What the evidence says. Multiple high-quality RCTs / meta-analyses with consistent effects.
What is Vitamin K1 (Phylloquinone)?
Vitamin K1 (Phylloquinone) is a vitamin used for essential cofactor for hepatic synthesis of functional clotting factors ii, vii, ix and x — corrects/prevents coagulopathy in deficiency. NutriDex grades the human evidence as Strong. Vitamin K1 (phylloquinone) is the predominant dietary form of vitamin K and an essential cofactor for the gamma-carboxylation of clotting factors II, VII, IX and X, as well as bone proteins (osteocalcin) and matrix Gla protein. Frank deficiency is rare in healthy adults but causes impaired coagulation and bleeding; it is a real risk in newborns (hemorrhagic disease of the newborn), fat-malabsorption, and with certain antibiotics, which is why a single intramuscular dose is given at birth. In non-deficient adults, supplementation reliably lowers undercarboxylated osteocalcin, but the largest RCTs (ECKO, 5 mg K1 for 2-4 years) show no protection of bone mineral density, and trials of 500 mcg K1 found no slowing of coronary-artery calcification progression. Benefits beyond correcting deficiency or optimizing carboxylation status are not established for the general population.
Purported Benefits
✓Essential cofactor for hepatic synthesis of functional clotting factors II, VII, IX and X — corrects/prevents coagulopathy in deficiency
✓Standard newborn prophylaxis: a single IM dose prevents vitamin K deficiency bleeding (hemorrhagic disease of the newborn)
✓Reverses warfarin over-anticoagulation and treats vitamin-K-dependent bleeding (clinical antidote)
✓Treats deficiency in fat-malabsorption states (cholestasis, cystic fibrosis, short-bowel, severe IBD)
✓Note: does NOT preserve bone mineral density or prevent coronary-artery calcification in non-deficient adults in large RCTs
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Outcome
Evidence
Effect
Studies
Corrects/prevents coagulopathy in deficiencyEssential clotting cofactor; repletion reliably corrects vitamin-K-dependent bleeding. Established physiology, not a general-population effect.
Strong
↑ benefit · large
2
Reverses warfarin over-anticoagulationClinical antidote; large vitamin K loads predictably alter INR. Well-established, though based on review-level evidence here.
Adequate Intake (AI; no RDA set): 120 mcg/day for adult men, 90 mcg/day for adult women (including pregnancy/lactation). Typical supplements supply ~80-500 mcg; bone/clinical studies have used 1-5 mg K1. No Tolerable Upper Intake Level (UL) has been established because no toxicity has been observed from dietary or supplemental phylloquinone in people not on anticoagulants.
Active Compounds
Phylloquinone (vitamin K1) tablets/drops — the supplemental and pharmaceutical form (e.g., phytonadione)Injectable/oral phytonadione (Mephyton, Konakion) for clinical reversal and newborn prophylaxisDietary: dark leafy greens (kale, spinach, collards, Swiss chard, broccoli, Brussels sprouts)Dietary: vegetable oils (soybean, canola, olive) and foods made with them
Safety & Cautions
⚠
Phylloquinone has very low toxicity and no UL; no adverse effects have been documented from high oral or dietary intake in healthy people. The dominant clinical concern is the interaction with vitamin K antagonist anticoagulants (warfarin/coumarins): changes in vitamin K intake — including supplements and large vegetable meals — alter INR and warfarin effect, so intake should be kept consistent. IV phytonadione has rarely caused anaphylactoid reactions, so it is given slowly/diluted. Phylloquinone does not interact dangerously with DOACs and is not associated with the cancer/CVD harm signals seen with some other supplements. Educational only — always check with your doctor or pharmacist before combining Vitamin K1 (Phylloquinone) with any medicine.
Vitamin K1 (Phylloquinone) drug interactions
Known or theoretical interactions between Vitamin K1 (Phylloquinone) and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Vitamin K1 (Phylloquinone) with any medicine.
Vitamin K1 (Phylloquinone) is most often taken for Essential cofactor for hepatic synthesis of functional clotting factors II, VII, IX and X — corrects/prevents coagulopathy in deficiency, Standard newborn prophylaxis: a single IM dose prevents vitamin K deficiency bleeding (hemorrhagic disease of the newborn), Reverses warfarin over-anticoagulation and treats vitamin-K-dependent bleeding (clinical antidote), Reliably reduces undercarboxylated osteocalcin and matrix Gla protein, improving vitamin-K carboxylation biomarkers. The clotting and bone-carboxylation vitamin from leafy greens
Does Vitamin K1 (Phylloquinone) work — what does the evidence say?
Strong evidence. Multiple high-quality RCTs / meta-analyses with consistent effects. Vitamin K1 (phylloquinone) is the predominant dietary form of vitamin K and an essential cofactor for the gamma-carboxylation of clotting factors II, VII, IX and X, as well as bone proteins (osteocalcin) and matrix Gla protein. Frank deficiency is rare in healthy adults but causes impaired coagulation and bleeding; it is a real risk in newborns (hemorrhagic disease of the newborn), fat-malabsorption, and with certain antibiotics, which is why a single intramuscular dose is given at birth. In non-deficient adults, supplementation reliably lowers undercarboxylated osteocalcin, but the largest RCTs (ECKO, 5 mg K1 for 2-4 years) show no protection of bone mineral density, and trials of 500 mcg K1 found no slowing of coronary-artery calcification progression. Benefits beyond correcting deficiency or optimizing carboxylation status are not established for the general population.
What is the typical dose of Vitamin K1 (Phylloquinone)?
Adequate Intake (AI; no RDA set): 120 mcg/day for adult men, 90 mcg/day for adult women (including pregnancy/lactation). Typical supplements supply ~80-500 mcg; bone/clinical studies have used 1-5 mg K1. No Tolerable Upper Intake Level (UL) has been established because no toxicity has been observed from dietary or supplemental phylloquinone in people not on anticoagulants.
Is Vitamin K1 (Phylloquinone) safe? Any cautions or side effects?
Phylloquinone has very low toxicity and no UL; no adverse effects have been documented from high oral or dietary intake in healthy people. The dominant clinical concern is the interaction with vitamin K antagonist anticoagulants (warfarin/coumarins): changes in vitamin K intake — including supplements and large vegetable meals — alter INR and warfarin effect, so intake should be kept consistent. IV phytonadione has rarely caused anaphylactoid reactions, so it is given slowly/diluted. Phylloquinone does not interact dangerously with DOACs and is not associated with the cancer/CVD harm signals seen with some other supplements.
How many studies support Vitamin K1 (Phylloquinone)?
NutriDex cites 12 sources for Vitamin K1 (Phylloquinone), graded "Strong".
Does Vitamin K1 (Phylloquinone) interact with any medications?
Yes — known or theoretical interactions include: Blood thinners (warfarin, DOACs) (caution). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Vitamin K1 (Phylloquinone) with any medicine.
Cite this page
APA
Peh, D. (2026). Vitamin K1 (Phylloquinone): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/vitamin-k1
BibTeX
@misc{nutridex_vitamin_k1,
author = {Peh, Daryl},
title = {Vitamin K1 (Phylloquinone): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/vitamin-k1},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.