Free entry from The Complete Supplement Guide
Vitamin K1 (Phylloquinone)
Graded Strong · Foundational Health · free to read
Vitamin K1 is essential for blood clotting and bone metabolism.
The dose range, the form that actually absorbs, the purity red flags and what not to stack it with are in the guide.
Get The Complete Supplement Guide →Last reviewed September 2026
The verdict
Is Vitamin K1 worth taking?
Vitamin K1 is essential for blood clotting and bone metabolism. It works in the liver, while K2 works in bones and cardiovascular tissue. Both forms are necessary and serve different roles. Leafy greens cover most adults at baseline. Critical flag: K1 directly antagonizes warfarin and other anticoagulant medications. Anyone on blood thinners must not change K1 intake without informing their prescribing physician.
What it does
What Vitamin K1 does in the body
Blood clotting regulation, bone metabolism, and liver health. Vitamin K1 is the primary dietary form of vitamin K and is essential for activating the clotting factors that allow blood to coagulate normally. It is distinct from K2 in both function and distribution. K1 is preferentially used by the liver for clotting protein synthesis while K2 works in bones and cardiovascular tissue. Both forms are necessary and serve different roles.
The evidence
What the research actually shows
Vitamin K1's role in the coagulation cascade is one of the most thoroughly established mechanisms in human physiology. It is the basis for how anticoagulant medications like warfarin work. Evidence for bone health benefits is solid.
Food first
Getting Vitamin K1 from food
Dark leafy greens are the dominant food source. Kale, spinach, collard greens, and Swiss chard provide very high amounts. Broccoli, Brussels sprouts, and green onions are solid secondary sources. For most adults eating a varied diet with regular leafy green consumption, K1 deficiency is uncommon.
What the guide adds
The part that is not on this page
Everything above is the assessment. What the guide adds for Vitamin K1 is the protocol:
- Optimal Form
- Dose Range
- Bioavailability
- Purity Red Flags
- Stack With / Avoid
147 entries across nine categories, every one graded against the clinical literature the same way.
About the author
Who graded this
Daniel Edlund is a Le Cordon Bleu-trained private chef in Los Angeles, a certified personal trainer and strength coach, and an internationally licensed massage therapist. Thirty years of strength training and fifteen years cooking in private estate kitchens. He is the author of The Complete Supplement Guide, which grades 147 entries against the clinical literature, and of The EASY Way to Organic Cooking, first published in 2013.
This page is information, not medical advice. Supplements interact with prescription medication and with each other, and the right answer depends on your own bloodwork and history. Talk to your doctor before starting anything, particularly if you are pregnant, nursing, managing a health condition, or already taking medication.
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