Disclosure: We earn commissions on purchases made through our links. This never influences our scores. Editorial policy
Vitamin K2
The Bottom Line
Vitamin K2 is a fat-soluble vitamin that performs a function most people don't know about: it activates proteins that direct calcium to the right places - bones and teeth - while keeping it out of arteries and soft tissue.
- 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
What Is Vitamin K2?
Vitamin K2 is a fat-soluble vitamin that performs a function most people don't know about: it activates proteins that direct calcium to the right places - bones and teeth - while keeping it out of arteries and soft tissue. This is distinct from Vitamin K1, which primarily supports blood clotting. K1 and K2 are different enough in function that getting plenty of K1 from leafy greens does not protect your cardiovascular system the way K2 does.
The cardiovascular data is the most compelling. The Rotterdam Study (4,807 participants, 10-year follow-up) found that the highest tertile of K2 intake had a 52% lower risk of severe aortic calcification and a 57% lower risk of dying from coronary heart disease compared to the lowest tertile. K1 intake showed no such association. A 2009 Prosper study reinforced these findings. Mechanistically, K2 activates Matrix Gla Protein (MGP), which inhibits arterial calcification. When K2 is deficient, inactive MGP accumulates and calcium deposits in arteries instead of bones.
For bone health, a 2019 meta-analysis by Mott et al. in Osteoporosis International (12 RCTs, 1,261 participants) found MK-7 supplementation significantly increased bone mineral density at the lumbar spine and femoral neck in postmenopausal women. Japanese clinical guidelines recommend MK-4 at 45mg/day (45,000mcg - pharmacological doses) for osteoporosis treatment, but MK-7 at 90-200mcg shows bone benefits at far more practical doses.
The MK-7 form is preferred for supplementation because its longer half-life (72 hours vs 1-2 hours for MK-4) allows once-daily dosing and maintains more consistent tissue saturation. Fermented foods like natto (fermented soybeans) are the richest dietary sources of MK-7. Grass-fed dairy and aged cheeses contain moderate amounts of MK-4. Most Western diets are K2-deficient.
Does It Work? The Evidence
Cardiovascular protection / arterial calcification reduction
Early SignalGeleijnse 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
Early SignalMott et al. 2019 meta-analysis of 12 RCTs (Osteoporosis International); PMID 31076103. Postmenopausal women showed significant BMD increases at lumbar spine
Fracture risk reduction
Early SignalHuang et al. 2015 meta-analysis (Medicine): K2 supplementation reduced fracture incidence vs placebo in Japanese osteoporosis trials
Insulin sensitivity / blood glucose
Not There YetSmall RCTs suggest potential benefit; a 2020 meta-analysis found modest effects on insulin resistance. Evidence is preliminary.
| Claimed Benefit | Evidence Level | Key Studies | Our Verdict |
|---|---|---|---|
| Cardiovascular protection / arterial calcification reduction | Moderate | 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 |
| Bone mineral density improvement | Moderate | Mott et al. 2019 meta-analysis of 12 RCTs (Osteoporosis International); PMID 31076103. Postmenopausal women showed significant BMD increases at lumbar spine | Early Signal |
| Fracture risk reduction | Limited | Huang et al. 2015 meta-analysis (Medicine): K2 supplementation reduced fracture incidence vs placebo in Japanese osteoporosis trials | Early Signal |
| Insulin sensitivity / blood glucose | Limited | 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?
People taking warfarin (Coumadin) or other vitamin K antagonist anticoagulants must consult their doctor, as K2 can interfere with anticoagulant therapy. Even small amounts of K2 can affect INR in patients on warfarin. Note: MK-7's long half-life makes it particularly problematic for this interaction compared to MK-4. Those on other anticoagulants (Xarelto, Eliquis) should still consult their physician. Pregnant women should use prenatal-appropriate K2 dosing.
Side Effects & Safety
Vitamin K2 has an excellent safety profile at supplemental doses. No Tolerable Upper Intake Level has been set by the Institute of Medicine, as no adverse effects have been observed at doses tested in clinical trials. At high doses (above 1,000mcg MK-7), some individuals report mild GI discomfort. The primary clinical concern is the interaction with anticoagulant medications, not toxicity. MK-4 in pharmacological doses used in Japan (45mg/day) has been used safely for decades.
Product Scores
6 products scored on evidence quality, third-party testing, cost per effective dose, and ingredient transparency.
The Scorecard: 6 Products Compared
Sports Research Vitamin K2 + D3
Sports ResearchThe D3+K2 combination is scientifically optimal. One of the best-value combo products on the market with 360 softgels.
100mcg MK-7 combined with 5,000 IU D3 - scientifically rational pairing to support calcium metabolism
Non-GMO Project Verified. Coconut oil as carrier improves fat-soluble vitamin absorption. Third-party tested.
$0.10/day - includes meaningful doses of both K2 and D3; excellent value for the combined product
All ingredients disclosed. MK-7 form specified. Coconut oil carrier listed. Very clean formulation.
100mcg MK-7 combined with 5,000 IU D3 - scientifically rational pairing to support calcium metabolism
Non-GMO Project Verified. Coconut oil as carrier improves fat-soluble vitamin absorption. Third-party tested.
$0.10/day - includes meaningful doses of both K2 and D3; excellent value for the combined product
All ingredients disclosed. MK-7 form specified. Coconut oil carrier listed. Very clean formulation.
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 FormulasOne of the best-priced MK-7 supplements on the market. Matches the dose used in Knapen et al. bone density RCT.
MK-7 form at the established effective dose of 90mcg - matches doses used in primary RCTs
GMP certified facility. Third-party tested. Jarrow has a strong quality track record across its product line.
$0.07/day at 90mcg MK-7 - excellent value for a properly-dosed MK-7 product
Clean label. MK-7 form clearly identified. No proprietary blends. Minimal excipients.
MK-7 form at the established effective dose of 90mcg - matches doses used in primary RCTs
GMP certified facility. Third-party tested. Jarrow has a strong quality track record across its product line.
$0.07/day at 90mcg MK-7 - excellent value for a properly-dosed MK-7 product
Clean label. MK-7 form clearly identified. No proprietary blends. Minimal excipients.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
NOW Foods Vitamin K-2 100mcg
NOW FoodsReliable, affordable, properly dosed. Good starting point for K2 supplementation.
100mcg MK-7 - at the lower end of the effective dose range, consistent with clinical trial dosing
NPA GMP audited facility. NOW has a strong track record. Third-party purity tested.
$0.08/day - strong value for a properly-dosed MK-7 from a reliable brand
Full disclosure. MK-7 form specified. Clean ingredient list.
100mcg MK-7 - at the lower end of the effective dose range, consistent with clinical trial dosing
NPA GMP audited facility. NOW has a strong track record. Third-party purity tested.
$0.08/day - strong value for a properly-dosed MK-7 from a reliable brand
Full disclosure. MK-7 form specified. Clean ingredient list.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Thorne Vitamin K2 (MK-4) 1mg
ThorneThorne'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.
MK-4 form at 1,000mcg - below the 45,000mcg pharmacological dose used in Japanese osteoporosis trials; at this dose MK-4 is less studied than MK-7 for bone/CV outcomes
Thorne manufacturing standards exceed industry norms. Third-party tested. NSF Certified for Sport program.
$0.20/day - premium pricing; the MK-4 form at this dose has less evidence than MK-7 at 100-180mcg
Excellent label disclosure. Form specified as MK-4. Clean formulation. No fillers.
MK-4 form at 1,000mcg - below the 45,000mcg pharmacological dose used in Japanese osteoporosis trials; at this dose MK-4 is less studied than MK-7 for bone/CV outcomes
Thorne manufacturing standards exceed industry norms. Third-party tested. NSF Certified for Sport program.
$0.20/day - premium pricing; the MK-4 form at this dose has less evidence than MK-7 at 100-180mcg
Excellent label disclosure. Form specified as MK-4. Clean formulation. No fillers.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Pure Encapsulations Vitamin K2
Pure EncapsulationsBest choice for those with food sensitivities. Higher 180mcg dose matches the cardiovascular RCT dosing.
180mcg MK-7 - at the higher end of the evidence-based range; matches dose used in the 2015 Knapen arterial stiffness RCT
Third-party tested by Eurofins/Silliker. Hypoallergenic formulation. GMP+ certified. Practitioner-grade quality.
$0.29/day at 180mcg MK-7 - premium pricing for hypoallergenic quality
Exemplary transparency. Every ingredient listed. No fillers. Hypoallergenic certified.
180mcg MK-7 - at the higher end of the evidence-based range; matches dose used in the 2015 Knapen arterial stiffness RCT
Third-party tested by Eurofins/Silliker. Hypoallergenic formulation. GMP+ certified. Practitioner-grade quality.
$0.29/day at 180mcg MK-7 - premium pricing for hypoallergenic quality
Exemplary transparency. Every ingredient listed. No fillers. Hypoallergenic certified.
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 ExtensionComprehensive K complex but the complexity adds cost. People on anticoagulants should be extra cautious with K1+K2 combined.
Multi-form K2 complex: 1,000mcg MK-4 + 100mcg MK-7 + 1,000mcg K1. The K1 component adds blood-clotting support but complicates comparison.
Life Extension quality standards are above industry average. Third-party tested. GMP facility.
$0.22/day - reasonable for a multi-form K complex, but the complexity isn't necessary for most users
All K forms and doses disclosed. No proprietary blend. Clean label. Multi-form approach may confuse buyers who just want K2.
Multi-form K2 complex: 1,000mcg MK-4 + 100mcg MK-7 + 1,000mcg K1. The K1 component adds blood-clotting support but complicates comparison.
Life Extension quality standards are above industry average. Third-party tested. GMP facility.
$0.22/day - reasonable for a multi-form K complex, but the complexity isn't necessary for most users
All K forms and doses disclosed. No proprietary blend. Clean label. Multi-form approach may confuse buyers who just want K2.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Sports Research Vitamin K2 + D3 Sports Research | Jarrow Formulas MK-7 (Vitamin K2 as MK-7) 90mcg Jarrow Formulas | NOW Foods Vitamin K-2 100mcg NOW Foods | Thorne Vitamin K2 (MK-4) 1mg Thorne | Pure Encapsulations Vitamin K2 Pure Encapsulations | Life Extension Super K with Advanced K2 Complex Life Extension |
|---|---|---|---|---|---|---|
| Overall | A- | A- | A- | A- | A- | B+ |
| Evidence | B+ | B+ | B+ | B | B+ | B |
| Quality & Purity | B+ | B+ | B+ | A | A | B+ |
| Value | A- | A | A | B | B | B |
| Transparency | A | A | A | A | A+ | B+ |
| Cost/Day | $0.05Winner | $0.07 | $0.08 | $0.20 | $0.29 | $0.22 |
| Dose/Serving | 100mcg | 90mcg | 100mcg | 1000mcg | 180mcg | 100mcg |
| Form | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | menaquinone-7 (MK-7) | menaquinone-4 (MK-4) | menaquinone-7 (MK-7) | 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.
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.