Vitamin K2 Dosage Calculator
The 'calcium traffic director'. MK-7 (menaquinone-7) activates osteocalcin to deposit calcium in bone and matrix Gla protein to prevent arterial calcification — critical for athletes supplementing vitamin D3 and for long-term cardiovascular health.
What is Vitamin K2?
Vitamin K2 (menaquinone) is a fat-soluble vitamin distinct from K1 (phylloquinone, involved in blood clotting). K2 is the essential cofactor for gamma-carboxylation of two proteins critical to calcium homeostasis: osteocalcin (which deposits calcium into bone matrix when carboxylated) and matrix Gla protein, MGP (which prevents calcium deposition in arterial walls when carboxylated). Uncarboxylated osteocalcin and MGP — the inactive forms produced in K2 deficiency — allow calcium to deposit in the wrong tissues: arteries (causing calcification and cardiovascular disease) rather than bone. This explains why vitamin D3 supplementation without adequate K2 may paradoxically increase arterial calcification risk — D3 increases calcium absorption, but without K2, that calcium cannot be properly directed to bone. The MK-7 form (from fermented foods, particularly natto) has a half-life of 72 hours versus < 2 hours for MK-4, achieving superior and more stable tissue saturation with a single daily dose. For athletes, adequate K2 status is also associated with improved testosterone production (via osteocalcin's role in testicular Leydig cell stimulation) and enhanced glycolytic enzyme function.
How to Take Vitamin K2
**General health and calcium direction:** 90–120 mcg/day MK-7 — the adequate intake (AI) established by the European Food Safety Authority. **When supplementing vitamin D3 ≥ 2,000 IU/day:** 100–200 mcg/day MK-7 to ensure sufficient MGP and osteocalcin activation for the additional calcium absorbed. **Cardiovascular risk reduction / arterial health:** 200 mcg/day MK-7 — the dose used in the Rotterdam Study and positive arterial stiffness RCTs. MK-7 is most bioavailable in the all-trans configuration — ensure your product specifies all-trans MK-7. Natto (fermented soy) provides ~1,000 mcg K2 per 100 g — the highest natural food source.
Timing Recommendations
Take with a fat-containing meal — K2 is fat-soluble and requires dietary fat for micellar incorporation. Co-administration with vitamin D3 and vitamin A (all fat-soluble vitamins sharing absorption pathways) is convenient and efficient — the "fat-soluble vitamin triad" of D3 + K2 + A with a fatty meal is the standard protocol. Morning or evening is equivalent as long as dietary fat is present.
Potential Side Effects & Safety
MK-7 at doses up to 360 mcg/day has been well tolerated in all completed clinical trials with no serious adverse events. Unlike K1, K2 at supplemental doses does not meaningfully affect blood coagulation (clotting tests) at doses ≤ 360 mcg/day. Theoretical concern at very high doses (> 1,000 mcg): possible interference with anticoagulant therapy via shared carboxylation pathway.
Who should avoid Vitamin K2?
Warfarin (coumadin) users: K2 is a cofactor for clotting factor carboxylation and may reduce warfarin's anticoagulant effect. Warfarin-anticoagulated patients require physician-supervised K2 dosing with INR monitoring — abrupt introduction or cessation of K2 can destabilise anticoagulation control. DOAC users (rivaroxaban, apixaban, dabigatran) are not affected by K2 and may supplement safely. Soy allergy: MK-7 from natto contains soy; use synthetic all-trans MK-7 from non-soy sources.
Best Stacks with Vitamin K2
The foundational bone and cardiovascular stack: vitamin D3 (2,000–4,000 IU) + vitamin K2 MK-7 (100–200 mcg) + magnesium glycinate (300–400 mg). This trio covers calcium absorption (D3), calcium direction (K2), and calcium utilisation in muscle and nerve (magnesium) simultaneously. For athletes focused on bone density and stress fracture prevention, adding collagen peptides (10 g/day) and calcium from food sources (dairy, fortified foods) completes the structural bone health protocol.
Scientific References
All dosage recommendations are grounded in peer-reviewed research.
- 1Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease (Rotterdam Study)
Journal of Nutrition · 2004
- 2Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in postmenopausal women
Osteoporosis International · 2013
Vitamin K2 Dosage Calculator
Fixed dosage — independent of body weight
Your recommended daily dosage
Formula: 90–120 mcg/day MK-7 (maintenance) | 150–200 mcg/day when co-supplementing vitamin D3 ≥ 2,000 IU
Safety notes
- ALWAYS take with a fat-containing meal — K2 is fat-soluble.
- Warfarin users: K2 can reduce anticoagulant effect — mandatory INR monitoring before adding K2.
- DOAC users (rivaroxaban, apixaban): NOT affected by vitamin K2 — safe to supplement.
- If supplementing vitamin D3 ≥ 2,000 IU/day, K2 (100–200 mcg) is strongly recommended to prevent arterial calcium deposition.
- Use all-trans MK-7 form — check the label. Soy allergy: use synthetic non-natto MK-7.
This calculator provides general guidance only. Always consult a qualified healthcare professional before starting any supplement.