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Vitamin K1 (Phylloquinone)
The plant form of vitamin K — ESSENTIAL and well-proven for blood clotting (it activates clotting factors). As a supplement for bone/cardiovascular health it's only modestly evidenced, and weaker than vitamin K2 for those uses.
What the evidence says
Vitamin K1 doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from medium-quality randomised trials published 2006–2023 with a typical study size of 35 participants.
Based on 2 studies · 1 RCT · 35 total participants
Confidence
LowBy outcome
Vitamin K1 has an evidence score of 3.8/10 — emerging evidence based on 2 indexed studies. The plant form of vitamin K — ESSENTIAL and well-proven for blood clotting (it activates clotting factors). As a supplement for bone/cardiovascular health it's only modestly evidenced, and weaker than vitamin K2 for those uses. Representative study: PMID 37338608.
The commonly studied dose of Vitamin K1 is Dietary adequacy ~90-120mcg/day; supplements often 100-500mcg. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Explore: Best supplements for Body Health
Last reviewed June 2026 · evidence from 2 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Vitamin K1 (phylloquinone) is the plant form of vitamin K, abundant in leafy greens. Its essential, well-established role is in blood coagulation: it's the cofactor that activates clotting factors II, VII, IX, and X (which is why it's used clinically to reverse warfarin and treat bleeding). As a supplement for bone density or cardiovascular health, the evidence is modest and generally weaker than vitamin K2 (menaquinone), which is preferentially used for extra-hepatic tissues like bone and arteries. Most people get adequate K1 from diet; supplemental K1 is most relevant for documented insufficiency. NOTE: vitamin K interacts strongly with warfarin.
Cofactor for gamma-carboxylation that activates clotting factors II, VII, IX, X.
Activates osteocalcin for bone mineralization (K2 does this more efficiently in bone).
How Vitamin K1 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Dietary adequacy ~90-120mcg/day; supplements often 100-500mcg
Take with food
| Form | Type |
|---|---|
| 💊Phylloquinone (K1) | Recommended |
| 💊Vitamin K2 (MK-7) — better for bone/arteries | Alternative |
K1's proven role is coagulation.
Minimum: 4 weeks
Optimal: 24 weeks
Cycling: Not required
Note: With dietary fat.
Dose-response data unavailable. The current published research for Vitamin K1 does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Essential for blood coagulation.
Adjunctive bone benefit (weaker than K2).
Do NOT change vitamin K intake without clinician guidance — it alters anticoagulation.
Usually met through diet (leafy greens).
Vitamin K directly opposes warfarin — changing intake destabilizes INR. Keep intake consistent and inform your clinician.
Tip: Oral forms are well tolerated
The best time to take Vitamin K1 is with meals. Take it with food. Fat-soluble — take with a fat-containing meal.
Vitamin K1 is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are allergic reaction (rare, IV forms). Use caution if any of these apply to you: Warfarin / vitamin-K-antagonist anticoagulant use (major interaction).
Component of FAD/FMN coenzymes for energy production — high-dose (400mg) clinically shown to reduce migraine frequency.
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