Vitamin K2 + D3: The Cardiovascular Case, Dosing, and What the Evidence Shows
Vitamin K2 (MK-7 form) directs calcium into bones and away from arterial walls. D3 optimizes calcium absorption. Together they reduce arterial calcification risk. The Rotterdam Study linked high K2 intake to 57% lower cardiovascular mortality. K2 interacts directly with warfarin — physician supervision required for patients on anticoagulation. A 2026 randomised trial, DANCODE, found this combination slowed the buildup of arterial calcium by 21% over two years in people with severe existing calcification — though it did not reduce plaque, and slowing calcium progression has not been shown to reduce heart attacks.
The evidence
Vitamin K2 (MK-7) and D3 work synergistically: D3 is required for calcium absorption from the gut; K2 directs where that calcium goes — into bones rather than arterial walls. Without adequate K2, D3 can paradoxically increase arterial calcification risk by mobilising calcium without directing it correctly.
The Rotterdam Study (4,807 subjects, 10-year follow-up) found the highest-tertile K2 intake was associated with a 57% reduction in cardiovascular mortality.
Vitamin D’s cardiovascular role is narrower than once hoped. Large randomised trials have not shown that vitamin D supplementation lowers coronary calcium or reduces cardiac events, and a 2021 review in the Journal of the American College of Cardiology concluded that its independent cardiovascular benefit remains unproven. Its role in this pairing is to support calcium absorption and correct a measured deficiency — not to prevent heart attacks on its own.
New evidence: the DANCODE trial (2026)
Presented at the European Society of Cardiology Congress in Munich in August 2026 and published in Circulation, DANCODE is the largest randomised test of this idea so far.
Researchers at three Danish hospitals enrolled 398 people with severe coronary calcification — a calcium score of at least 400 Agatston units, with a median of 903. The median age was 71, 30% were women, and 87% were already taking a statin. Half received 720 mcg of vitamin K2 (MK-7) plus 25 mcg (1,000 IU) of vitamin D3 daily; half received a placebo. Neither the participants nor their doctors knew which. Everyone had heart CT scans at the start, at one year, and at two years.
After two years, the supplement group’s calcium score had risen by 196 points, compared with 248 points in the placebo group — a difference of 52 points, or 21% slower buildup. The effect was similar in women and men, and at every level of starting calcium. Blood testing confirmed the supplement was reaching its intended target: inactive matrix Gla protein, the marker of vitamin K insufficiency, fell by about 31%.
What the trial did not show. Calcium scores rose in both groups. This was slower buildup, not reversal or removal. Total plaque volume did not differ between the groups, and neither did soft, non-calcified plaque — the type most closely linked to heart attacks. There were too few cardiac events (2 versus 3) to draw any conclusion from them.
How to weigh it. A calcium score is one of the strongest predictors we have of future cardiac events. What has not been established is that slowing its rise with treatment leads to fewer heart attacks — progression has not been validated as a stand-in for clinical outcomes. The trial’s own authors write that their findings “do not establish a role for routine vitamin K2 and D3 supplementation” for prevention. The accompanying editorial in Circulation goes further, concluding that K2 and D3 “should not be prioritized or substituted for preventive interventions that have a proven beneficial effect on cardiovascular outcomes” — and notes that dense calcium can mark a more stable plaque, which is one reason less calcium is not automatically better.
The trial was investigator-initiated, but financial support and the study tablets came from Kappa Bioscience, a manufacturer of vitamin K2. The company had no role in the trial’s design, analysis, or the decision to publish.
Who this does not apply to. The trial excluded anyone taking warfarin, anyone with a previous stent or bypass, and anyone with a history of blood clots or a clotting disorder.
A second 2026 randomised trial, VitaK-CAC, tested vitamin K2 on its own in people with milder calcification (scores of 50–400) and also found slower calcium progression, with a smaller difference of 22 points over two years. The two trials point the same direction. Neither measured whether people lived longer or had fewer heart attacks.
Reading the label: mcg vs IU
Research papers and supplement labels often use different units, and that trips people up. Two facts clear up most of the confusion.
Vitamin D is measured two ways. Micrograms (mcg) and International Units (IU) describe the same thing in different scales: one microgram equals 40 IU. So when a study reports 25 mcg of vitamin D3, that is exactly the 1,000 IU you would read on a bottle.
Vitamin K2 has no IU value at all. It is only ever measured in micrograms. If you are hunting for an IU number for K2 on your label, you will not find one — it does not exist for this vitamin.
DANCODE trial: K2 (MK-7) 720 mcg + D3 25 mcg, which is 1,000 IU.
A typical K2-D3 5000 capsule: K2 90 mcg + D3 125 mcg, which is 5,000 IU.
A typical K2-D3 10,000 capsule: K2 45 mcg + D3 250 mcg, which is 10,000 IU.
A K2-only capsule: K2 45 mcg.
Dr. Druz’s general recommendation: K2 90–180 mcg + D3 2,000–5,000 IU.
The DANCODE regimen was the reverse of most combination products: a large amount of K2 alongside only a small amount of D3.
A common combination capsule contains 90 mcg of K2 with 5,000 IU of vitamin D. Taking eight of them to reach the study’s 720 mcg of K2 would also deliver 40,000 IU of vitamin D every day — far beyond a safe intake. Higher-strength D3 versions make this worse, not better: reaching 720 mcg of K2 with a 10,000 IU product would mean 160,000 IU of vitamin D daily.
This is why a research dose is not a recommendation. Matching a study protocol requires separate products and a physician’s supervision — never more capsules of a combination formula.
Dose, form & what to look for
K2: 90–180 mcg/day as MK-7 (not MK-4, which has a shorter half-life and requires 3× daily dosing). D3: 2,000–5,000 IU/day, dose guided by baseline 25-OH vitamin D blood level. Target 50–80 ng/mL. Take both with a fat-containing meal. Recheck vitamin D at 3 months.
Side effects & drug interactions
Vitamin K2 directly affects warfarin’s mechanism. Patients on warfarin must not add K2 without anticoagulation team supervision and more frequent INR monitoring. This is one of the most common supplement-drug interactions Dr. Druz counsels against self-managing.
The DANCODE trial excluded anyone taking warfarin, anyone with a prior stent or bypass, and anyone with a history of blood clots or a clotting disorder — so it offers no evidence about K2 supplementation in those situations.
Frequently asked questions
Does vitamin K2 interact with warfarin?+
Yes — this is one of the most important supplement-drug interactions Dr. Druz counsels against self-managing. Warfarin works by blocking vitamin K-dependent clotting factor activation. Adding K2 supplementation can interfere with INR stability. Patients on warfarin should not add K2 without their anticoagulation team’s supervision and more frequent INR monitoring.
What is the difference between MK-4 and MK-7 forms of K2?+
MK-4 has a half-life of a few hours and requires 3-times-daily dosing to maintain therapeutic levels. MK-7 persists in the body for 72 hours and reaches bone and vascular tissue more reliably at once-daily dosing. Most cardiovascular outcome data maps more closely to MK-7. Dr. Druz recommends MK-7 for cardiovascular patients.
How do I know if I’m deficient in vitamin D?+
The only reliable way is a blood test — specifically 25-OH vitamin D. Dr. Druz measures this at baseline for every new patient and targets 50–80 ng/mL. Deficiency is extremely common, particularly in northern latitudes, in patients who work indoors, and in people with darker skin pigmentation.
Can I get enough K2 from food?+
K2 is found in fermented foods (natto contains very high amounts), aged hard cheeses, and some animal products. Most Western diets are substantially deficient in K2. While dietary sources are valuable, patients with arterial calcification concerns typically need supplemental doses to achieve therapeutic effect.
Is it safe to take high-dose vitamin D long-term?+
High-dose vitamin D above 10,000 IU/day without adequate K2 and magnesium can cause calcium dysregulation and potentially increase arterial calcification risk. At doses of 2,000–5,000 IU/day with K2 MK-7 and magnesium, long-term use guided by blood level monitoring is safe and well-evidenced.
Does the new DANCODE trial mean vitamin K2 removes plaque from my arteries?+
No. Over two years, people taking K2 and D3 accumulated less new arterial calcium than those taking a placebo — a 21% slower rate of buildup, not removal or reversal. Their calcium scores still rose. Total plaque and soft, non-calcified plaque did not change. And while a calcium score is a well-established predictor of cardiac risk, a slower rise in that score has not been shown to mean fewer heart attacks — so the trial’s own authors state it does not establish a role for routine supplementation. It is an encouraging result about a biological mechanism, not proof of clinical benefit.
Should I take the 720 mcg dose used in the trial?+
Not on your own. That is roughly four to eight times a standard supplemental dose, and it was studied in a specific group: average age 71, severe existing calcification, most already taking a statin, with anyone on warfarin, with a clotting disorder, or with a previous stent or bypass excluded. Importantly, you cannot reach it by taking more of a combination capsule — eight capsules of a K2-D3 5000 product would deliver 40,000 IU of vitamin D daily, which is unsafe. Matching a trial regimen requires separate products and a physician’s supervision.
References
- Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease. J Nutr. 2004;134(11):3100–3105.
- Vermeer C, et al. Beyond deficiency: potential benefits of increased intakes of vitamin K. Eur J Nutr. 2004;43(6):325–335.
- Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266–281.
- Hasific S, et al. Vitamin K2 and D3 Supplementation in Patients With Severe Coronary Artery Calcification: The DANCODE Trial. Circulation. 2026;154.
- Daubert MA, Blaha MJ. Coronary Calcium Regression With Vitamin Supplementation: A Therapeutic Target or Too Good to be True? Circulation. 2026;154.
- Vossen LM, et al. Two Years of Menaquinone-7 Supplementation and Coronary Artery Calcification: A Randomized Clinical Trial. JAMA Cardiol. 2026;11:719–726.
- Michos ED, Cainzos-Achirica M, Heravi AS, Appel LJ. Vitamin D, Calcium Supplements, and Implications for Cardiovascular Health. J Am Coll Cardiol. 2021;77:437–449.
This guide is for educational purposes only and does not constitute medical advice. Always consult a qualified physician before starting any supplement, particularly if you are taking anticoagulants, statins, or other cardiovascular medications.
Medically reviewed by Dr. Regina Druz, MD, MBA, FACC, FMCP-M — Board-Certified Integrative Cardiologist at Holistic Heart Centers, Roslyn, NY. Last reviewed: August 2026.
Every supplement we carry comes with a Certificate of Analysis
Supplements are not tested for potency and purity the way prescription medications are. A label claim is a claim, not a verified measurement. That is why the products in our shop are supplied with a Certificate of Analysis — a laboratory report on the specific batch in the bottle.
Identity and composition. Capsule size, weight and disintegration time, tested to United States Pharmacopeia (USP) standards.
Strength. The actual vitamin D3 and vitamin K2 content, measured by HPLC laboratory analysis and confirmed against a defined specification range, so the amounts on the label are verified rather than assumed.
Purity. Testing for total bacterial count, yeast and mould, E. coli and Salmonella.
Contaminants. Heavy metal testing against strict per-capsule limits. On our K2-D3 certificate, arsenic measured at 0.01 mcg against a limit of 10 mcg, and lead, cadmium and mercury were all below the level of detection.
Traceability. The batch lot number, manufacturing date, expiration date and quality-assurance sign-off.
A Certificate of Analysis tells you what is genuinely in the capsule. It does not tell you whether a supplement is right for you — that depends on your own testing, your medications and your cardiovascular risk.
These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, cure, or treat any disease, and are not a substitute for appropriate cardiovascular evaluation with a qualified healthcare professional.
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