Vitamin K interactions

Vitamin K (in supplements and leafy greens) directly counteracts warfarin, so a steady intake matters more than avoiding it.

Vitamin K has 30 documented interactions across the FDA labels and fact sheets we index: 7 major, 20 moderate, 3 minor, and 0 where a label reports no significant interaction. Each entry below quotes the sentence behind it. This vitamin and mineral page is a starting point, not a verdict for your situation.

Interactions from the label

Major interactions (7)

  • Patients with a hemorrhagic diathesis (e.g., hemophilia, hypoprothrombinemia, von Willebrand's disease, the thrombocytopenias, thrombasthenia and other ill-defined hereditary platelet dysfunctions, severe vitamin K deficiency and severe liver damage). (Butalbital, aspirin, and caffeine label, Contraindications)

  • CapecitabineantimetaboliteMajor

    WARNING: SERIOUS ADVERSE REACTIONS OR DEATH IN PATIENTS WITH COMPLETE DPD DEFICIENCY and INCREASED RISK OF BLEEDING WITH CONCOMITANT USE OF VITAMIN K ANTAGONISTS Increased risk of serious adverse reactions or death in patients with complete DPD deficiency • Test patients for genetic variants of DPYD prior to initiating XELODA unless immediate treatment is necessary. (Capecitabine label, Boxed warning)

  • FondaparinuxanticoagulantMajor

    Do not administer agents that enhance the risk of hemorrhage with fondaparinux sodium unless essential for the management of the underlying condition, such as vitamin K antagonists for the treatment of VTE. (Fondaparinux label, Warnings and precautions)

  • FosphenytoinanticonvulsantMajor

    A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero. (Fosphenytoin label, Warnings and precautions)

  • PhenytoinanticonvulsantMajor

    A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero. (Phenytoin label, Warnings and precautions)

  • RifampinantibioticMajor

    Postmarketing reports suggest that concomitant administration of high doses of cefazolin and rifampin may prolong the prothrombin time, leading to severe vitamin K–dependent coagulation disorders that may be life-threatening or fatal. (Rifampin label, Warnings)

  • WarfarinanticoagulantMajor

    Vitamin K reduces the anticoagulant effect of warfarin; sudden changes in intake from supplements or diet can throw off INR. (NIH Office of Dietary Supplements, Vitamin K)

Moderate interactions (20)

  • ApixabananticoagulantModerate

    For patients with APS (especially those who are triple positive [positive for lupus anticoagulant, anticardiolipin, and anti-beta 2-glycoprotein I antibodies]), treatment with DOACs has been associated with increased rates of recurrent thrombotic events compared with vitamin K antagonist therapy. (Apixaban label, Warnings and precautions)

  • BicalutamideandrogenModerate

    Some patients had serious bleeding including intracranial, retroperitoneal, and gastrointestinal requiring blood transfusion and/or administration of vitamin K. (Bicalutamide label, Warnings and precautions)

  • This can adversely affect patients with inherited (i.e. hemophilia) or acquired (i.e. liver disease or vitamin K deficiency) bleeding disorders. (Butalbital, aspirin, caffeine, and codeine label, Warnings and precautions)

  • CefazolincephalosporinModerate

    Prothrombin time should be monitored in patients at risk and exogenous vitamin K administered as indicated (5.5) (Cefazolin label, Warnings and precautions)

  • CefepimecephalosporinModerate

    Prothrombin time should be monitored in patients at risk, and exogenous vitamin K administered as indicated. (Cefepime label, Warnings and precautions)

  • CefiximecephalosporinModerate

    Prothrombin time should be monitored in patients at risk and exogenous vitamin K administered as indicated. (Cefixime label, Warnings and precautions)

  • CefotetancephalosporinModerate

    Prothrombin time should be monitored and exogenous vitamin K administered as indicated. (Cefotetan label, Warnings)

  • CeftriaxonecephalosporinModerate

    Patients with impaired vitamin K synthesis or low vitamin K stores (e.g., chronic hepatic disease and malnutrition) may require monitoring of prothrombin time during Ceftriaxone for Injection and Dextrose Injection treatment. (Ceftriaxone label, Warnings and precautions)

  • Colesevelambile acid sequestrantModerate

    Vitamin K or Fat-Soluble Vitamin Deficiencies: Colesevelam hydrochloride may decrease absorption of fat-soluble vitamins. (Colesevelam label, Warnings and precautions)

  • DabigatrananticoagulantModerate

    For patients with APS (especially those who are triple-positive [positive for lupus anticoagulant, anticardiolipin, and anti-beta 2-glycoprotein I antibodies]), treatment with DOACs has been associated with increased rates of recurrent thrombotic events compared with vitamin K antagonist therapy. (Dabigatran label, Warnings and precautions)

  • EdoxabananticoagulantModerate

    For patients with APS (especially those who are triple positive [positive for lupus anticoagulant, anticardiolipin antibodies, and anti-beta 2-glycoprotein I antibodies]), treatment with DOACs has been associated with increased rates of recurrent thrombotic events compared with vitamin K antagonist therapy. (Edoxaban label, Warnings and precautions)

  • Levothyroxine and liothyroninethyroid hormoneModerate

    Drug Interactions Oral Anticoagulants — Thyroid hormones appear to increase catabolism of vitamin K-dependent clotting factors. (Levothyroxine and liothyronine label, Drug interactions)

  • Methimazoleantithyroid drugModerate

    Drug Interactions Anticoagulants (oral): Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. β-adrenergic blocking agents: Hyperthyroidism may cause an increased clearance of beta blockers… (Methimazole label, Drug interactions)

  • NeomycinaminoglycosideModerate

    Oral neomycin sulfate may enhance the effect of coumarin in anticoagulants by decreasing vitamin K availability. (Neomycin label, Drug interactions)

  • OrlistatModerate

    The effect of ORLISTAT on the absorption of supplemental vitamin D, vitamin A, and nutritionally-derived vitamin K is not known at this time [see Clinical Pharmacology (12.3) , and Warnings and Precautions (5.1) ] . (Orlistat label, Drug interactions)

  • PentoxifyllinemethylxanthineModerate

    Increased prothrombin time has been reported in patients concomitantly treated with pentoxifylline and vitamin K antagonists. (Pentoxifylline label, Drug interactions)

  • Propylthiouracilantithyroid drugModerate

    Drug Interactions Anticoagulants (oral) : Due to the potential inhibition of vitamin K activity by propylthiouracil, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. (Propylthiouracil label, Drug interactions)

  • QuinineantimalarialModerate

    Warfarin and oral anticoagulants Cinchona alkaloids, including quinine, may have the potential to depress hepatic enzyme synthesis of vitamin K-dependent coagulation pathway proteins and may enhance the action of warfarin and other oral anticoagulants. (Quinine label, Drug interactions)

  • RivaroxabananticoagulantModerate

    For patients with APS (especially those who are triple positive [positive for lupus anticoagulant, anticardiolipin, and anti-beta 2-glycoprotein I antibodies]), treatment with DOACs has been associated with increased rates of recurrent thrombotic events compared with vitamin K antagonist therapy. (Rivaroxaban label, Warnings and precautions)

  • SugammadexModerate

    In vitro experiments demonstrated additional aPTT and PT(INR) prolongations for sugammadex in combination with vitamin K antagonists, unfractionated heparin, low molecular weight heparinoids, rivaroxaban, and dabigatran up to ~25% and ~50% at C max levels of sugammadex corresponding to 4 mg/kg and 16 mg/kg doses, respectively. (Sugammadex label, Warnings and precautions)

Minor mentions (3)

  • Methylergonovineergot alkaloidMinor

    Methylergonovine maleate has been administered instead of vitamin K and Hepatitis B vaccine, medications which are routinely administered to the newborn. (Methylergonovine label, Warnings)

  • Cutaneous Reactions Parenteral administration of vitamin K replacements (including phytonadione injectable emulsion) may cause cutaneous reactions. (Phytonadione (vitamin K1) label, Warnings and precautions)

  • PrimidoneanticonvulsantMinor

    Neonatal hemorrhage, with a coagulation defect resembling vitamin K deficiency, has been described in newborns whose mothers were taking primidone and other anticonvulsants. (Primidone label, Warnings)

Check Vitamin K against everything you take. Add your full list; every pair is checked at once.

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Not medical advice. Severity reflects the label's wording, not your circumstances. A "major" flag can be routine under supervision and a "minor" one can matter at high doses. Ask a pharmacist.