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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

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

Compare Forms

3 forms

Different chemical forms vary in absorption, side effects, and best use cases. Higher bioavailability scores indicate better absorption.

K2 as MK-7 (Menaquinone-7)

HIGH 100

Long-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 90

Short-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 75

Plant-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

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

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.

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.

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.