Vitamin K1 (Phylloquinone): Uses, Benefits, Dosage & Safety
Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
Quick summary
Vitamin K1 is the plant form of vitamin K, essential for normal blood clotting. It is the form that interacts strongly with warfarin, so consistency matters for people on that medication.
What is Vitamin K1 (Phylloquinone)?
Vitamin K1 (phylloquinone) is the main dietary form of vitamin K, found in leafy green vegetables. Vitamin K is essential for blood clotting and for proteins involved in bone and blood-vessel health.
What Vitamin K1 (Phylloquinone) is commonly used for
In supplements, Vitamin K1 (Phylloquinone) is most often included for joint & bone health, skin & anti-aging support. It is used as nutritional support, not as a treatment for any medical condition — the distinction matters, because the claims on a sales page are often stronger than the evidence allows.
How Vitamin K1 (Phylloquinone) works
Vitamin K activates clotting factors and other proteins by adding a chemical group they need to function. K1 is taken up mainly by the liver for clotting, while K2 acts more in bone and arteries.
What the evidence says
Here's an honest snapshot of what published research suggests about Vitamin K1 (Phylloquinone) — including where the evidence is limited.
- Vitamin K clearly prevents deficiency bleeding (newborns are given it for this reason). Evidence that extra K1 improves bone or heart health in well-nourished adults is limited and less developed than for K2.
- Study quality and doses vary, and a result seen in research doesn't guarantee the same for any individual — use the sources below to check the current evidence on Vitamin K1 (Phylloquinone) rather than relying on marketing claims.
Typical dosage used in studies
Adequate intake is about 90–120 mcg/day, easily met by eating greens. Supplemental doses vary; people on warfarin should keep their vitamin K intake steady rather than changing it suddenly. This is general information from research, not a personal recommendation or a dosing instruction.
Side effects and safety
Vitamin K1 is generally safe with no established toxicity from food or normal supplements. As with any supplement, it's sensible to introduce Vitamin K1 (Phylloquinone) on its own, use a trusted brand, and stop if you notice any reaction.
Medication interactions and who should avoid Vitamin K1 (Phylloquinone)
Medication & safety check
Vitamins are safe at normal doses, but high-dose supplements can interact with medication and with other nutrients — affecting absorption or blood levels. If you take any regular medication, are pregnant or breastfeeding, or manage a health condition, confirm Vitamin K1 (Phylloquinone) is appropriate for you before starting.
This is general information, not personal medical advice. If you take any medication, are pregnant or breastfeeding, or have a health condition, confirm it's safe to use Vitamin K1 (Phylloquinone) with your doctor or pharmacist first.
Sources & further reading
For authoritative background and the current research base on Vitamin K1 (Phylloquinone), consult:
- PubMed — search the research on Vitamin K1 (Phylloquinone)
- NIH Office of Dietary Supplements — fact sheets
- MedlinePlus (U.S. National Library of Medicine)
- MedlinePlus — drugs, herbs & supplements
Frequently asked questions
Does Vitamin K1 (Phylloquinone) actually work?
Vitamin K clearly prevents deficiency bleeding (newborns are given it for this reason). Evidence that extra K1 improves bone or heart health in well-nourished adults is limited and less developed than for K2. As with most supplements, results vary between people and the marketing is often stronger than the evidence — so it's worth checking the research before relying on it.
Is Vitamin K1 (Phylloquinone) safe to take?
For most healthy adults at normal doses it's generally well tolerated, but there are real cautions. Vitamin K1 is generally safe with no established toxicity from food or normal supplements. If you take medication, are pregnant or breastfeeding, or have a health condition, check with a doctor or pharmacist first.
What is Vitamin K1 (Phylloquinone) used for?
In supplements, Vitamin K1 (Phylloquinone) is mainly included for joint & bone health, skin & anti-aging support — as nutritional support, not as a treatment for any medical condition.
Where you'll find Vitamin K1 (Phylloquinone)
On FactoWiki, Vitamin K1 (Phylloquinone) is the kind of ingredient you'll see discussed in these supplement categories. Each category guide breaks down what the evidence does and doesn't support.
Related ingredients to explore
Ingredients often studied or formulated alongside Vitamin K1 (Phylloquinone) — useful for understanding the full picture of a formula.