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Vitamin K2
Bottom line
In our scoring, Vitamin K2 rates likely effective: the research is fairly solid for cardiovascular protection / arterial calcification reduction. Our top-scored product is NOW Foods Vitamin K-2 100mcg (85/100), about $0.20 a day at a clinical dose of 90-200mcg MK-7 daily for bone and cardiovascular health. Bottom line: a reasonable pick if it fits your goal. This is our opinion, not medical advice; talk to your clinician before starting.
K2 earns its place if you care about calcium ending up in your bones instead of your arteries, or if you're already taking vitamin D3.
- Evidence
- Likely Effective
- Category
- Vitamins & Minerals
- Best form
- menaquinone-7 (MK-7)
- Effective dose
- 90-200mcg MK-7 daily for bone and cardiovascular health
- Lab tested
- 6 of 6 products
- Category
- Vitamins & Minerals
- Best form
- menaquinone-7 (MK-7)
- Effective dose
- 90-200mcg MK-7 daily for bone and cardiovascular health
- Lab tested
- 6 of 6 products
Key takeaways
- →K2 directs calcium to bones and away from arteries - high K2 intake links to 52% lower severe artery calcification; K1 from leafy greens won't replicate this.
- →Use MK-7 (72-hour half-life, once-daily) at 90-200mcg, not MK-4 - MK-4 only works at the pharmacological 45,000mcg dose used in Japanese osteoporosis trials.
- →NOW Foods K-2 100mcg (~$0.15/day) is the practical MK-7 pick and Life Extension Super K (~$0.14/day) is the cheapest per day; Sports Research K2+D3 (100mcg MK-7 + 5,000 IU D3) is the best combo if you also need D3.
- →Skip if you take warfarin or other vitamin K antagonists without physician oversight - MK-7's long half-life makes this interaction especially problematic.
What Is Vitamin K2?
K2 earns its place if you care about calcium ending up in your bones instead of your arteries, or if you're already taking vitamin D3. Here's the part most people get wrong: loading up on leafy greens gives you K1, and K1 will not do K2's job. The two are cousins, not substitutes. The strongest hint comes from a 10-year study, where people with the highest K2 intake had a 52% lower risk of severe artery calcification and a 57% lower risk of dying from heart disease, while more K1 changed nothing. K2 switches on proteins that act like traffic cops for calcium - steering it into bones and teeth and away from arteries and soft tissue. K1's main job is blood clotting, which is a separate task. Most Western diets run short on K2.
The heart data is where K2 looks most interesting, and it's worth stating the numbers plainly. That large 10-year study found people with the highest K2 intake had a 52% lower risk of severe artery calcification (calcium hardening the arteries) and a 57% lower risk of dying from heart disease. People who ate more K1 got no such protection. The mechanism fits the numbers: K2 activates a protein that keeps calcium out of artery walls, and when K2 is in short supply, that calcium tends to settle in arteries instead of bones.
For bones, reviews pooling multiple trials show MK-7 meaningfully raises bone mineral density in postmenopausal women. Japan treats osteoporosis with MK-4 at very high pharmacological doses, but you don't need that - MK-7 at 90-200mcg delivers bone benefits at a far more practical dose.
One reason MK-7 is the supplemental form worth buying: it sticks around in your body much longer. Its half-life (how long it takes the level in your blood to drop by half) is 72 hours, versus just 1-2 hours for MK-4, so a single daily capsule keeps levels steady. If you want it from food, fermented foods like natto are the richest source. Most Western diets are K2-deficient.
Does It Work? The Evidence
How A-F grades workVitamin K2 earns a Likely Effective rating on the strength of its best-supported uses: cardiovascular protection / arterial calcification reduction and bone mineral density improvement (grade B). The table below grades every claimed benefit on its own, including weaker and more heavily marketed uses, so one strong result never stands in for the rest.
Cardiovascular protection / arterial calcification reduction
Geleijnse et al. 2004 Rotterdam Study (J Nutr); PMID 15514282. Beulens et al. 2009 EPIC-NL cohort study. Knapen et al. 2015 three-year MK-7 RCT (Thrombosis and Haemostasis)
Bone mineral density improvement
Mott et al. 2019 meta-analysis of 12 RCTs (Osteoporosis International); PMID 31076817. Postmenopausal women showed significant BMD increases at lumbar spine
Fracture risk reduction
Huang et al. 2015 meta-analysis (Medicine): K2 supplementation reduced fracture incidence vs placebo in Japanese osteoporosis trials
Insulin sensitivity / blood glucose
Small RCTs suggest potential benefit; a 2020 meta-analysis found modest effects on insulin resistance. Evidence is preliminary.
| Grade | Claimed Benefit | Key Studies | Our Verdict |
|---|---|---|---|
| B | Cardiovascular protection / arterial calcification reduction | Geleijnse et al. 2004 Rotterdam Study (J Nutr); PMID 15514282. Beulens et al. 2009 EPIC-NL cohort study. Knapen et al. 2015 three-year MK-7 RCT (Thrombosis and Haemostasis) | Early Signal |
| B | Bone mineral density improvement | Mott et al. 2019 meta-analysis of 12 RCTs (Osteoporosis International); PMID 31076817. Postmenopausal women showed significant BMD increases at lumbar spine | Early Signal |
| C | Fracture risk reduction | Huang et al. 2015 meta-analysis (Medicine): K2 supplementation reduced fracture incidence vs placebo in Japanese osteoporosis trials | Early Signal |
| C | Insulin sensitivity / blood glucose | Small RCTs suggest potential benefit; a 2020 meta-analysis found modest effects on insulin resistance. Evidence is preliminary. | Not There Yet |
How to Choose: Forms, Doses & What Matters
Clinical dose: 90-200mcg MK-7 daily for bone and cardiovascular health; MK-4 requires higher doses (1,500mcg) due to shorter half-life - MK-7 is the preferred supplemental form
Best forms: menaquinone-7 (MK-7), menaquinone-4 (MK-4) at 1,500mcg+
Take 100-200mcg of MK-7 once a day, and take it with a meal that has some fat in it - K2 is fat-soluble, so a little dietary fat noticeably improves how much you absorb. Because MK-7 lingers in your system, one capsule a day covers you; you don't need to split doses. It pairs naturally with vitamin D3, which is why so many products bundle the two. Time of day doesn't matter - no clock-watching required. What does matter is taking it consistently. And give it time: plan on 3-6 months before bone density effects show up on a measurement.
Who Should Take Vitamin K2?
If you're a postmenopausal woman worried about bone density and fractures, this is squarely aimed at you. So is anyone with risk factors for arterial calcification - calcium hardening the arteries - such as cardiovascular disease, diabetes, or kidney disease. The clearest case is if you already take vitamin D3: D3 pulls more calcium into your body, and K2 is what helps send that calcium to your bones rather than your arteries, so the two work as a pair. You're also a good candidate if your diet is low in K2 (you rarely eat fermented foods, grass-fed dairy, or organ meats), if you're over 50, or if you're on a long-term high-dose vitamin D3 protocol.
Who Should Avoid It?
Not for everyone
Side Effects & Safety
Product Scores
6 products scored on dosing accuracy, third-party testing, cost per effective dose, and label transparency.
The Scorecard: 6 Products Compared
Sports Research Vitamin K2 + D3
Sports Research$17.95 ÷ 359 days at 100mcg/day (1 serving × 100mcg)
The D3+K2 combination is scientifically optimal. One of the best-value combo products on the market with 360 softgels.
Prices checked 2026-06-30. Cost shown is per clinically effective daily dose, not per pill.
Thorne Vitamin K2 (MK-4) 1mg
Thorne$12.00 ÷ 60 days at 1000mcg/day (1 serving × 1000mcg)
Thorne's quality is excellent. However, MK-7 is the better-studied form for supplemental dosing - this MK-4 product is below the therapeutic dose used in Japanese trials. buyUrl blanked pending a scoped rewrite (see TODO): the linked ASIN is actually a liquid, not this capsule.
Prices checked 2026-06-30. Cost shown is per clinically effective daily dose, not per pill.
Pure Encapsulations Vitamin K2
Pure Encapsulations$17.50 ÷ 60 days at 180mcg/day (1 serving × 180mcg)
Best choice for those with food sensitivities. Higher 180mcg dose matches the cardiovascular RCT dosing.
Prices checked 2026-06-30. Cost shown is per clinically effective daily dose, not per pill.
NOW Foods Vitamin K-2 100mcg
NOW Foods$20.35 ÷ 102 days at 100mcg/day (1 serving × 100mcg)
Reliable, affordable, properly dosed. Good starting point for K2 supplementation.
Prices checked 2026-06-30. Cost shown is per clinically effective daily dose, not per pill.
Life Extension Super K with Advanced K2 Complex
Life Extension$12.95 ÷ 92 days at 100mcg/day (1 serving × 100mcg)
Comprehensive K complex and the cheapest per-day option here. The K1 component means people on anticoagulants should be extra cautious - a trade-off, not a pure bonus, if you specifically want K2's benefits.
Prices checked 2026-06-08. Cost shown is per clinically effective daily dose, not per pill.
Jarrow Formulas MK-7 (Vitamin K2 as MK-7) 90mcg
Jarrow Formulas$16.99 ÷ 61 days at 90mcg/day (1 serving × 90mcg)
Matches the dose used in the Knapen et al. bone density RCT. Once one of the best-priced MK-7s, though its price has risen well above the budget tier.
Prices checked 2026-06-08. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Sports Research Vitamin K2 + D3 Sports Research | Thorne Vitamin K2 (MK-4) 1mg Thorne | Pure Encapsulations Vitamin K2 Pure Encapsulations | NOW Foods Vitamin K-2 100mcg NOW Foods | Life Extension Super K with Advanced K2 Complex Life Extension | Jarrow Formulas MK-7 (Vitamin K2 as MK-7) 90mcg Jarrow Formulas |
|---|---|---|---|---|---|---|
| Brand Score | 87/100Winner | 87/100 | 87/100 | 85/100 | 84/100 | 84/100 |
| Dosing & Form | 25/25Winner | 25/25 | 25/25 | 25/25 | 25/25 | 25/25 |
| Purity | 20/25 | 23/25Winner | 23/25 | 20/25 | 20/25 | 20/25 |
| Value | 19/25Winner | 16/25 | 14/25 | 17/25 | 19/25 | 16/25 |
| Transparency | 23/25 | 23/25 | 25/25Winner | 23/25 | 20/25 | 23/25 |
| Cost/Day | $0.05Winner | $0.20 | $0.29 | $0.20 | $0.14 | $0.28 |
| Dose/Serving | 100mcg | 1000mcg | 180mcg | 100mcg | 100mcg | 90mcg |
| Form | menaquinone-7 (MK-7) | menaquinone-4 (MK-4) | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | MK-4 + MK-7 + K1 blend | menaquinone-7 (MK-7) |
| Third-Party Tested | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes |
| Proprietary Blend | No | No | No | No | No | No |
Frequently Asked Questions
What is the difference between K1 and K2?
Vitamin K1 (phylloquinone) is found in leafy greens and primarily supports blood clotting. Vitamin K2 (menaquinone) is found in fermented foods and animal products and primarily activates proteins that regulate calcium distribution - directing it to bones and teeth while keeping it out of arteries. They are related but perform distinct functions. Getting enough K1 does not substitute for K2.
Should I take MK-4 or MK-7?
MK-7 is the preferred form for supplementation. Its half-life is 72 hours vs 1-2 hours for MK-4, so it maintains higher, more consistent tissue levels with a once-daily dose of 90-200mcg. MK-4 is used at pharmacological doses (45,000mcg) in Japanese osteoporosis treatment, but that dose is impractical and unnecessary for most supplementers. The bone and cardiovascular evidence for MK-7 at practical doses (90-180mcg) is solid.
Should I take K2 with Vitamin D3?
Yes - the combination is well-supported. Vitamin D3 increases calcium absorption from the gut. Without adequate K2, that extra absorbed calcium can end up in arteries rather than bones. K2 activates osteocalcin (bone-building) and Matrix Gla Protein (arterial protection), which require K2 for activation. Many practitioners and experts recommend taking K2 alongside any significant D3 supplementation. A ratio of 100mcg K2 per 2,000 IU D3 is commonly recommended.
What foods are highest in K2?
Natto (fermented soybeans) is by far the richest source of MK-7, with 850-1,000mcg per 100g serving. Other fermented cheeses contain MK-7 in smaller amounts. Egg yolks, liver, dark chicken meat, and full-fat dairy from grass-fed animals contain MK-4. Most modern Western diets provide very little K2 since natto is uncommon and much dairy and meat comes from grain-fed animals.
How long does it take for K2 to work for bone health?
Bone remodeling is slow. Studies measuring bone mineral density typically run 12-36 months. The 2015 Knapen et al. RCT ran for 3 years before showing significant BMD improvement with 180mcg MK-7. For cardiovascular markers like arterial stiffness, some studies show measurable changes at 6-12 months. This is a long-game supplement - consistent use over years is what produces measurable outcomes.
Related Articles
Sources
- Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr. 2004;134(11):3100-3105.
- Knapen MH, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499-2507.
- Knapen MH, et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women: double-blind randomised clinical trial. Thromb Haemost. 2015;113(5):1135-1144.
- Mott A, et al. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Osteoporos Int. 2019;30(8):1543-1559.
- NIH Office of Dietary Supplements. Vitamin K Fact Sheet for Health Professionals. Updated 2023.
- Beulens JW, et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis. 2009;203(2):489-493.
Scores and tiers are our independent opinion, formed by applying a published rubric to label data, third-party certifications, and the research record. They are not statements of objective fact about a product and not a lab test. Where we report a brand-specific fact, it comes from a cited source or a public certification; where verification is missing, we say so rather than assume a result.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.