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    Ingredient guide · Ingredient reference

    What vitamin K1 does: clotting proteins and bone metabolism

    Vitamin K1 is phylloquinone, the main dietary form of vitamin K. Its normal role does not make extra supplementation a proven treatment for every bone or heart problem.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    K1 is a form of vitamin K

    Phylloquinone, or K1, occurs mainly in green leafy vegetables. Vitamin K acts as a coenzyme for an enzyme involved in producing functional vitamin K-dependent proteins. These include clotting proteins and proteins involved in bone metabolism. K1 is not a mineral, and it is not the same molecule as the menaquinones called K2. [1]

    Function is different from extra benefit

    Normal clotting requires vitamin K. That does not mean increasing K1 is a way for a healthy person to improve clotting, or that a supplement is a substitute for assessment of unexplained bleeding. Bone-related protein activation also cannot by itself establish that an additional supplement prevents fractures. NIH ODS describes uncertainty in translating vitamin K supplementation research into routine bone or cardiovascular treatment. [1]

    Why medication changes the interpretation

    Warfarin opposes vitamin K activity. A person taking it should keep vitamin K intake consistent and discuss changes with the prescribing team. Imagine a usual diet suddenly gains a daily K1-containing supplement: this is a new exposure even though the same nutrient occurs in vegetables. Do not change the warfarin dose using a supplement label. [1]

    Hypothetical example — work through the stated example; not a product endorsement or treatment plan
    Hypothetical situationWhat follows
    K1 listed on a multivitaminIdentify the amount and include it in the intake history
    Warfarin plus a planned new K1 supplementDiscuss the change with the treating team
    A claim of stronger bonesNormal nutrient function alone does not prove fracture prevention
    What vitamin K1 does: clotting proteins and bone metabolism — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. Vitamin K - Health Professional Fact Sheet
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.