Vitamin K2 (Menaquinone) Should Be Taken with Vitamin D
When supplementing with vitamin D, vitamin K2 (specifically menaquinone-7, MK-7) is the preferred form to combine for optimal bone and cardiovascular health. While vitamin K1 (phylloquinone) has some benefit, vitamin K2 menaquinones—particularly MK-4 and MK-7—are more bioactive and effective at activating vitamin K-dependent proteins critical for calcium metabolism 1, 2.
Why Vitamin K2 Specifically
Vitamin K2 menaquinones are significantly more bioactive than vitamin K1 (phylloquinone), which is more abundant in foods but less effective at the tissue level 1.
MK-7 (menaquinone-7) has the longest half-life among vitamin K forms, providing sustained activation of vitamin K-dependent proteins throughout the day 2.
MK-7 has a documented history of safe and effective use with no adverse effects, making it ideal for supplementation 2.
The Synergistic Mechanism
Vitamin D promotes the production of vitamin K-dependent proteins (osteocalcin and matrix Gla-protein), but these proteins require vitamin K for carboxylation to function properly 3, 4.
Without adequate vitamin K, these proteins remain undercarboxylated and cannot effectively chelate calcium from blood to bone, reducing their protective effects on bone density and cardiovascular health 4.
Joint supplementation of vitamins D and K is more effective than either alone for both bone and cardiovascular health, as demonstrated in multiple human intervention studies 3, 5.
Practical Dosing Recommendations
For Vitamin D:
- Standard maintenance: 800-2,000 IU daily of cholecalciferol (D3) for most adults 6, 7.
- For deficiency: 50,000 IU cholecalciferol weekly for 8-12 weeks, followed by maintenance dosing 6, 7.
- Target serum 25(OH)D levels ≥30 ng/mL (75 nmol/L) 6, 7.
For Vitamin K2:
- Typical supplementation ranges from 45-180 mcg/day of MK-7 based on research studies 2, 3.
- Higher doses (up to several milligrams daily) of MK-4 have been used safely in clinical trials, though MK-7 is effective at lower doses 1, 2.
Critical Caveats
Anticoagulation Contraindication:
- Patients receiving warfarin or other vitamin K antagonists should NOT receive vitamin K supplements, as this will interfere with anticoagulation therapy 8.
- This is a firm contraindication in clinical practice 8.
Calcium Intake:
- Ensure adequate calcium intake (1,000-1,500 mg daily) alongside vitamin D and K2 supplementation for optimal bone health 6, 7.
- The combination works synergistically to improve calcium deposition in bone while preventing vascular calcification 3, 4.
Monitoring:
- Check 25(OH)D levels after 3 months of supplementation to ensure adequate response and adjust dosing 8, 6.
- Use an assay that measures both 25(OH)D2 and 25(OH)D3 6, 7.
Special Populations
Children, pregnant/nursing women, and those with malabsorption disorders (cystic fibrosis, inflammatory bowel disease, chronic liver disease) particularly benefit from combined D3 and K2 supplementation 8, 2.
Postmenopausal women have the strongest evidence base for combined supplementation improving bone mineral density and reducing fracture risk 3, 5.