Vitamin K2 (MK-7) has 2 documented interactions in Magellan’s curated dataset, covering Anticoagulants (blood thinners), Cephalosporin antibiotics. Each entry below gives the mechanism as the cited reference states it, the direction the risk runs, how serious that reference treats it, and what to actually do about it — which is, in every case, a conversation with the clinician or pharmacist who manages the prescription rather than a decision you make alone.
What it is. Vitamin K2 (menaquinone) is a fat-soluble vitamin obtained from fermented foods such as natto and some cheeses and synthesized by gut bacteria; MK-7 (menaquinone-7) is a long-chain menaquinone valued for its high bioavailability and long circulating half-life. It functions as an essential cofactor for the enzyme that γ-carboxylates vitamin K-dependent proteins, including matrix Gla-protein (MGP) in the arterial wall and osteocalcin in bone.
Where it sits on the evidence. Magellan grades the supplement itself as Moderate evidence, with a typical studied dose of 180 µg/day MK-7 in the main 3-year arterial-stiffness trial. That grade is about whether it works, not about whether it is safe alongside your medication — the two questions are independent, and this page answers only the second.
Products this covers: Vitamin K2 (MK-7).
How the risks cluster. Every entry on this page runs through the same mechanism — opposing — which means one conversation covers all of them.
Safety and efficacy are separate questions, and this page only answers the first. For the second, the study Magellan’s coverage of Vitamin K2 rests on is:
“vitamin K supplementation prevented progression of arterial stiffness compared with placebo”
A strong result does not make a supplement safe alongside your prescription, and a documented interaction does not mean the supplement does not work. Magellan grades those two things separately, and neither grade moves for a commission.
Magellan’s Medication Safety Check runs entirely on your device — type the medicines you take and it flags every documented interaction in this dataset. Nothing you type is sent anywhere.
Open the Medication Safety Check →Vitamin K directly opposes how these anticoagulants work (they act by depleting vitamin K-dependent clotting factors), so vitamin K intake - including from supplements - can reduce the drug's effectiveness and destabilize INR control; NIH describes this as a serious and potentially dangerous interaction requiring consistent intake and medical supervision.
Medicines in this group include: Warfarin (Coumadin, Jantoven), Apixaban (Eliquis), Rivaroxaban (Xarelto), Dabigatran (Pradaxa), Edoxaban (Savaysa), Heparin (Lovenox, Enoxaparin), Acenocoumarol (Sintrom).
These antibiotics can reduce vitamin K-producing gut bacteria and may inhibit vitamin K action in the body; supplementation is generally unnecessary unless antibiotic use is prolonged with poor dietary vitamin K intake.
Medicines in this group include: Cephalexin (Keflex), Cefdinir (Omnicef), Ceftriaxone (Rocephin).
These are the warning signs that go with the medication classes on this page. They are general safety-netting, not a prediction that any supplement will cause them.
If something feels seriously wrong, do not wait for an appointment. Call 911 (US) or your local emergency number.
Severity describes the interaction as the cited reference frames it, not how a specific person will react. A “minor” entry in someone with kidney disease, on five other drugs, can matter more than a “major” one in someone on nothing else.
This is a curated set of interactions with citations — not an exhaustive pharmacology database. An interaction that is absent here has not been ruled out; it may simply not be documented in the references Magellan curates from. Supplements are also not batch-tested for identity or contamination the way prescription drugs are, so what is on the label is a claim rather than a guarantee. And most of these entries come from case reports and mechanistic work rather than randomized trials, which is exactly why the sensible response is a pharmacist review rather than either alarm or dismissal.
22 documented interactions across 17 supplements.
7 documented interactions across 6 supplements.
8 documented interactions · shares a drug class with Vitamin K2.
7 documented interactions · shares a drug class with Vitamin K2.
5 documented interactions · shares a drug class with Vitamin K2.
5 documented interactions · shares a drug class with Vitamin K2.
The mechanism and the research behind the compound itself.
A–Z of every supplement and drug class in this dataset, plus how to read an interaction.
What the research actually shows, graded independently of affiliate commissions.
Not without checking with the prescriber or pharmacist first. Magellan's dataset grades this as a major interaction: Vitamin K directly opposes how these anticoagulants work (they act by depleting vitamin K-dependent clotting factors), so vitamin K intake - including from supplements - can reduce the drug's effectiveness and destabilize INR control; NIH describes this as a serious and potentially dangerous interaction requiring consistent intake and medical supervision. (Source: Vitamin K - Health Professional Fact Sheet, Office of Dietary Supplements.)
2 interactions are documented in Magellan's curated dataset: 1 major, 1 minor. They cover Anticoagulants (blood thinners), Cephalosporin antibiotics. Absence from this list is not proof of safety — it means no interaction is documented in the references we curate from.
Magellan lists the typical studied dose as: 180 µg/day MK-7 in the main 3-year arterial-stiffness trial. Dose matters for interactions — several of the entries on this page describe effects that only appear at supplemental rather than dietary intakes.