Most people supplement vitamin K2 in the range of 100 to 200 mcg per day of the MK-7 form, which is the most common type sold in stores. But the right amount depends on which form you’re taking and what you’re trying to achieve, because K2 dosages in clinical research range from as low as 90 mcg all the way up to 45 mg, a 500-fold difference.
Why There’s No Single Official Number
The NIH sets an Adequate Intake for total vitamin K (both K1 and K2 combined) at 120 mcg per day for adult men and 90 mcg for adult women. That figure is based mostly on vitamin K1 from leafy greens, not K2 specifically. No government agency has established a separate recommended intake for K2 alone, which is why you’ll see such a wide range of doses on supplement labels.
There’s also no established upper limit for vitamin K2. Unlike vitamins A or D, K2 has not shown toxicity at high doses in research. Clinical trials have used up to 45 mg (45,000 mcg) of MK-4 daily for years without reported adverse effects. That said, the absence of a formal ceiling doesn’t mean more is always better.
MK-7 vs. MK-4: Two Very Different Dosing Ranges
Vitamin K2 comes in several forms, but two dominate the supplement market: MK-7 and MK-4. They behave differently in your body, and this changes how much you need to take.
MK-7 has a long half-life, staying active in your bloodstream for days. This means a single daily dose in the microgram range is enough to maintain steady levels. Most supplements contain 100 to 200 mcg of MK-7, and clinical trials have used doses in that range with positive results. A three-year trial in postmenopausal women found that 180 mcg of MK-7 per day improved bone strength and slowed height loss in the spine.
MK-4 is a completely different story. It clears your blood in roughly two hours, so it needs to be taken multiple times a day and at far higher doses. Nearly all of the bone-health trials using MK-4 gave participants 45 mg per day, split into three doses of 15 mg each. In Japan, this 45 mg dose is actually prescribed as a pharmaceutical treatment for osteoporosis. One trial used 15 mg per day. Both dosing levels significantly reduced fracture rates.
If you’re comparing labels, pay attention to units. MK-7 is typically listed in micrograms (mcg), while therapeutic MK-4 doses are in milligrams (mg). One milligram equals 1,000 micrograms, so 45 mg of MK-4 is 250 times larger than 180 mcg of MK-7.
Dosages Used in Heart Health Research
The connection between K2 and cardiovascular health centers on calcium. K2 activates a protein that helps direct calcium into bones and teeth instead of letting it accumulate in artery walls. Observational research has found that people who consume more than about 33 mcg of K2 per day from food have a 57% lower risk of dying from coronary heart disease compared to those eating less than 22 mcg daily.
Clinical trials targeting arterial calcification have used higher doses. A randomized, double-blind trial published in Circulation tested 720 mcg of MK-7 per day (combined with vitamin D) in men with existing aortic valve calcification over two years. That’s roughly four times the typical supplement dose, reflecting the more aggressive approach researchers take when studying people who already have significant calcium buildup in their arteries.
For general cardiovascular maintenance, the 100 to 200 mcg range of MK-7 that most supplements provide aligns with the doses that have shown benefit in other clinical trials, though large-scale heart-specific trials at those lower doses are still limited.
Pairing K2 With Vitamin D
Vitamin D increases how much calcium your body absorbs from food. Vitamin K2 helps ensure that calcium ends up in your bones rather than your soft tissues. This is why the two are frequently sold together and why many practitioners recommend taking them as a pair, especially if you supplement vitamin D at 2,000 IU or more per day.
There’s no formally established ratio of D3 to K2. Common supplement combinations pair 5,000 IU of vitamin D3 with 90 to 200 mcg of MK-7. If you’re taking a high-dose vitamin D supplement on its own, adding K2 separately is a reasonable approach.
How to Get K2 From Food
The richest dietary source of K2 by far is natto, a Japanese fermented soybean dish. A single tablespoon contains about 150 mcg of K2, mostly as MK-7. That one tablespoon essentially covers a full supplemental dose. Other fermented foods contribute much smaller amounts: half a cup of sauerkraut provides roughly 2.75 mcg. Hard cheeses, egg yolks, and dark chicken meat contain K2 as well, but in modest quantities, typically in the MK-4 form.
Most Western diets provide relatively little K2 because the richest sources are either uncommon (natto) or eaten in small portions (cheese, organ meats). This is one reason supplementation is popular.
How to Take It for Best Absorption
Vitamin K2 is fat-soluble, meaning your body absorbs it much more effectively when you take it with a meal that contains some fat. Taking it on an empty stomach or with a fat-free meal can significantly reduce how much actually makes it into your bloodstream. You don’t need a lot of fat: the amount in a handful of nuts, a piece of cheese, or eggs is sufficient.
If you’re using MK-7, once daily with any fat-containing meal works well. If you’re using high-dose MK-4, splitting it across three meals (breakfast, lunch, dinner) compensates for its short time in the body.
One Important Caution: Blood Thinners
If you take warfarin or a similar vitamin K-dependent blood thinner, adding K2 can directly interfere with your medication. Vitamin K is the nutrient warfarin works against, so increasing your intake can reduce the drug’s effectiveness and change your clotting levels unpredictably. Anyone on this type of anticoagulant should talk with their prescriber before starting K2 at any dose. Newer blood thinners that don’t work through the vitamin K pathway are generally not affected.