Last verified: 17 days ago
Vitamin K (as Phytonadione)
Also known as: Vitamin K1, Phylloquinone, Phytonadione, Menatetrenone
Evidence under review. — Not yet rated
Fat-soluble vitamin essential for blood clotting and bone health. Well-established nutritional role.
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What it does
Vitamin K1 (phytonadione) is the plant-derived form of Vitamin K, found naturally in leafy green vegetables. It plays a critical role in activating proteins that control blood clotting, preventing...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
90-120 mcg/day (Adequate Intake); higher doses used clinically for specific conditions
What the Science Says
Vitamin K1 (phytonadione) is the plant-derived form of Vitamin K, found naturally in leafy green vegetables. It plays a critical role in activating proteins that control blood clotting, preventing excessive bleeding. It also activates proteins involved in bone mineralization, which is why it is commonly included in bone-health supplement formulas. The Adequate Intake is 90 mcg/day for adult women and 120 mcg/day for adult men, though clinical uses may involve higher doses under medical supervision.
What It Doesn't Do
Won't build strong bones on its own — calcium and Vitamin D do the heavy lifting. No solid evidence it prevents heart disease in otherwise healthy people. Not a treatment for osteoporosis by itself. Taking more than the recommended amount doesn't give extra benefits for most people.
Evidence-Based Benefits
Essential for activating clotting proteins that stop bleeding after injury.
Weak EvidenceEffective at: 90-120 mcg/day
Supports bone mineralization by activating osteocalcin, a key bone-building protein.
Weak EvidenceEffective at: 90-120 mcg/day
Absorption & Bioavailability
Moderate — Vitamin K1 is fat-soluble and absorbed best when taken with a meal containing dietary fat. Absorption is less efficient than Vitamin K2 (MK-7 form). Certain medications and gut conditions can significantly reduce absorption.
Red Flags to Watch For
- Serious interaction with warfarin (Coumadin) and other blood thinners — even small changes in Vitamin K intake can destabilize anticoagulation therapy
- People on anticoagulant medications should never change their Vitamin K intake without consulting a doctor
- Fat malabsorption conditions (e.g., Crohn's disease, celiac disease) can impair absorption and may require medical supervision
- High-dose supplementation has not been proven safe for all populations and should be approached cautiously without medical guidance
Products Containing Vitamin K (as Phytonadione)
See how Vitamin K (as Phytonadione) is used in these analyzed products:
Frequently Asked Questions
What does Vitamin K (as Phytonadione) do?
Fat-soluble vitamin essential for blood clotting and bone health. Well-established nutritional role.
What is the effective dose of Vitamin K (as Phytonadione)?
90-120 mcg/day (Adequate Intake); higher doses used clinically for specific conditions
Is Vitamin K (as Phytonadione) safe?
Serious interaction with warfarin (Coumadin) and other blood thinners — even small changes in Vitamin K intake can destabilize anticoagulation therapy
What doesn't Vitamin K (as Phytonadione) do?
Won't build strong bones on its own — calcium and Vitamin D do the heavy lifting.
Research Sources
- General knowledge — no study abstracts were provided for this analysis. Claims reflect well-established nutritional science, not data from reviewed clinical trials.
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25