NutriStack
Chlorella and Warfarin, a conflict.
Chlorella is high in vitamin K, which antagonizes warfarin's anticoagulant effect. Case report: thrombotest values exceeded therapeutic limit.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
Every entry follows the same shape: what is happening, the mechanism, the recommendation, and the primary literature.
At a glance
- Pair type
- Conflict
- Evidence (highest tier)
- Moderate
- Source citations
- 6 sources
- Stack Score effect
- −10 to your Stack Score (per scored conflict row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Conflict · Moderate evidence
Conflict
What is happening. Chlorella is high in vitamin K, which antagonizes warfarin's anticoagulant effect. Case report: thrombotest values exceeded therapeutic limit.
Mechanism. Vitamin K content opposes warfarin's inhibition of vitamin K-dependent clotting factors.
Recommendation. Avoid while on warfarin, or maintain very consistent intake with INR monitoring.
Sources (3)
- Chlorella warfarin interaction case report PMID 8777808
- Sanayei M, Izadi A, Hajizadeh-Sharafabad F et al.. Chlorella vulgaris in combination with high intensity interval training in overweight and obese women: a randomized double-blind clinical trial. Journal of Diabetes and Metabolic Disorders. 2021. PMID 34178863
- Wang M, Zeraatkar D, Obeda M, Lee M et al.. Drug-drug interactions with warfarin: A systematic review and meta-analysis. British Journal of Clinical Pharmacology. 2021. PMID 33769581
Conflict · Emerging evidence
Conflict
What is happening. Chlorella can contain substantial vitamin K and may reduce warfarin anticoagulant effect. A case report described loss of warfarin control after chlorella intake, which could raise clotting risk in patients using warfarin for stroke or clot prevention.
Mechanism. Warfarin inhibits vitamin K recycling to reduce vitamin K-dependent clotting factor activation. Vitamin K-rich chlorella can provide substrate that counteracts warfarin effect and lowers anticoagulation intensity.
Recommendation. Avoid starting or stopping chlorella while taking warfarin unless your anticoagulation clinic knows. If chlorella is used, keep intake consistent and check INR after any change.
Sources (3)
- Ohkawa S, Yoneda Y, Ohsumi Y, Tabuchi M. Warfarin therapy and chlorella. Rinsho Shinkeigaku. 1995;35(7):806-807. PMID 8777808
- Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary management of patients on warfarin. Nutrition Reviews. 1999;57(9):288-296. PMID 10568341
- Wang M, Zeraatkar D, Obeda M, et al. Drug-drug interactions with warfarin: A systematic review and meta-analysis. British Journal of Clinical Pharmacology. 2021;87(11):4051-4100. PMID 33769581
Stack Score
How this pair moves the number.
Effect on the composite score
If both Chlorella and Warfarin are in the same stack, this pair applies −10 to your Stack Score (per scored conflict row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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