Most vitamin K2 supplements sold for general health contain between 100 and 200 mcg of the MK-7 form, and that range is where most of the research on heart and bone benefits clusters. But the honest answer is more nuanced than a single number, because no major health authority has set a specific recommended daily intake for K2 alone, and the right dose depends on which form of K2 you’re taking.
Why There’s No Official K2 Number
The NIH sets an Adequate Intake for total vitamin K: 120 mcg per day for adult men and 90 mcg per day for adult women. That figure covers all forms of vitamin K combined, including K1 (found in leafy greens) and the various subtypes of K2. It was established based on intake levels observed in healthy populations, not on dose-response trials for K2 specifically. The NIH notes that “no data on normal ranges of menaquinones are available,” meaning scientists don’t yet have enough information to carve out a separate target for K2.
Most people get their total vitamin K primarily from K1 in vegetables like spinach, kale, and broccoli. K2 shows up in smaller amounts in animal-based and fermented foods. So the official Adequate Intake is largely a reflection of K1 consumption, and it tells you relatively little about how much supplemental K2 you might benefit from.
MK-7 vs. MK-4: Two Very Different Doses
Vitamin K2 isn’t one compound. It’s a family of molecules labeled MK-4 through MK-13, based on their chemical structure. The two forms you’ll find in supplements are MK-4 and MK-7, and they behave differently in the body.
MK-7, the form found in fermented foods like natto, stays in your bloodstream much longer than MK-4. That longer half-life means a small daily dose can maintain steady blood levels. Most clinical trials and consumer supplements use MK-7 in the range of 100 to 200 mcg per day. For context, a single 50-gram serving of natto (a traditional Japanese fermented soybean dish) delivers roughly 380 mcg of MK-7, so supplement doses in that range are well within what people consume through food in some cultures.
MK-4 is a different story. Your body clears it from the bloodstream quickly, so achieving a meaningful effect requires dramatically higher doses. In Japanese clinical settings, MK-4 has been used at 45 mg per day (that’s 45,000 mcg) for bone health in postmenopausal women with osteoporosis. A 2020 study in women with osteoporotic fractures found that even 5 mg per day of MK-4 was enough to normalize a key marker of bone protein activation. These are therapeutic doses prescribed under medical supervision, not general wellness recommendations.
What the Research Shows for Heart Health
One of the main reasons people supplement K2 is to keep calcium out of their arteries and in their bones. K2 activates proteins that direct calcium to the right places in the body. Without enough K2, those proteins remain inactive, and calcium can accumulate in blood vessel walls instead of bone tissue.
A large randomized controlled trial of 389 men with coronary artery disease tested 720 mcg per day of K2 (combined with vitamin D) against a placebo over two years. In participants who already had significant arterial calcification (calcium scores of 400 or above), the supplement group saw meaningfully slower calcification progression compared to placebo. In those with less severe disease, the difference wasn’t statistically significant. This suggests higher doses of K2 may matter most for people who already have calcification underway, though 720 mcg is well above what most consumer supplements provide.
A Practical Range for Most People
If you’re taking K2 for general bone and cardiovascular support, 100 to 200 mcg of MK-7 per day is the most commonly used and studied range. Some practitioners recommend doses up to 300 mcg for people with specific risk factors like low bone density or a family history of arterial calcification. The research on higher doses (700+ mcg) is still limited to specific clinical populations.
Because K2 is fat-soluble, taking it with a meal that contains some fat improves absorption. Many people pair it with vitamin D3, and you’ll find plenty of combination supplements on the market. The rationale is that vitamin D increases calcium absorption from food, while K2 helps direct that calcium into bones rather than soft tissues. A 2020 review in the journal Nutrients supported this theory, finding that vitamin K helps prevent vascular calcification from progressing. There’s no established ideal ratio of D3 to K2, but the combination is considered complementary.
No Known Toxicity Threshold
Unlike vitamins A and D, vitamin K2 has no established upper tolerable intake level. Health authorities haven’t set one because no toxicity has been documented at any studied dose, including the 45 mg doses used in Japanese osteoporosis treatment. That said, the absence of a known ceiling doesn’t mean more is always better. It simply means the safety profile is wide.
The one major exception involves blood-thinning medications like warfarin. These drugs work by blocking vitamin K’s role in blood clotting, so adding K2 (or K1) can directly interfere with their effectiveness. Even amounts as small as 25 mcg of vitamin K have been documented to shift blood clotting levels in people on warfarin. If you take any anticoagulant medication, K2 supplementation needs to be coordinated with whoever manages your dosing.
Getting K2 From Food
Natto is by far the richest dietary source of K2, delivering about 380 mcg of MK-7 per 50-gram serving. If you eat it regularly, you may not need a supplement at all. Other sources include hard cheeses (particularly gouda and brie), egg yolks, chicken liver, and butter from grass-fed animals, though these provide much smaller amounts, mostly as MK-4. Bacteria in your gut also produce some long-chain menaquinones, but how much of that your body actually absorbs and uses remains unclear.
For people who don’t eat fermented foods or animal products regularly, supplementation is the most reliable way to get a consistent daily dose of K2. The MK-7 form at 100 to 200 mcg per day covers the range supported by most current evidence for general health.