Anticoagulants such as warfarin, apixaban and rivaroxaban, and antiplatelet drugs such as aspirin and clopidogrel, deliberately reduce your blood's ability to clot. Supplements that also act on platelets, on clotting factors, or on vitamin K can add to that effect — or, in the case of vitamin K, work against it. This is the largest interaction cluster in the Magellan dataset.
Below is every interaction Magellan documents for this class — 22 entries across 17 supplements, each with the mechanism as the cited reference states it, how serious that reference treats it, and where to take the question next.
One caveat on how to weigh them. 1 of the 22 entries below are marked class-level caution: the source flags a broad group of drugs that share a metabolic pathway — usually CYP3A4 — rather than reporting a finding about a named medicine. Those are weaker than the entries that name a specific drug, and they are labelled so you can tell the difference rather than being quietly padded in.
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 →Fish oil has mild antiplatelet activity and can prolong clotting time/raise INR when combined with blood thinners; most studies of 3-6 g/day fish oil do not cause significant bleeding, but periodic INR monitoring is advised for those on warfarin.
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.
CoQ10 may make warfarin (Jantoven) less effective at thinning the blood, which could raise the risk of a dangerous blood clot; Mayo Clinic and NCCIH both flag this interaction.
In an animal pharmacokinetic study, resveratrol increased warfarin exposure and INR via CYP2C9/BCRP inhibition; the authors cautioned that warfarin-treated patients should be aware of a hidden bleeding risk from resveratrol supplementation. Resveratrol also has antiplatelet activity that can add to bleeding risk with blood thinners.
Quercetin has documented in-vitro antiplatelet activity and inhibits CYP3A4/P-glycoprotein, which could theoretically raise blood levels of drugs like cyclosporine or add to bleeding risk with blood thinners.
Pomegranate juice may slow the breakdown of warfarin, increasing its blood-thinning effect and bleeding risk; INR monitoring is advised.
Hesperidin (commonly studied combined with diosmin, as in venous-insufficiency products) may slow blood clotting and interfere with anticoagulant metabolism; a Health Canada safety review linked diosmin/hesperidin products to increased bleeding risk, including cases in patients on anticoagulants, prompting mandated label warnings.
Grape seed extract shows antiplatelet activity in vitro and may add to the risk of bleeding-related side effects when combined with blood thinners; clinical significance in humans is not yet firmly established.
Carnitine/acetyl-L-carnitine may have additive anticoagulant effects; a published case report documented potentiation of the oral anticoagulant acenocoumarol by L-carnitine supplementation, and warfarin is listed as a drug that usually should not be combined with levocarnitine without dose adjustment and monitoring.
L-carnitine may increase the anticoagulant effect of warfarin/acenocoumarol, raising bruising and bleeding risk; more frequent INR monitoring and possible dose adjustment are recommended.
Taking glucosamine alone or with chondroitin may increase the anticoagulant effect of warfarin, raising the risk of bleeding and elevated INR; this has been documented in case reports and reviewed in the pharmacotherapy literature.
Glucosamine, alone or combined with chondroitin, has documented case reports and pharmacologic data showing it can potentiate warfarin's effect and raise INR, increasing bleeding risk.
MSM is sometimes flagged as having mild blood-thinning activity of its own, so combining it with prescription anticoagulants could theoretically add to bleeding risk; evidence is limited.
Possible additive effect on bleeding/GI risk when combined with regular NSAID use; documentation is limited compared to other supplement-anticoagulant interactions.
Ginger has the strongest documented evidence in this blend: case reports include elevated INR and bleeding on phenprocoumon and a fatal GI bleed on dabigatran, and it is recommended to stop ginger 2 weeks before surgery. Glucosamine sulfate and pterostilbene each separately carry documented or plausible anticoagulant-potentiating/antiplatelet effects, compounding the concern for anyone on warfarin, DOACs, or antiplatelet therapy.
Nattokinase can enhance the antiplatelet effect of aspirin and other antiplatelet drugs, with documented reports of increased bleeding, including intracerebral hemorrhage; contraindicated in people with coagulation disorders or a history of DVT.
Contains nattokinase, a fibrinolytic enzyme; nattokinase increases bleeding risk with anticoagulants and, because the natto fermentation process continues producing vitamin K in the gut, may also reduce warfarin's effectiveness - a combination that makes anticoagulation control unpredictable. Should be stopped before surgery.
Rutin, a bioflavonoid in this blend, may alter warfarin blood levels and effect; more frequent INR monitoring is recommended when combined.
This is a mixed polyphenol/flavonoid blend; multiple polyphenol classes (resveratrol-like stilbenes, quercetin-like flavonols, and related bioflavonoids such as rutin) independently inhibit platelet aggregation and/or potentiate warfarin in documented case reports, so a blend combining several such compounds carries an additive bleeding-risk concern with blood thinners.
Taurine may interfere with cytochrome P450 enzymes used to metabolize these drug classes at supplemental (not typical energy-drink) doses, though this is a general mechanism-based caution rather than itemized per-drug clinical data.
Boswellic acid compounds can inhibit platelet aggregation, which may add to the bleeding risk of blood-thinning medications.
Pine bark extract may inhibit platelet aggregation, which could add to the bleeding risk of blood-thinning medications.
Medicines in this group include: Warfarin (Coumadin, Jantoven), Apixaban (Eliquis), Rivaroxaban (Xarelto), Dabigatran (Pradaxa), Edoxaban (Savaysa), Heparin (Lovenox, Enoxaparin), Acenocoumarol (Sintrom), Aspirin (Asa, Bayer aspirin), Clopidogrel (Plavix), Ticagrelor (Brilinta), Prasugrel (Effient), Dipyridamole (Aggrenox, Persantine).
Brand names are listed in brackets after the generic ingredient. If the name on your bottle is not here, the generic name on the label almost always is — and the Medication Safety Check accepts either.
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.
3 documented interactions in total.
2 documented interactions in total.
4 documented interactions in total.
2 documented interactions in total.
2 documented interactions in total.
4 documented interactions in total.
3 documented interactions in total.
2 documented interactions in total.
7 documented interactions in total.
5 documented interactions in total.
2 documented interactions in total.
8 documented interactions in total.
4 documented interactions in total.
3 documented interactions in total.
1 documented interaction in total · covered on the hub.
1 documented interaction in total · covered on the hub.
1 documented interaction in total · covered on the hub.
Blood pressure medications · Diabetes medications · Statins · Cancer treatment · Antibiotics · Immunosuppressants · Diuretics · Other drug classes
Back to the full supplement–drug safety hub → · The evidence-graded supplement guide →
Omega-3 (EPA/DHA fish oil), Vitamin K2 (MK-7), CoQ10 / ubiquinol, Resveratrol, Quercetin, Pomegranate ellagitannins, Hesperidin (citrus flavonoid), Grape seed extract, Carnitine (L-carnitine and acetyl-L-carnitine), Glucosamine and chondroitin, MSM (methylsulfonylmethane), NOVOS Core (multi-ingredient formula), NOVOS Vital Organ Support, DaVinci Labs Phyto Benefits, Taurine, Boswellia serrata, Pycnogenol (pine bark extract) — 22 documented entries in total (7 major, 11 moderate, 4 minor). Each entry on this page names the reference it came from.
In this dataset the class includes Warfarin, Apixaban, Rivaroxaban, Dabigatran, Edoxaban, Heparin and others. Brand names are mapped to their generic ingredient inside the Medication Safety Check, so typing the name on your bottle works.
Usually not. Most entries here call for one of three things: separating the doses by a few hours, monitoring a lab value or a home reading for a couple of weeks, or a prescriber-led dose adjustment. The decision belongs to the clinician who manages the prescription — what this page is for is making sure the conversation happens before you start rather than after something goes wrong.