Vitamin K
Vitamin3 forms compared ↓
Also known as: K1, Phylloquinone, Phytonadione, Vitamin K, vitamin-k
A
Grade A💊 90-120 mcg daily (RDA)🎯 6 primary uses🔗 1 synergy⚠️ Review warnings
Levels upNutrition+50 pts
Overview
A fat-soluble vitamin essential for blood clotting, bone metabolism, and cardiovascular health. Phytonadione (K1) is the plant-derived form found in leafy greens and the primary supplemental form.
Primary Uses
Blood clottingCoagulation supportBlood clotting supportBone health and mineralizationCardiovascular healthProtein carboxylation
Frequently Asked About Vitamin K
How much Vitamin K should I take?
The typical effective range is 180-360 mcg K2 (MK-7). Individual needs vary based on age, body weight, diet, and goals — start at the lower end and adjust based on response. Always consult a healthcare provider before starting a new supplement.
When is the best time to take Vitamin K?
With fat. Consistency matters more than perfect timing — pick a daily anchor (e.g. with breakfast or before bed) and stick with it.
Should I take Vitamin K with food?
Yes.
What is the best form of Vitamin K?
K2 as MK-7 (Menaquinone-7) is generally the best-absorbed form (Long-chain K2 from natto fermentation). Cheaper forms exist but often deliver less usable Vitamin K per dose.
Does Vitamin K interact with medications?
Yes — known interactions include Warfarin - must keep intake consistent. If you take any prescription medication, talk to your doctor or pharmacist before starting Vitamin K.
What does Vitamin K pair well with?
Vitamin K stacks well with Fat for absorption — these combinations either improve absorption or work synergistically toward common goals.
Who should not take Vitamin K?
Vitamin K should be avoided or used with caution by people with Warfarin users (without physician guidance) and Other vitamin K antagonist anticoagulants. Pregnant or breastfeeding women should consult a healthcare provider before use.
Compare Forms
3 formsDifferent chemical forms vary in absorption, side effects, and best use cases. Higher bioavailability scores indicate better absorption.
K2 as MK-7 (Menaquinone-7)
HIGH 100Long-chain K2 from natto fermentation
Best for:Bone healthCardiovascular calcification preventionOnce-daily dosing
💡 Excellent. Half-life of 3 days means once-daily dosing works.
✅ Pros
- • Long half-life
- • Best vascular protection data
- • Synergizes with vitamin D
⚠️ Cons
- • Expensive
- • Can interact with warfarin (avoid if on blood thinners)
📝 Best general K2 choice. Pair with vitamin D3 + magnesium.
K2 as MK-4 (Menatetrenone)
HIGH 90Short-chain K2; the form found in animal foods
Best for:Bone health (high-dose Japanese protocols)Hormonal support
💡 Good but very short half-life — requires multiple doses per day.
✅ Pros
- • Strong bone-density evidence at high doses (45 mg/day)
- • May support testosterone
⚠️ Cons
- • Multiple daily doses needed
- • Therapeutic doses are very high
📝 Less convenient than MK-7 for general use. Therapeutic role at 45 mg in osteoporosis.
K1 (Phytonadione/Phylloquinone)
GOOD 75Plant-form vitamin K, primarily for blood clotting
Best for:Coagulation supportNewborn vitamin K injection (medical)
💡 Good with fat. Mostly retained by the liver; less reaches bones/arteries.
✅ Pros
- • Cheapest
- • Found in leafy greens
- • Reliable for clotting
⚠️ Cons
- • Limited extra-hepatic activity
- • Doesn't replace K2 for bone/vascular needs
📝 K2 is preferred for supplementation. Get K1 from leafy greens instead.
Dosage
Typical range
90-120 mcg daily (RDA)
Timing
With fat
With food
Yes
Dose Tiers
RDA / DV
90-120 mcg
Moderate
100-200 mcg
Optimal
180-360 mcg K2 (MK-7)
Therapeutic
45 mg K2 (MK-4)
Upper Limit
No established UL
Duration
Usually adequate from diet
Special Populations
Those on warfarin need consistent intake
Research & Studies
Search the literature now
We haven’t curated landmark studies for Vitamin Kyet — one-click into the primary literature here. PubMed (RCTs) is usually the highest-signal starting point.
Mechanism of Action
- • Essential cofactor for clotting factors II, VII, IX, X
- • Rapidly cleared from circulation
- • Converts to MK-4 in some tissues
Evidence Quality
Evidence Grade A
Essential for coagulation
Safety & Contraindications
Serious Warnings
- • CRITICAL: Reverses warfarin anticoagulant effect
- • Warfarin users must consult physician before use
- • Keep vitamin K intake consistent if on blood thinners
Contraindications
- • Warfarin users (without physician guidance)
- • Other vitamin K antagonist anticoagulants
Common Side Effects
- • Very safe
Pregnancy & Breastfeeding
Consult healthcare provider
Liver & Kidney Notes
Safe
Interactions
💊 Medications
- • Warfarin - must keep intake consistent
🧪 Supplements
- • K2 preferred for bone/heart
🍽️ Food & Alcohol
- • Green vegetables
Stacking & Synergies
Pairs Well With
Fat for absorption
Avoid Combining With
Variable intake on warfarin
Best Goal Synergies
Basic K needs
Buying Guide
What to Look For
- • Adequate dose
Standardization Markers
mcg content
Adulteration risk
Low
Practical Notes
- • K2 preferred for bone/heart benefits
- • Abundant in diet
Tags
fat-solubleclottingessentialessential nutrientbone healthcardiovascular health
Top Products with Vitamin K
Highest-scored catalog products containing Vitamin K, ranked by our scoring engine.
Browse all Vitamin K products →
Related Guides
In-depth guides covering Vitamin K — protocols, comparisons, and use cases.
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Last reviewed: August 2026 by the Formulate Research Team. Sources cited above; methodology and scoring criteria published here.
Cite this page
Formulate Research Team. (2026, August). Vitamin K — Evidence-Based Supplement Guide. Formulate Supplement Encyclopedia. https://app.formulate-health.app/learning/supplements/vitamin-k
Educational content based on published research and our scoring methodology. Not medical advice — consult a qualified healthcare provider before starting, stopping, or changing supplements, especially if you take medications, are pregnant, or have a medical condition.