High Quality Vitamin D + K Supplements

Vitamin D increases calcium absorption from the gut. K2 activates osteocalcin (which puts calcium in bones) and matrix Gla protein (which keeps calcium out of arteries). Together they support bone density without raising arterial calcification risk.

MK-7 is preferred over MK-4 for most people because it has a much longer half-life (3 days vs hours) and provides steady effects from a single daily dose. MK-4 needs to be taken multiple times per day at higher doses to be effective.

Common formulas: 1,000–5,000 IU D3 + 90–180 mcg MK-7. Adjust D dose to maintain 25-OH-D in the 40–60 ng/mL range. Take with a fatty meal for absorption. People on warfarin should consult a clinician — K2 can affect blood thinning.

If you have any cardiovascular risk factors, calcium concerns, or are taking calcium supplements, D3+K2 is preferable. K2 redirects calcium away from arteries and into bones. D3 alone is fine if you're young, healthy, and have no calcium imbalance concerns.

Talk to your clinician first. K2 can affect warfarin dosing because vitamin K is the antidote to warfarin. Newer anticoagulants (DOACs like apixaban, rivaroxaban) don't interact with vitamin K. Consistency in K intake matters more than avoidance.

Natto (fermented soybeans) is by far the highest source. Other sources: hard cheeses, egg yolks, butter from grass-fed cows, and fermented foods. Most Western diets are low in K2 — supplementation is one of the simplest ways to ensure adequate intake.

Some evidence suggests K2 (180 mcg MK-7 daily) may slow or modestly improve arterial calcification over 1–3 years. Effects build slowly. Pair with optimized vitamin D, magnesium, and lifestyle factors for best results.

Generally well-tolerated. Rare reactions include digestive upset or skin reactions. Excess vitamin D is the main risk (toxicity from doses above 40,000 IU sustained), not K2. Test 25-OH-D periodically when on higher D doses.

With a meal containing fat — both are fat-soluble. Many people take it with breakfast or lunch. K2 has a half-life of 3 days (MK-7), so once-daily dosing maintains steady levels.