Vitamin D3 with K2: what is proven and what isn't
Futures Nutrition Editorial Team · 11 August 2026
Vitamin D3 with K2: what is proven and what isn't
The short answer first: the two vitamins sit together on the tub because they share one authorised claim — the one about bones. The reasoning you read far more often in advertising, namely that K2 redirects calcium out of the arteries and into the bones, is not an authorised claim, and in the assessment of the German Federal Institute for Risk Assessment (BfR) it is not scientifically established either.
That difference matters when you buy. If you believe K2 is the necessary safeguard for taking vitamin D, a plain D3 product will leave you uneasy — and there is no solid basis for that unease. If you know which two sentences the EU permits for vitamin K at all, you can judge a combination product for what it is: two nutrients in one tablet, not a safety package.
What a D3-K2 tub is allowed to say
Authorised health claims are listed in Regulation (EU) No 432/2012. It is a closed list: whatever is not on it, a label may not assert. For these two vitamins, the sentences are:
| Nutrient | Authorised claim (wording) |
|---|---|
| Vitamin D | Vitamin D contributes to normal absorption and utilisation of calcium |
| Vitamin D | Vitamin D contributes to the maintenance of normal bones |
| Vitamin D | Vitamin D contributes to the normal function of the immune system |
| Vitamin D | Vitamin D contributes to the maintenance of normal muscle function |
| Vitamin K | Vitamin K contributes to the maintenance of normal bones |
| Vitamin K | Vitamin K contributes to normal blood clotting |
The overlap is exactly one line: both contribute to the maintenance of normal bones. That is the factual core of the combination — two nutrients addressing the same subject, in one tablet. No more, but no less either.
A claim may only be carried if the product contains the nutrient in a meaningful amount: at least 15 % of the nutrient reference value per daily portion. The reference values are in Annex XIII of Regulation (EU) No 1169/2011 and stand at 5 µg for vitamin D and 75 µg for vitamin K — so the threshold is 0.75 µg and 11.25 µg per daily portion respectively. Ordinary combination products clear it easily, which is why the mere presence of the claim on the packaging says nothing about how high the dose is.
The explanation that always comes along with it
The story runs like this: vitamin D increases calcium absorption from the gut, and vitamin K is said to ensure that this calcium ends up in bone rather than in the artery wall. The biochemical starting point is real. Vitamin K acts as a cofactor of gamma-glutamyl carboxylase and is thereby involved in the carboxylation of vitamin K-dependent proteins; the BfR names three processes in which such proteins play a role: blood clotting, bone metabolism and vascular biology. Those proteins include osteocalcin in bone and matrix Gla protein in the vessel walls.
A plausible mechanism, however, does not amount to a demonstrated benefit. In 2023 the BfR examined precisely this question and writes verbatim in its opinion 065/2023 (translated from the German original): "The claim that vitamin K2 prevents the risk of vascular calcification caused by high vitamin D intakes has to date not been scientifically established." And further: the extent to which the interaction of the two vitamins has a positive effect on health is currently unclear; there are not enough data for a reliable risk assessment. Studies in which vitamin K and vitamin D were given together are so far few.
The EU list fits that picture: no claim relating to the heart or blood vessels is included for vitamin K. EFSA assessed a corresponding application for vitamin K2 (scientific opinion of 2012 on ID 125) — it was not added to the list of authorised claims. What remains permitted are the two sentences in the table above.
For the purchasing decision this means: K2 in the product is not an antidote, it is a second nutrient. How high the vitamin D amount in such a tablet may be, and when it becomes critical, is a separate question — it is answered in Can you take too much vitamin D?.
Where vitamin K comes from in everyday food
Vitamin K is an umbrella term for two groups of substances. Vitamin K1 (phylloquinone) is found above all in green leafy vegetables and brassicas; vitamin K2 (menaquinones, MK-n) occurs in animal and fermented foods — meat, cheese, eggs, and in particularly high amounts in Japanese natto made from fermented soybeans. In 2017 EFSA derived an adequate intake of 70 µg of vitamin K per day for adults, and did so for vitamin K as a whole: there is no separate reference value for K2, because the data are not sufficient for one.
That is why the supply question sits differently for vitamin K than for vitamin D. Vitamin D barely occurs in food — average dietary intake is around 2 to 4 µg per day according to the consumption surveys cited by the BfR, which is why the German Nutrition Society (DGE) sets an estimated value of 20 µg for the case where the body's own production is absent. Vitamin K, by contrast, is as a rule supplied in sufficient amounts by a normal diet that includes leafy vegetables. A combination product therefore closes a gap here less often than the packaging suggests.
What is actually in the combination products
The decisive column is not the number on the front, but the amount per day that follows from the strength and the intake rhythm:
| Product | per tablet/capsule | rhythm on the label | calculated per day |
|---|---|---|---|
| Vitamin D3 4,000 IU + K2 200 µg – 365 tablets | 100 µg D3, 200 µg K2 | daily or every second day | 100 or 50 µg D3, 200 or 100 µg K2 |
| Liposomal D3 5,000 IU + K2 100 µg – 180 capsules | 125 µg D3, 100 µg K2 | every 5 days | 25 µg D3, 20 µg K2 |
| Vitamin D3 10,000 IU + K2 – 360 tablets | 250 µg D3, 200 µg K2 | every 10 days | 25 µg D3, 20 µg K2 |
| Vitamin D3 20,000 IU + K2 200 µg – 360 tablets | 500 µg D3, 200 µg K2 | every 20 days | 25 µg D3, 10 µg K2 |
For context, the reference figures that belong with this: EFSA derived a tolerable upper intake level (UL) for vitamin D of 100 µg per day for adults — the amount from all sources that can be taken long term without expected adverse effects. For food supplements the BfR proposes lower maximum amounts per recommended daily portion: 20 µg vitamin D, 80 µg vitamin K1 and 25 µg vitamin K2. There is no UL for vitamin K; in studies of MK-7 intakes up to roughly 400 µg per day no adverse health effects were observed, and the BfR sees no indication of health impairment at 100 µg MK-7 per daily dose in adults — provided the packaging carries a warning for people on anticoagulants.
The first row stands out: the product with the smallest number on the tub delivers by far the highest daily amount — 100 µg vitamin D and 200 µg K2 when taken daily. Anyone who keeps to the depot rhythms of the stronger variants lands at 25 µg vitamin D and 10 to 20 µg K2 per day. Why the big numbers are not big daily amounts is worked through in detail in Vitamin D3 K2 20,000 IU: the high dose compared.
When K2 in the product matters — and when it gets in the way
There is one group for whom the combination is not a matter of preference: anyone taking coumarin-type anticoagulants (such as phenprocoumon or warfarin) should use vitamin K-containing products only after speaking to a doctor. Vitamin K — both K1 and K2 — can weaken the therapeutic effect of these medicines; the BfR points out explicitly that many older people in Germany take them. In that case a plain D3 product such as Vitamin D3 4,000 IU without K2 is the simpler choice.
For everyone else it is an arithmetic question. Two nutrients in one tablet are convenient and usually cheaper than two tubs — whether that holds in a specific case only the price per day shows, which Buying vitamin D3 + K2: label, price, supply works out. If you eat plenty of leafy vegetables you cover vitamin K anyway and gain little from K2. And if you want to know how much vitamin K is unobjectionable at the upper end, the figures are in Vitamin K2 overdose.
Frequently asked questions
Do I have to take K2 if I take vitamin D?
No. There is no authorised claim and, in the BfR's assessment, no scientific evidence either that vitamin K2 safeguards a vitamin D intake. Plain D3 products are not a compromise.
Does vitamin D use up the body's vitamin K?
This phrasing appears frequently but has no firm basis in the authorities' reference values. The BfR expressly describes the interaction of the two vitamins as unclear and the data as insufficient for an assessment.
K1 or K2 — does the difference matter?
Not for the authorised claims: they apply to vitamin K regardless of the form. The differences lie in pharmacokinetics. According to the data compiled by the BfR, MK-7 has a half-life of about three days and vitamin K1 only one to two hours — which is why depot products mostly contain MK-7.
When is the right time to take it?
Both vitamins are fat-soluble and are therefore taken with a meal containing some fat. What that means in practice is set out in Taking vitamin D3 K2 5000 IU correctly: a guide.
Food supplements are not a substitute for a balanced and varied diet and a healthy lifestyle.
Sources: Regulation (EU) No 432/2012 (list of permitted health claims); Regulation (EU) No 1169/2011, Annex XIII (nutrient reference values); BfR, opinion 065/2023 of 7 December 2023 "Hochdosierte Nahrungsergänzungsmittel mit Vitamin D können langfristig die Gesundheit beeinträchtigen"; BfR, updated maximum level proposals for vitamins and minerals in food supplements (2021); EFSA, Dietary Reference Values for vitamin K (2017) and for vitamin D (2016); DGE reference values for vitamin D.
