Vitamin K2 and Vitamin D: How Much K2?

Quick answer

There is no official amount of vitamin K2 to take with vitamin D. The adequate intake for all forms of vitamin K is 90 mcg a day for women and 120 mcg for men, and the three-year bone trial of MK-7 used 180 mcg a day. Anyone taking warfarin must not start K2 without their doctor.^1,2,3

Key facts

Vitamin D's active form tells the gut to absorb calcium, and vitamin K is needed to finish osteocalcin, a protein in bone.^1,4
A 2020 pooled analysis of 8 trials with 971 people found higher total bone mineral density when vitamin K and vitamin D were given together than in the comparison groups.⁵
No upper limit is set for vitamin K. Vitamin D's adult limit is 100 mcg (4,000 IU) a day from all sources.^1,6
In healthy volunteers on a warfarin-like medicine, as little as 10 to 20 mcg of MK-7 a day shifted clotting tests in some of them.⁷

Why the two are sold together

The pairing comes from where each vitamin acts on calcium. Vitamin D works at the start: its active form tells the gut to absorb calcium and phosphate. Vitamin K works on proteins that handle calcium afterwards. It is the helper for an enzyme that finishes osteocalcin, a protein in bone, and matrix Gla protein, found in blood vessel walls, bone and cartilage.^1,4

Vitamin K is sold alone or combined with a few other nutrients, most often calcium, magnesium or vitamin D.^1,3

Whether the two compete on the way in has only been studied in the laboratory. In mouse intestine and in human gut cells grown in a dish, vitamins D, E and K competed with one another for uptake. No study in our sources has tested this in people taking ordinary amounts.⁸

What the evidence shows for each, and for both

The three statements below are quoted from our ingredient pages with their grades. The trials of the pair follow them.

Helps the body absorb calcium and maintain normal bones*^4,9,10

Moderate evidence

This is vitamin D's best-established role and the basis of official intake recommendations. It matters most when intake and sun exposure are low. In adults who mostly had adequate levels already, extra vitamin D gave no added benefit for bones: VITAL tested 2,000 IU a day in 25,871 people for about five years and found no difference from placebo.

Amount studied: The recommended 15 to 20 mcg (600 to 800 IU) a day from all sources; VITAL tested 2,000 IU a day on top of diet

Contributes to the maintenance of normal bones*^1,11

Moderate evidence

Vitamin K is needed to activate osteocalcin, a protein in bone, and NIH reports that the European Food Safety Authority found a cause and effect relationship between dietary vitamin K and the maintenance of normal bone. Supplements beyond a normal intake are another matter: trials are mixed, a 2019 review of 36 randomized trials found no clear effect on bone mineral density in women after menopause once lower quality trials were set aside, and the FDA has not authorized a health claim for vitamin K in the US.

Amount studied: Adequate intake of 90 to 120 mcg a day from food; supplement trials used from 180 mcg of MK-7 to 45 mg of MK-4 a day

MK-7 may help maintain bone mineral density in women after menopause*^1,2,11

Early evidence

One three-year randomized trial in 244 healthy women after menopause found that 180 mcg of MK-7 a day slowed the usual decline in bone mineral content and density at the lower spine and the femoral neck, though not at the total hip, and bone strength measures held up better than on placebo. It came from a single vitamin K research group, and other trials of vitamin K have found no effect on bone density, so the evidence is early.

Amount studied: 180 mcg of MK-7 a day for three years

A 2020 pooled analysis looked at the pair directly: 8 randomized trials with 971 people, comparing vitamin K plus vitamin D with control groups. Total bone mineral density came out higher with the pair, and inactive osteocalcin came out lower, a sign that more of it had been finished by vitamin K. In the subgroup that used less than 500 mcg a day of K2 or unspecified vitamin K, the comparison groups ate their normal diet or took nothing, so those results cannot show what vitamin K added beyond vitamin D.^1,5

When vitamin D or calcium is given alongside vitamin K in a trial, it can be hard to tell which nutrient made any difference to bone, which may explain some of the mixed results.¹

In a 12-month trial of 381 women after menopause, 1 mg of K1 or 45 mg of MK-4 a day activated more osteocalcin than placebo but made no difference to bone mineral density at the spine or hip. Every woman in the trial also took calcium and 400 IU of vitamin D3.¹

How much vitamin K2 to take with vitamin D

There is no separate recommended amount for vitamin K2. The adequate intake covers all forms of vitamin K, and it was set from what healthy people eat, because there was not enough evidence to work out a precise requirement.¹

Amounts named in the sources, per day^1,2,6,12
What	Amount
Vitamin K adequate intake, women	90 mcg, all forms together
Vitamin K adequate intake, men	120 mcg, all forms together
MK-7 in the three-year bone trial	180 mcg
Vitamin D recommended, adults 19 to 70	15 mcg (600 IU)
Vitamin D in the VITAL and DO-HEALTH trials	50 mcg (2,000 IU)
Upper limit, vitamin D	100 mcg (4,000 IU) from all sources
Upper limit, vitamin K	None set

No source we read sets a ratio of K2 to vitamin D, so the ratio in a combination product is the maker's choice rather than an official figure. Labels can also mix units: vitamin D is often printed in IU as well as mcg, while vitamin K is printed in mcg.^1,4

For vitamin D, 1 mcg equals 40 IU. So 10 mcg is 400 IU, 15 mcg is 600 IU, 50 mcg is 2,000 IU and 100 mcg is 4,000 IU.⁴

MK-7 stays in the blood far longer than K1, so its levels are steadier and build up 7 to 8 fold with daily use.^1,13

Taking them with food

Vitamin K is absorbed the way dietary fat is, with the help of bile and digestive enzymes. Eating vegetables with some fat increases how much of their vitamin K the body takes up.¹

In 17 people seen at a bone clinic whose blood levels had stayed low on supplements, switching the same dose to the largest meal of the day raised their levels by about 57% on average over 2 to 3 months. The study had no comparison group.¹⁴

Since both are fat soluble, one meal with some fat serves both. Supplements of K1 and of MK-7 reach their highest blood level about 4 hours after a dose, and MK-7 then stays in the blood much longer than K1.¹³

What's in ours

What’s in ours

Vitamin D3: Vitamin D-3, 50 mcg (2,000 IU) per serving, from the label
Men's Multi: Vitamin D, 10 mcg per serving, from the label
Ashwagandha Complex: Vitamin D3, 20 mcg per serving, from the label
Immune Support: Vitamin D3, 40 mcg per serving, from the label

None of our products contains vitamin K, and our Vitamin D3 softgel has no K2 in it.

Warfarin and other cautions

Ask your pharmacist or doctor first

Warfarin and similar blood thinners work by blocking vitamin K. A sudden rise in vitamin K from food or supplements can weaken their effect and raise the chance of a blood clot, and a sudden drop can strengthen it and cause dangerous bleeding. NIH and the warfarin label advise keeping vitamin K intake about the same from day to day. NIH names warfarin and similar medicines used in Europe (phenprocoumon, acenocoumarol and tioclomarol), not blood thinners that work in other ways.^1,3,15,16

On the medicine's label

In 18 healthy volunteers kept on acenocoumarol, a blood thinner that works like warfarin, MK-7 at 45 mcg a day lowered the INR by about 40%, and 10 or 20 mcg a day lowered it enough to matter in at least 40% and 60% of them. The researchers concluded that people on these medicines should avoid MK-7 supplements.⁷

This is why a D3 and K2 product is not just a vitamin D product. Vitamin K supplements vary widely, some providing 4,050 mcg, far above the 10 to 20 mcg of MK-7 that shifted clotting tests in that study.^1,7

Ask first if you take any other blood thinner, such as apixaban, rivaroxaban, clopidogrel or daily aspirin, or if you have had a blood clot or have a bleeding or clotting disorder.
Ask first if you take a thiazide water pill, a statin, steroid tablets, orlistat or a bile acid sequestrant: each affects vitamin D, and the last two lower vitamin K absorption too.^3,6
Ask first if you have high blood calcium, kidney disease or kidney stones, or an overactive parathyroid gland.
Ask first if you are pregnant or nursing, or want to give either vitamin to a child.

Questions people ask

Do you need K2 if you take vitamin D?

Not as a rule. NIH says most American diets provide enough vitamin K, and the large vitamin D trials of 2,000 IU a day gave no K2. The pooled analysis of the pair found higher bone density than in comparison groups, but it did not test whether vitamin D works less well without K2.^3,5,12

Is K2 better than K1 to take with vitamin D?

MK-7, a form of K2, stays in the blood far longer than K1 and activated more osteocalcin in a head-to-head study. The authors of the pooled analysis expected a larger effect with K2, but no trial in our sources compared K1 and K2 with vitamin D directly.^5,13

Can you take vitamin D and K2 while on warfarin?

Not without your doctor. Warfarin works by blocking vitamin K, so starting, stopping or changing a K2 supplement, or a multivitamin that contains it, can change how well the medicine works. NIH and the warfarin label both advise keeping vitamin K intake steady.^3,15

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.