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Vitamin K2
K2 is worth taking if you care about arterial calcification or are already supplementing vitamin D3, eating leafy greens for K1 is not a substitute.
- 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.
- →Jarrow MK-7 90mcg ($0.07/day) is the value pick; Sports Research K2+D3 ($0.05/day, 100mcg MK-7 + 5,000 IU D3) is the best combo.
- →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 is worth taking if you care about arterial calcification or are already supplementing vitamin D3, eating leafy greens for K1 is not a substitute. A 10-year study found 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; K1 intake showed no such protection. K2 activates proteins that direct calcium into bones and teeth and keep it out of arteries and soft tissue, a distinct role from K1's blood-clotting function. Most Western diets are K2-deficient.
The cardiovascular data is compelling. A large 10-year study found that 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. K1 intake showed no such protection. K2 activates a protein that inhibits arterial calcification - when K2 is deficient, calcium deposits in arteries instead of bones.
For bone health, reviews of multiple trials show that MK-7 supplementation significantly increases bone mineral density in postmenopausal women. Japanese guidelines use MK-4 at very high pharmacological doses for osteoporosis treatment, but MK-7 at 90-200mcg shows bone benefits at far more practical doses.
MK-7 is preferred for supplementation because its longer half-life (72 hours vs 1-2 hours for MK-4) allows once-daily dosing. Fermented foods like natto are the richest dietary sources. Most Western diets are K2-deficient.
Does It Work? The Evidence
How A-F grades workCardiovascular 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 31076103. 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 31076103. 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 MK-7 daily with a fat-containing meal, as K2 is fat-soluble and absorption is significantly improved when taken with dietary fat. MK-7's long half-life means once-daily dosing is sufficient. Commonly paired with Vitamin D3 - many products combine both. There is no established benefit to taking it at a specific time of day. Consistent daily dosing is more important than timing. Allow 3-6 months for measurable bone density effects.
Who Should Take Vitamin K2?
Postmenopausal women concerned about bone density and fracture risk. People with risk factors for arterial calcification (cardiovascular disease, diabetes, kidney disease). Those taking Vitamin D3 supplements should strongly consider pairing with K2 - D3 increases calcium absorption and K2 ensures it goes to bones rather than arteries. People eating low-K2 diets (minimal fermented foods, grass-fed dairy, or organ meats). People over 50 generally. Anyone 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
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 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Jarrow Formulas MK-7 (Vitamin K2 as MK-7) 90mcg
Jarrow Formulas$4.41 ÷ 63 days at 90mcg/day (1 serving × 90mcg)
One of the best-priced MK-7 supplements on the market. Matches the dose used in Knapen et al. bone density RCT.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
NOW Foods Vitamin K-2 100mcg
NOW Foods$7.49 ÷ 94 days at 100mcg/day (1 serving × 100mcg)
Reliable, affordable, properly dosed. Good starting point for K2 supplementation.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
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 2026-03-01. 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.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Life Extension Super K with Advanced K2 Complex
Life Extension$20.00 ÷ 91 days at 100mcg/day (1 serving × 100mcg)
Comprehensive K complex but the complexity adds cost. People on anticoagulants should be extra cautious with K1+K2 combined.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Pure Encapsulations Vitamin K2 Pure Encapsulations | Jarrow Formulas MK-7 (Vitamin K2 as MK-7) 90mcg Jarrow Formulas | NOW Foods Vitamin K-2 100mcg NOW Foods | Sports Research Vitamin K2 + D3 Sports Research | Thorne Vitamin K2 (MK-4) 1mg Thorne | Life Extension Super K with Advanced K2 Complex Life Extension |
|---|---|---|---|---|---|---|
| Brand Score | 92/100Winner | 91/100 | 91/100 | 90/100 | 90/100 | 84/100 |
| Dosing & Form | 25/25Winner | 25/25 | 25/25 | 25/25 | 25/25 | 25/25 |
| Purity | 23/25Winner | 20/25 | 20/25 | 20/25 | 23/25 | 20/25 |
| Value | 19/25 | 23/25Winner | 23/25 | 22/25 | 19/25 | 19/25 |
| Transparency | 25/25Winner | 23/25 | 23/25 | 23/25 | 23/25 | 20/25 |
| Cost/Day | $0.29 | $0.07 | $0.08 | $0.05Winner | $0.20 | $0.22 |
| Dose/Serving | 180mcg | 90mcg | 100mcg | 100mcg | 1000mcg | 100mcg |
| Form | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | menaquinone-4 (MK-4) | MK-4 + MK-7 + K1 blend |
| 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.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.