Vitamin K2 is a group of fat-soluble forms of vitamin K called menaquinones, found in fermented foods, animal foods and supplements. On a label you will mostly meet MK-7, usually 50 to 100 µg per daily dose, often paired with vitamin D3. The EU reference intake (NRV) for vitamin K is 75 µg a day.
Below we explain how K2 differs from K1, what MK-4 and MK-7 mean, how to read the microgram figure and who must talk to a doctor before taking it. The warfarin warning matters most in practice, so it sits in a box right after the dose section.
Vitamin K1 and K2: what is the difference
"Vitamin K" is a family of compounds. Plants make K1 (phylloquinone), the main form in food, found mostly in leafy greens and vegetable oils. K2 is a set of menaquinones, written MK-4 to MK-13. Bacteria make them, so they appear in fermented foods such as natto and some cheeses, and in smaller amounts in eggs and meat. Bacteria in the human gut also produce menaquinones, though how much of that is absorbed and used is not well established.
| Form | Other name | Where it comes from | In supplements |
|---|---|---|---|
| K1 | phylloquinone | leafy greens, vegetable oils | sometimes, often in multivitamins |
| K2 as MK-4 | menaquinone-4 | eggs, meat, dairy | less common |
| K2 as MK-7 | menaquinone-7 | natto and other fermented foods | the most common K2 form |
For EU labelling all of these count as "vitamin K". The authorised claims below are written for vitamin K, not for one form, so no claim says K2 does something that K1 does not.
MK-4 and MK-7: which one is on the label
Most D3 + K2 products use MK-7, and the label usually says it comes from Bacillus subtilis natto, a fermentation culture. MK-4 is the form found in animal foods. In pharmacokinetic studies MK-7 stays in the blood longer than MK-4, which is why one daily dose of MK-7 is common, while MK-4 products often split the dose. Treat that as a practical difference in dosing, not as proof that one form is better.
Look for "menaquinone-7" or "MK-7" in the ingredient list. A line that only says "vitamin K2" tells you less, so compare it with the micrograms.
How many micrograms: NRV and label doses
The NRV for vitamin K is 75 µg. EFSA's adequate intake for adults is 70 µg a day from food and supplements together. EFSA has not set an upper limit for vitamin K, because it found no adverse effects from high intakes of K1 or K2 in the data available. That is no reason to take large doses, and it does not cover interactions with medicines.
| Vitamin K on the label | % of the NRV (75 µg) |
|---|---|
| 50 µg | 67 % |
| 75 µg | 100 % |
| 100 µg | 133 % |
The health claims for vitamin K apply when a product provides at least 15% of the NRV per daily dose, which is about 11 µg. Every product in our D3 + K2 range clears that. Most give 100 µg of MK-7 a day. The VEGE tablet gives 50 µg per half tablet, the dose for healthy adults under 75, and 100 µg per whole tablet.
If you take warfarin, acenocoumarol or another vitamin K antagonist, do not start a supplement with vitamin K without your doctor's approval. Vitamin K changes how these medicines work, and the OstroVit labels in our range say they are not for people taking such anticoagulants. If you take any other blood-thinning medicine, ask your doctor or pharmacist too. The same applies when you are pregnant or breastfeeding, and these products are not for children.
Why K2 is paired with vitamin D3
Vitamin D and vitamin K each have their own authorised claims, and none of them links the two. Vitamin D contributes to normal absorption/utilisation of calcium and phosphorus. Vitamin D contributes to the maintenance of normal bones. Vitamin K contributes to the maintenance of normal bones. Vitamin K contributes to normal blood clotting.
That is the honest picture. Manufacturers combine them because both nutrients are discussed in connection with bones, and because someone who takes D3 every day can get K in the same tablet. A combined tablet means one product instead of two. It does not create a separate EU-approved effect, and the claims about arteries or "directing calcium" that you see online are not on the EU list.
Choose the vitamin D dose first. Our vitamin D range and the vitamin D3 4000 IU range come before the K2 decision. EFSA's upper level for vitamin D is 100 µg (4000 IU) a day for adults.
K2 in food: how much can you get
Natto is the richest food source of MK-7 by a wide margin, and it is rarely eaten outside Japan. Cheese, egg yolk, butter and meat give smaller amounts of MK-4 and other menaquinones. K1 from leafy greens covers most of the vitamin K that people eat. If your diet has few of these foods, a supplement is one way to fill the gap.
How to take vitamin K2
Vitamin K is fat-soluble, so take it with a meal that contains some fat. Take it at the same time each day and keep the amount steady, which matters if you use any medicine that interacts with it. Do not exceed the dose on the label.
If you miss a day, do not double up the next day, carry on with the usual dose. Store tablets and capsules at room temperature, dry and out of reach of children. If you have surgery or a dental procedure planned, tell the doctor that you take a supplement with vitamin K, especially if you also use medicines that affect the blood.
If you take a D3 + K2 tablet and another vitamin D product, add up the vitamin D from both. The K2 does not change the vitamin D upper level.
Vegan options and combinations
The OstroVit VEGE range uses vitamin D3 from Icelandic lichen and MK-7, in a plant capsule or a tablet, so the D3 needs no animal-derived ingredient. Other products add calcium, or vitamin C and zinc, to the same dose. Check the calcium amount if you also take a calcium supplement. The vitamin C and zinc capsule is not for people prone to kidney stones.
How to choose a D3 + K2 product
- Read the vitamin K line and its % NRV. 50 to 100 µg is the range on our labels.
- Check the vitamin D dose. 2000 IU (50 µg) is the common adult strength, and 4000 IU is labelled for people over 75.
- Look for "MK-7" or "menaquinone-7" in the ingredient list.
- Pick a format: tablet, capsule, or a plant-based capsule if you avoid animal ingredients.
- Count other supplements with vitamin D, vitamin K or calcium, and add them together.
- If you take any anticoagulant, ask your doctor first.
Price per day is the pack price divided by the number of days it lasts. A 90-tablet pack taken once a day lasts 90 days. A 100-tablet pack of the VEGE tablets, taken as a half tablet, lasts 200 days.
What EU law lets us say about vitamin K
Regulation (EU) No 432/2012 authorises two claims for vitamin K, for products that provide at least 15% of the NRV per daily dose, whatever the form:
- Vitamin K contributes to normal blood clotting.
- Vitamin K contributes to the maintenance of normal bones.
No authorised claim mentions K2 separately or combines vitamins D and K. Our D3 + K2 products carry the vitamin D and vitamin K claims above, each on its own. Browse the full vitamin D range to see which ones include K2.
FAQ
What is vitamin K2 and what does it do?
It is the menaquinone group of vitamin K. The authorised EU claims say vitamin K contributes to normal blood clotting and to the maintenance of normal bones.
Does vitamin K thin the blood?
No, the opposite. Vitamin K contributes to normal blood clotting. Warfarin and similar medicines work by blocking vitamin K, which is why a supplement can interfere with them and why any change needs a doctor.
Should I take K2 together with D3?
You do not have to. They can be taken in one tablet or separately. Combined products are convenient, and the choice depends on the doses you want, not on an extra approved effect.
MK-4 or MK-7: which is better?
MK-7 is the more common supplement form and stays in the blood longer. No EU claim ranks one above the other. Choose by label dose, format and your doctor's advice.
How many micrograms of K2 do I need?
The NRV is 75 µg and EFSA's adequate intake for adults is 70 µg a day, from food and supplements together. Products in our range give 50 to 100 µg per daily dose.
Can I take K2 every day?
At the label dose, daily use is how these products are meant to be taken, unless you use an anticoagulant, are pregnant or breastfeeding, or your doctor has advised otherwise.
Sources
- Regulation (EU) No 432/2012, authorised health claims
- EFSA: Dietary reference values for vitamin K (2017)
- EFSA: Scientific opinion on the tolerable upper intake level of vitamin D (2012)
- NIH Office of Dietary Supplements: Vitamin K fact sheet for health professionals
Content reviewed by Inese Kalniņa, dietitian.
