journal 15(5):4780.
- Voedingscentrum (Netherlands Nutrition Centre) – Vitamin K.
- Schurgers LJ et al. (2007). Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood 109(8):3279–3283.
- Geleijnse JM et al. (2004). Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr 134(11):3100–3105.
Disclaimer: This text is for informational purposes only and does not replace medical advice. Vitamin K is a food supplement, not a medicine. If in doubt or if you take medication, we recommend consulting a doctor or orthomolecular therapist first.