NutriStack
Black Seed Oil and Warfarin, a caution.
Thymoquinone, the main bioactive in black seed oil (Nigella sativa), is a competitive inhibitor of CYP2C9-mediated warfarin 7-hydroxylation. Pharmacokinetic modeling predicts that thymoquinone intakes above ~18 mg/day, or black seed oil above ~1 g/day, can meaningfully reduce warfarin clearance and raise INR.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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At a glance
- Substances
- Black Seed Oil and Warfarin
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Emerging evidence
Caution
What is happening. Thymoquinone, the main bioactive in black seed oil (Nigella sativa), is a competitive inhibitor of CYP2C9-mediated warfarin 7-hydroxylation. Pharmacokinetic modeling predicts that thymoquinone intakes above ~18 mg/day, or black seed oil above ~1 g/day, can meaningfully reduce warfarin clearance and raise INR.
Mechanism. Thymoquinone competitively inhibits CYP2C9 (Ki ~3.5 µM), the primary enzyme metabolising the more potent S-enantiomer of warfarin. Reduced clearance raises plasma S-warfarin and INR.
Recommendation. Avoid black seed oil supplements while on warfarin. Culinary use of small amounts of seeds is unlikely to matter. If you take a supplement, tell your anticoagulation clinic and ask for an INR check within 1-2 weeks.
Sources (2)
- Wang Z, Wang Z, Wang X, et al. Potential food-drug interaction risk of thymoquinone with warfarin. Chem Biol Interact. 2022;365:110070. PMID 35921950
- Tan CSS, Lee SWH. Warfarin and food, herbal or dietary supplement interactions: A systematic review. Br J Clin Pharmacol. 2021;87(2):352-374. PMID 32478963
Stack Score
How this pair moves the number.
Effect on the composite score
If both Black Seed Oil and Warfarin are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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