Vitamin D3 and K2: is there a correct ratio?

The short answer: no. No authority has ever set a ratio of vitamin D3 to vitamin K2 — not the EFSA, not the German Federal Institute for Risk Assessment (BfR), not the German Nutrition Society. The two rules of thumb circulating online differ by a factor of ten: sometimes it is 100 µg of K2 per 1,000 IU of vitamin D3, sometimes 10 µg. They cannot both be right, and neither can be traced back to a source.

For a purchase decision that is a noticeable difference. Anyone laying two combination products side by side and working out which one comes closer to “100 per 1,000” is choosing by a criterion that does not exist — and is missing the number that does appear in the official reference values: the amount of vitamin K that adds up over a day.

The calculation in question

The ratio is quickly worked out: the micrograms of K2 on the label divided by the amount of vitamin D in thousands of International Units. For vitamin D the conversion is fixed at 40 IU = 1 µg. A tablet with 4,000 IU and 200 µg of K2 therefore comes to 50 µg of K2 per 1,000 IU.

Across our range it looks like this:

Product	per tablet/capsule	K2 per 1,000 IU of D3
Vitamin D3 4,000 IU + K2 200 µg – 365 tablets	100 µg D3 (4,000 IU), 200 µg K2	50 µg
Liposomal D3 5,000 IU + K2 100 µg – 180 capsules	125 µg D3 (5,000 IU), 100 µg K2	20 µg
Vitamin D3 10,000 IU + K2 200 µg – 180 tablets	250 µg D3 (10,000 IU), 200 µg K2	20 µg
Vitamin D3 20,000 IU + K2 200 µg – 360 tablets	500 µg D3 (20,000 IU), 200 µg K2	10 µg

Four products from the same manufacturer, a spread of 10 to 50 µg per 1,000 IU — and that is not carelessness but the consequence of the K2 amount not being tied to the D3 amount. All four contain 100 or 200 µg of MK-7 per unit; what differs between them is the vitamin D strength.

Important for the comparison: the ratio is a property of the tablet and does not change with the intake rhythm. Both nutrients sit in the same pressed body, so they share every dilution. What the rhythm does change is the amount that arrives per day — and the authorities' reference values speak about exactly that amount:

Product	rhythm per the label	D3 per day	K2 per day
4,000 IU + K2 200 µg	daily	100 µg (4,000 IU)	200 µg
4,000 IU + K2 200 µg	every 2nd day	50 µg (2,000 IU)	100 µg
Liposomal 5,000 IU + K2 100 µg	every 5 days	25 µg (1,000 IU)	20 µg
10,000 IU + K2 200 µg	every 10 days	25 µg (1,000 IU)	20 µg
20,000 IU + K2 200 µg	every 20 days	25 µg (1,000 IU)	10 µg

Between the first and the last row there is a factor of twenty in vitamin K — but only a factor of five in the ratio. Anyone choosing by the ratio is therefore precisely not seeing the bigger difference. How the vitamin D strengths compare with one another is worked through in Vitamin D3 K2 20,000 IU compared.

Where the rules of thumb come from

The figure of 100 µg does have a real background — just not as a ratio. It appears in research on menaquinone-7 as an absolute daily amount. The longest study of this kind is a three-year, placebo-controlled trial by Knapen and colleagues (Osteoporosis International, 2013) in 244 healthy postmenopausal women; they received 180 µg of MK-7 per day, and vitamin K status improved, measured by the ratio of uncarboxylated to carboxylated osteocalcin. Vitamin D was not scaled along with it in that dosing — the amount stood on its own.

The BfR also cites absolute figures: in studies with MK-7 of up to around 400 µg per day no adverse health effects were observed, and at 100 µg of MK-7 per daily dose the BfR sees no indication of health impairment in adults — provided the pack carries a warning for people taking anticoagulants. For its maximum-level proposal for food supplements the BfR sets 25 µg of vitamin K2 or 80 µg of vitamin K1 per recommended daily portion.

Where the coupling of that amount to “per 1,000 IU of vitamin D3” arose cannot be traced cleanly. It appears in consumer guides and product descriptions, not in a guideline, a regulation or a study. The smaller variant — 10 µg per 1,000 IU — describes what depot products contain anyway rather than a rule they are following: 200 µg of K2 on a 20,000 IU tablet gives exactly that value.

Why a ratio is the wrong form for this question

All reference values for vitamin K are formulated in absolute terms; none stands in relation to vitamin D:

Reference value	Vitamin K	Origin
Nutrient reference value (NRV)	75 µg	Regulation (EU) No 1169/2011, Annex XIII — the basis for the percentage figure on the label
Adequate intake	70 µg/day for adults	EFSA, Dietary Reference Values for vitamin K (2017) — for vitamin K as a whole; a separate value for K2 does not exist
Reference value	60–80 µg/day depending on age and sex	German Nutrition Society (DGE)
Maximum-level proposal for food supplements	80 µg K1 or 25 µg K2 per daily portion	BfR — a proposal, not applicable law
Tolerable upper intake level	none derived	EFSA — the data are not sufficient for one

Setting the best-known rule of thumb against these values shows why the form does not hold. At 4,000 IU of vitamin D daily, “100 µg per 1,000 IU” arithmetically calls for 400 µg of K2 per day — more than five times the adequate intake and more than twice the amount given in the three-year MK-7 trial. At 1,000 IU daily the same rule calls for 100 µg. The person has stayed the same, and so has their vitamin K requirement; the only thing that has changed is the vitamin D tablet in their hand.

Then there is the substantive finding. The BfR examined the interaction of the two vitamins explicitly in 2023 and states in opinion 065/2023 that it is unclear to what extent it has a positive effect on health; there are not enough data for a reliable risk assessment, and studies with combined administration are so far few. From a body of data that is insufficient for an assessment, no conversion rule can be derived.

What may appear on the tin

Authorised health claims are listed in Regulation (EU) No 432/2012. For these two vitamins they are the following sentences, and they may only be used in this wording:

• Vitamin D contributes to normal absorption and utilisation of calcium.
• Vitamin D contributes to the maintenance of normal bones.
• Vitamin D contributes to the normal function of the immune system.
• Vitamin D contributes to the maintenance of normal muscle function.
• Vitamin K contributes to the maintenance of normal bones.
• Vitamin K contributes to normal blood clotting.

None of these statements mentions a combination, a ratio or a minimum amount of the other vitamin. A product may carry a claim as soon as it contains at least 15 % of the nutrient reference value per daily portion — for vitamin K that is 11.25 µg. That is the only quantity-related condition the law knows.

Food supplements are not a substitute for a balanced and varied diet and a healthy lifestyle.

What the menu already contributes

With vitamin K the supply question looks different than with vitamin D, and that is the real reason a ratio misleads. Vitamin K1 (phylloquinone) is found in green leafy vegetables and brassicas — kale, chard, spinach, Brussels sprouts, broccoli. Vitamin K2 (menaquinones) occurs in fermented and animal foods, in particularly high amounts in Japanese natto. The adequate intake of 70 µg per day refers to vitamin K as a whole; a portion of green vegetables generally covers it.

Vitamin D, by contrast, is barely supplied by food: the consumption surveys cited by the BfR arrive at about 2 to 4 µg per day, which is why the DGE sets an estimated value of 20 µg for the case where the body forms none of its own. The gap a supplement closes is therefore of a different size for the two vitamins — which on its own argues against thinking of them in a fixed numerical ratio.

When the K2 amount really does matter

There is one group for whom the absolute amount is not an academic question: anyone taking coumarin-type anticoagulants — such as phenprocoumon or warfarin — should use vitamin K-containing products only after consulting a doctor. Vitamin K can weaken the therapeutic effect of these medicines, K1 as well as K2; the BfR points out explicitly that many older people in Germany take such medication. What matters here is the amount of vitamin K per day and its consistency, not its ratio to anything.

Anyone in that group who still wants to supplement vitamin D gets along more easily with a pure D3 product such as Vitamin D3 4,000 IU without K2: one variable fewer. How much vitamin K is unproblematic at the upper end is covered in Vitamin K2 overdose.

Frequently asked questions

Is a product with more K2 per 1,000 IU the better one?

That cannot be derived from the available data. There is no reference value against which a ratio could be checked, and the BfR describes the data on combined administration as insufficient for an assessment. What can sensibly be compared instead are the two absolute daily amounts — vitamin D against the EFSA upper level of 100 µg per day, vitamin K against the adequate intake of 70 µg per day.

Do I have to buy K2 separately if my D3 product does not contain any?

There is no authorised claim for that, and in the BfR's assessment no evidence either that vitamin K2 safeguards a vitamin D intake. A pure D3 product is not a compromise. Whether additional vitamin K makes sense depends on the menu, not on the D3 dose.

Does the ratio change if I take the tablet less often?

No. Both vitamins sit in the same tablet, and a longer interval dilutes them equally. What changes is the daily amount of both nutrients — with the 20,000 IU tablet on a twenty-day rhythm that is 25 µg of vitamin D and 10 µg of K2.

Which number should I look at instead?

The recommended intake on the back of the pack. Strength divided by the interval gives the daily amount, and only that can be held against the reference values. On timing and the role of fat at intake, the practical side is in Taking vitamin D3 K2 5,000 IU correctly.

Sources: Regulation (EU) No 432/2012 (list of authorised health claims); Regulation (EU) No 1169/2011, Annex XIII (nutrient reference values); BfR, opinion 065/2023 of 7 December 2023; 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 K and vitamin D; Knapen MHJ et al., “Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women”, Osteoporosis International 24(9), 2013 (PubMed 23525894).