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Food and medicine interaction

Garlic supplements and warfarin and other anticoagulants, aspirin and antiplatelet drugs

ProbableEvidence level: probable. Case reports in people plus a known mechanism, but no controlled studies.

Last reviewed

What can happen

Garlic supplements may increase the risk of bleeding, which matters when combined with drugs that also affect bleeding or before surgery. In a small trial, aged garlic extract did not increase bleeding in closely monitored warfarin patients.

Why it happens
Garlic compounds can reduce platelet clumping; case reports and reviews link garlic with over-anticoagulation on warfarin.
At ordinary food amounts
NCCIH's caution is about supplements. Garlic used in cooking is not the concern in the studies cited.

What to do

Tell your prescriber and surgical team about garlic supplements, especially before an operation. Keep any change in garlic supplement use under your anticoagulation clinic's watch.

Never stop or change a prescribed medicine without talking to the prescriber.

Common questions

Can I have garlic supplements while taking anticoagulants?

Tell your prescriber and surgical team about garlic supplements, especially before an operation. Keep any change in garlic supplement use under your anticoagulation clinic's watch. NCCIH's caution is about supplements. Garlic used in cooking is not the concern in the studies cited.

Sources

  1. National Center for Complementary and Integrative Health. Garlic: Usefulness and Safety.
  2. Macan H, et al. Aged garlic extract may be safe for patients on warfarin therapy. J Nutr. 2006. PMID 16484565.
  3. Izzo AA, et al. Cardiovascular pharmacotherapy and herbal medicines: the risk of drug interaction. Int J Cardiol. 2005. PMID 15676159.

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