Drug class·Blood Thinners·Reviewed June 9, 2026
Blood thinners and supplements: the highest-stakes category.
Anticoagulants and antiplatelets are where supplement interactions get genuinely dangerous: vitamin K directly opposes warfarin, and a long list of common supplements (fish oil, ginkgo, garlic, nattokinase) add their own antiplatelet effect on top. Warfarin and the DOACs also behave very differently, so check your exact medication.
Blood Thinners at a glance.
A quick, data-grounded summary. The per-drug tables are below.
Across the 8 blood thinners in the NutriStack database (Warfarin, Aspirin Low-Dose, Apixaban, Clopidogrel, and Rivaroxaban and 3 more), 41 substances have a documented interaction, 7 of them flagged to avoid or as a serious conflict. Interactions are documented per drug, and members of a class do not all behave the same, so check your exact medication below. None of this replaces your prescriber's advice.
The blood thinners we track.
Open any medication for its own full interaction and depletion guide.
Substances that interact with blood thinners.
Merged across the class, highest severity first. The 'Documented for' column shows which members carry the interaction record; an absent drug means no documented record, not proven safety.
| Substance | Interaction | Documented for | What happens |
|---|---|---|---|
| St. John's Wort | Contraindicated | Warfarin, Apixaban, Clopidogrel +3 more | Warfarin: St. John's Wort is a potent inducer of CYP3A4, CYP2C9, and P-glycoprotein, which dramatically accelerates warfarin metabolism and reduces... |
| Chlorella | Conflict | Warfarin | Chlorella is high in vitamin K, which antagonizes warfarin's anticoagulant effect. Case report: thrombotest values exceeded therapeutic... |
| Green Tea Extract | Conflict | Warfarin | Green tea contains vitamin K1 which can antagonize warfarin's anticoagulant effect. Concentrated green tea extract supplements provide... |
| Vitamin C Liposomal | Conflict | Warfarin | High-dose vitamin C has rare case-report evidence of reducing warfarin response, followed by rapid INR increases after vitamin C is... |
| Vitamin K1 | Conflict | Warfarin | Vitamin K1 (phytonadione) directly reverses warfarin's anticoagulant effect. Even small, regular doses found in multivitamins (25 mcg/day)... |
| Vitamin K2 | Conflict | Warfarin | Vitamin K2 directly opposes warfarin's mechanism of action. Warfarin works by inhibiting vitamin K-dependent clotting factor synthesis, so... |
| Vitamin K2 MK-4 | Conflict | Warfarin | Vitamin K2 in the MK-4 (menatetrenone) form opposes warfarin in the same way as K1 and K2 MK-7: it restores production of vitamin... |
| Fish Oil | Caution | All 8 blood thinners | Warfarin: Fish oil may potentiate warfarin's anticoagulant effect through its own antiplatelet and antithrombotic properties. While moderate doses... |
| Garlic Extract | Caution | All 8 blood thinners | Warfarin: Garlic supplements possess antiplatelet properties that may increase bleeding risk when combined with warfarin. Several case reports have... |
| Ginkgo Biloba | Caution | All 8 blood thinners | Warfarin: Ginkgo biloba has significant antiplatelet activity that increases bleeding risk when combined with warfarin. Multiple case reports... |
| Nattokinase | Caution | All 8 blood thinners | Warfarin: Nattokinase is a fibrinolytic enzyme that degrades fibrin directly and reduces clotting factors. Combined with warfarin, the additive... |
| Turmeric/Curcumin | Caution | Warfarin, Aspirin Low-Dose, Apixaban +2 more | Warfarin: Curcumin may inhibit platelet aggregation and has shown anticoagulant properties in vitro and in animal studies. When combined with... |
| Ginger Extract | Caution | Warfarin, Aspirin Low-Dose, Clopidogrel | Warfarin: Ginger extract inhibits platelet aggregation via thromboxane synthase suppression and may potentiate warfarin. Case reports describe... |
| Bromelain | Caution | Warfarin, Aspirin Low-Dose | Warfarin: Bromelain, a proteolytic enzyme from pineapple stem, inhibits platelet aggregation and has been shown to reduce thrombin-, ADP-, and... |
| Ibuprofen | Caution | Warfarin, Apixaban | Warfarin: NSAIDs increase bleeding risk with warfarin through dual mechanisms: antiplatelet effects and GI mucosal damage. Ibuprofen also inhibits... |
| Krill Oil | Caution | Warfarin, Aspirin Low-Dose | Warfarin: Krill oil contains the same omega-3 fatty acids (EPA and DHA) as fish oil, which reduce platelet thromboxane A2 and may prolong bleeding... |
| Quercetin | Caution | Warfarin, Apixaban | Warfarin: Quercetin and its metabolites strongly displace warfarin from human serum albumin, which can transiently raise free (active) warfarin... |
| Vitamin E | Caution | Warfarin, Aspirin Low-Dose | Warfarin: High-dose vitamin E may potentiate warfarin's anticoagulant effect and increase bleeding risk. Vitamin E at high supplemental doses can... |
| Warfarin | Caution | Aspirin Low-Dose, Clopidogrel | Aspirin Low-Dose: Concurrent anticoagulant and antiplatelet therapy significantly increases bleeding risk. While sometimes used intentionally (e.g.,... |
| Alcohol | Caution | Aspirin Low-Dose | Alcohol increases the risk of upper gastrointestinal bleeding from low-dose aspirin. Aspirin impairs platelet function and weakens gastric... |
| Aspirin Low-Dose | Caution | Warfarin | Concurrent anticoagulant and antiplatelet therapy significantly increases bleeding risk. While sometimes used intentionally (e.g.,... |
| Bee Pollen | Caution | Warfarin | Bee pollen has case-report evidence of potentiating warfarin. A stable warfarin patient developed an INR of 7.1 about one month after... |
| Berberine HCl | Caution | Warfarin | Berberine displaces warfarin from plasma protein binding sites and inhibits CYP2C9 (warfarin metabolism enzyme). May alter INR... |
| Black Seed Oil | Caution | Warfarin | Thymoquinone, the main bioactive in black seed oil (Nigella sativa), is a competitive inhibitor of CYP2C9-mediated warfarin... |
| Boswellia | Caution | Warfarin | Boswellia serrata extracts inhibit CYP2C9, CYP3A4, and CYP2C19, the isoenzymes responsible for warfarin metabolism. Spontaneous... |
| Cannabis (THC-Dominant) | Caution | Warfarin | THC-dominant cannabis can raise INR and bleeding risk in people taking warfarin. Case reports describe supratherapeutic INR after... |
| Chondroitin | Caution | Warfarin | Chondroitin is structurally a heparan-like sulfated glycosaminoglycan and is commonly taken with glucosamine for joint pain. Combined... |
| Clopidogrel | Caution | Warfarin | Triple therapy (warfarin + clopidogrel + aspirin) or dual therapy (warfarin + clopidogrel) substantially increases major bleeding risk... |
| Coenzyme Q10 | Caution | Warfarin | Coenzyme Q10 (ubiquinone) is structurally similar to vitamin K and may reduce warfarin's anticoagulant effect in some patients. Case... |
| Coenzyme Q10 Ubiquinol | Caution | Warfarin | CoQ10 is structurally similar to vitamin K2 (both are quinones) and may partially reduce warfarin's anticoagulant effect. Several case... |
| Curcumin Phytosome | Caution | Aspirin Low-Dose | Curcumin phytosome products may produce higher systemic curcumin exposure than standard turmeric powders and may add antiplatelet effects... |
| Evening Primrose Oil | Caution | Warfarin | Evening primrose oil is rich in gamma-linolenic acid (GLA), which has documented antiplatelet activity and can prolong bleeding time.... |
| Fenugreek | Caution | Warfarin | Fenugreek aqueous extract inhibits coagulation in vitro and significantly prolongs prothrombin time. A well-documented case describes a... |
| Flaxseed Oil | Caution | Aspirin Low-Dose | Flaxseed oil supplies alpha-linolenic acid and may have mild antiplatelet or lipid-mediated vascular effects, but direct clinical bleeding... |
| Glucosamine | Caution | Warfarin | 21 spontaneous reports of increased INR with glucosamine use in WHO database. |
| Grape Seed Extract | Caution | Warfarin | Grape seed extract contains procyanidins that inhibit platelet aggregation and prolong APTT and PT in vitro. A case report describes a... |
| Lycopene | Caution | Aspirin Low-Dose | Lycopene has antiplatelet activity in platelet studies, and an in vitro human platelet study directly evaluated lycopene with aspirin and... |
| Pine Bark Extract | Caution | Warfarin | Pine bark extract (pycnogenol) inhibits platelet aggregation and reduces thromboxane generation. Combined with warfarin, these... |
| Resveratrol | Caution | Warfarin | Resveratrol inhibits CYP2C9, the main enzyme that clears the more potent S-enantiomer of warfarin, and also inhibits BCRP-mediated efflux.... |
| Royal Jelly | Caution | Warfarin | Royal Jelly has case-report evidence of potentiating warfarin. An elderly patient with previously stable warfarin therapy developed... |
| Saw Palmetto | Caution | Warfarin | Saw palmetto has been linked to coagulopathy and excessive surgical bleeding in case reports, including hematuria and intraoperative... |
Common blood thinners questions.
Quick answers drawn from the tables above.
What supplements should I avoid with blood thinners?
Across the class, 7 substance pairings are flagged to avoid or as a serious conflict, including St. John's Wort, Chlorella, Green Tea Extract, Vitamin C Liposomal, Vitamin K1, and Vitamin K2. The exact risk depends on which medication in the class you take, so check your specific drug's page and confirm with your prescriber.
Do all blood thinners interact with supplements the same way?
No. Interactions are documented per drug, and the 8 blood thinners in the database differ in how they are absorbed and cleared. The class table above shows which members carry each record; a drug without a record is undocumented, not proven safe.
Is it safe to take St. John's Wort with blood thinners?
NutriStack classifies the St. John's Wort and Warfarin pairing as contraindicated: St. John's Wort is a potent inducer of CYP3A4, CYP2C9, and P-glycoprotein, which dramatically accelerates warfarin metabolism and reduces its plasma levels. This can... The interaction is documented for 6 of the 8 blood thinners, and severity differs by drug. Always confirm with your prescriber.
Check your whole stack
See how your medication fits your supplements.
NutriStack screens your full routine for interactions and depletions, and updates the moment you change it.