Cloves and Bleeding Risk with Anticoagulants
Yes, cloves should be discontinued at least 2 weeks before surgery and avoided in patients on anticoagulant therapy due to their antiplatelet effects and potential to increase bleeding risk.
Evidence-Based Recommendation
The most authoritative guidance comes from the 2021 Society for Perioperative Assessment and Quality Improvement (SPAQI) consensus statement, which explicitly addresses clove supplementation 1. While this guideline focuses on perioperative management, the underlying mechanism—inhibition of platelet aggregation—applies equally to patients on chronic anticoagulation.
Mechanism of Bleeding Risk
Cloves increase bleeding risk through antiplatelet activity rather than direct anticoagulant potentiation. This means:
- PT-INR levels may remain unchanged in warfarin patients, making the bleeding risk harder to detect through routine monitoring 2
- The antiplatelet effect adds to the anticoagulant effect, creating a cumulative bleeding risk
- This interaction has been documented in multiple reviews of herb-warfarin interactions 3, 4
Clinical Application
For patients on anticoagulants:
- Discontinue cloves immediately if currently being used as a supplement
- Avoid clove-containing herbal preparations entirely during anticoagulation therapy
- Question patients specifically about clove use, as patients often don't volunteer information about herbal supplements 3
- Monitor for bleeding signs even with normal INR values, since antiplatelet effects won't alter coagulation studies
Important Caveats
The evidence base consists primarily of:
- Theoretical risk based on known antiplatelet mechanisms
- Case reports and in vitro data 3
- Expert consensus rather than randomized trials 1
However, the absence of high-quality trial data should not be interpreted as safety. Given the narrow therapeutic window of anticoagulants and the serious consequences of bleeding (20.7% mortality in anticoagulant-associated bleeding events 5), the precautionary principle strongly favors avoidance.
Common Pitfall
Do not assume culinary use of cloves poses the same risk. The SPAQI guidelines address concentrated clove supplements and extracts. Small amounts used in cooking are unlikely to cause clinically significant antiplatelet effects, though this has not been formally studied.
The recommendation to hold cloves for 2 weeks perioperatively 1 reflects the time needed for platelet turnover and restoration of normal hemostatic function after antiplatelet exposure.