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Vitamin K2 (MK-7) Side Effects & Safety

Evidence:Moderate
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Very well tolerated at standard supplemental doses
  • No known toxicity even at high doses in clinical trials
  • Theoretical concern about hypercoagulability in those with clotting disorders (not documented with K2)
  • Rare: GI discomfort

Drug & Supplement Interactions

  • Warfarin and other vitamin K antagonist anticoagulants — K2 can reduce anticoagulant effectiveness; use only under medical supervision
  • Vitamin D3 — synergistic for bone health; recommended to combine
  • Calcium supplements — K2 helps ensure calcium is deposited in bones rather than arteries
  • Statins — some evidence suggests statins may inhibit K2 synthesis; supplementation may be beneficial

Maximum Dose

Do not exceed: No established upper limit for K2; doses up to 360 mcg MK-7 daily used safely in trials; MK-4 used at 45 mg/day therapeutically in Japan

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References

  1. RCTKnapen MHJ, Drummen NE, Smit E, Vermeer C, Theuwissen E (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International. DOI PubMed
  2. ObservationalGeleijnse JM, Vermeer C, Grobbee DE, et al. (2004). Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. Journal of Nutrition. DOI PubMed
  3. RCTSchurgers LJ, Teunissen KJ, Hamulyák K, Knapen MH, Vik H, Vermeer C (2007). Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. DOI PubMed