Drug & supplement interaction

Garlic + Warfarin Sodium

Warfarin Sodium brand names: Coumadin, Panwarfin, Sofarin.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Warfarin Sodium falls into 3 drug categories that Garlic can interact with; the most serious is rated moderate. Theoretically, garlic products containing allicin might induce intestinal CYP3A4 and inhibit hepatic CYP3A4.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Garlic and Warfarin Sodium

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Garlic interacts with whole categories of medication. Warfarin Sodium falls into 3 of those categories, so it can interact with Garlic in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 3

Why this applies to Warfarin Sodium

Warfarin Sodium falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Garlic interacts with.

Theoretically, garlic products containing allicin might induce intestinal CYP3A4 and inhibit hepatic CYP3A4. This may increase or decrease levels of drugs metabolized by CYP3A4.
Some human research suggests that garlic may induce INTESTINAL CYP3A4, reducing levels of drugs metabolized by this enzyme. This is primarily based on a study showing that taking a specific allicin-containing garlic product (GarliPure Maximum Allicin Formula, Natrol Inc.) twice daily for 3 days reduces saquinavir levels by approximately 50%. It is speculated that the allicin constituent induced CYP3A4 in the gut mucosa. Another study shows that giving docetaxel intravenously, bypassing the CYP3A4 enzymes in the gut mucosa, along with the same specific garlic product for 12 consecutive days, does not affect docetaxel levels. Conversely, there is concern that garlic may inhibit HEPATIC CYP3A4. In a single case report, increased tacrolimus levels and liver injury occurred in a liver transplant patient after taking a specific garlic supplement (Garlicin Cardio, Nature's Way) at up to three times the manufacturer recommended dose for 7 days. Several other studies have evaluated the impact of other garlic formulations on CYP3A4 substrates and have found no effect. Most of the products in these studies provided little or no allicin.
Severity Moderate Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture with warfarin and garlic. The CYP3A4 enzyme effect you may have read about is pretty minor for warfarin, since warfarin is mostly cleared by a different enzyme (CYP2C9). The bigger concern is simpler: concentrated garlic supplements can have a mild blood-thinning effect of their own. Stack that on top of warfarin and you may nudge your bleeding risk up, think easy bruising, nosebleeds, bleeding gums, or blood in the urine or stool.

Warfarin is one of those drugs where small shifts matter, so your INR is the thing to watch. Garlic used in cooking is very unlikely to cause trouble, but talk to your pharmacist or doctor before starting a garlic supplement so they can keep an eye on your numbers.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Piscitelli SC, Burstein AH, Welden N, et al. The effect of garlic supplements on the pharmacokinetics of saquinavir. Clin Infect Dis 2002;34:234-8. PubMed
  2. Markowitz JS, Devane CL, Chavin KD, et al. Effects of garlic (Allium sativum L.) supplementation on cytochrome P450 2D6 and 3A4 activity in healthy volunteers. Clin Pharmacol Ther 2003;74:170-7.. PubMed
  3. Gurley BJ, Gardner SF, Hubbard MA, et al. Cytochrome P450 phenotypic ratios for predicting herb-drug interactions in humans. Clin Pharmacol Ther 2002;72:276-87.. PubMed
  4. Dhamija P, Malhotra S, Pandhi P. Effect of oral administration of crude aqueous extract of garlic on pharmacokinetic parameters of isoniazid and rifampicin in rabbits. Pharmacology 2006;77:100-4. PubMed
  5. Cox MC, Low J, Lee J, et al. Influence of garlic (Allium sativum) on the pharmacokinetics of docetaxel. Clin Cancer Res 2006;12:4636-40.
  6. Jalloh MA, Gregory PJ, Hein D, et al. Dietary supplement interactions with antiretrovirals: a systematic review. Int J STD AIDS. 2017 Jan;28(1):4-15. PubMed
  7. Gallicano K, Foster B, Choudhri S. Effect of short-term administration of garlic supplements on single-dose ritonavir pharmacokinetics in healthy volunteers. Br J Clin Pharmacol. 2003;55(2):199-202. PubMed
  8. Shaikh SA, Tischer S, Choi EK, Fontana RJ. Good for the lung but bad for the liver? Garlic-induced hepatotoxicity following liver transplantation. J Clin Pharm Ther. 2017;42(5):646-648. PubMed
Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

2 of 3

Warfarin Sodium also falls under ANTICOAGULANT/ANTIPLATELET DRUGS.

Garlic may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Raw garlic and a variety of garlic extracts have antiplatelet activity and can increase prothrombin time.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the deal with garlic and warfarin. Warfarin already slows down your blood's ability to clot, and that effect has to be kept in a fairly narrow window. Garlic supplements can have their own mild blood-thinning (antiplatelet) action, so stacking the two together could nudge you toward easier bleeding. In real life that might look like more bruising, nosebleeds, bleeding gums, or blood that takes longer to stop from a small cut.

I'll be honest, this concern is mostly theoretical and based on how the two work, not strong human studies. Garlic used in cooking is very unlikely to matter. Concentrated supplements are where I'd pay attention. Don't change anything on your own. Just check with your pharmacist or doctor first, since your INR may need a look.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Rose KD, Croissant PD, Parliament CF, Levin MB. Spontaneous spinal epidural hematoma with associated platelet dysfunction from excessive garlic ingestion: a case report. Neurosurg 1990;26:880-2. PubMed
  2. Sunter WH. Warfarin and garlic. Pharm J 1991;246:722.
  3. Steiner M, Lin RS. Changes in platelet function and susceptibility of lipoproteins to oxidation associated with administration of aged garlic extract. J Cardiovasc Pharmacol 1998;31:904-8. PubMed
  4. Rahman K, Billington D. Dietary supplementation with aged garlic extract inhibits ADP-induced platelet aggregation in humans. J Nutr 2000;130:2662-5. PubMed
  5. Steiner M, Li W. Aged garlic extract, a modulator of cardiovascular risk factors: a dose-finding study on the effects of AGE on platelet functions. J Nutr 2001;131:980S-4S. PubMed
  6. Kiesewetter H, Jung F, Jung EM, et al. Effect of garlic on platelet aggregation in patients with increased risk of juvenile ischaemic attack. Eur J Clin Pharmacol 1993;45:333-6. PubMed
  7. Legnani C, Frascaro M, Guazzaloca G, et al. Effects of a dried garlic preparation on fibrinolysis and platelet aggregation in healthy subjects. Arzneimittelforschung 1993;43:119-22.
  8. Gadkari JV, Joshi VD. Effect of ingestion of raw garlic on serum cholesterol level, clotting time and fibrinolytic activity in normal subjects. J Postgrad.Med 1991;37:128-131.
  9. Woodbury A, Sniecinski R. Garlic-induced surgical bleeding: How much is too much? A Case Rep. 2016;7(12):266-269. PubMed
Moderate

WARFARIN (Coumadin)

3 of 3
Theoretically, garlic might increase the risk of bleeding with warfarin.
Raw garlic and a variety of garlic extracts have antiplatelet activity and can increase prothrombin time. In addition, there is a report of two patients who experienced an increase in a previously stabilized international normalized ratio (INR) with concomitant garlic and warfarin use. However, this report has been subsequently debated due to limited clinical information. Other clinical studies have not identified an effect of garlic on INR, warfarin pharmacokinetics, or bleeding risk. More evidence is needed to determine the safety of using garlic with warfarin.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: warfarin (Coumadin) is a finicky blood thinner where small shifts can matter, so any added bleeding risk gets our attention. Concentrated garlic supplements can make your platelets a little less sticky on their own, and in theory that could nudge you toward easier bleeding when stacked on top of warfarin. There's even an old report of two people whose INR climbed, though that case was shaky and most studies since haven't found a real effect on INR or bleeding.

So the evidence here is thin and mostly anecdotal. Garlic in your cooking is very unlikely to cause trouble. If you're thinking about garlic pills or extracts, please run it past your pharmacist or doctor first, and watch for things like unusual bruising, nosebleeds, or bleeding gums.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Rose KD, Croissant PD, Parliament CF, Levin MB. Spontaneous spinal epidural hematoma with associated platelet dysfunction from excessive garlic ingestion: a case report. Neurosurg 1990;26:880-2. PubMed
  2. Sunter WH. Warfarin and garlic. Pharm J 1991;246:722.
  3. Steiner M, Lin RS. Changes in platelet function and susceptibility of lipoproteins to oxidation associated with administration of aged garlic extract. J Cardiovasc Pharmacol 1998;31:904-8. PubMed
  4. Rahman K, Billington D. Dietary supplementation with aged garlic extract inhibits ADP-induced platelet aggregation in humans. J Nutr 2000;130:2662-5. PubMed
  5. Steiner M, Li W. Aged garlic extract, a modulator of cardiovascular risk factors: a dose-finding study on the effects of AGE on platelet functions. J Nutr 2001;131:980S-4S. PubMed
  6. Kiesewetter H, Jung F, Jung EM, et al. Effect of garlic on platelet aggregation in patients with increased risk of juvenile ischaemic attack. Eur J Clin Pharmacol 1993;45:333-6. PubMed
  7. Legnani C, Frascaro M, Guazzaloca G, et al. Effects of a dried garlic preparation on fibrinolysis and platelet aggregation in healthy subjects. Arzneimittelforschung 1993;43:119-22.
  8. Macan H, Uykimpang R, Alconcel M, et al. Aged garlic extract may be safe for patients on warfarin therapy. J Nutr 2006;136(3 Suppl):793S-795S. PubMed
  9. Mohammed Abdul MI, Jiang X, Williams KM, et al. Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects. Br J Pharmacol 2008;154:1691-700. PubMed
  10. Vaes, L. P. and Chyka, P. A. Interactions of warfarin with garlic, ginger, ginkgo, or ginseng: nature of the evidence. Ann Pharmacother 2000;34(12):1478-1482. PubMed
  11. Gadkari JV, Joshi VD. Effect of ingestion of raw garlic on serum cholesterol level, clotting time and fibrinolytic activity in normal subjects. J Postgrad.Med 1991;37:128-131.
  12. Sunter WH. Warfarin and garlic. Pharm J 1991;246:722.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Garlic Also Interacts With Other Medications

Garlic has 988 moderate known drug interactions in our database — the Warfarin Sodium one above is among them. If you take anything else, check it against the full list below.

Moderate 988 No known interaction 1,842 (incl. Warfarin Sodium)
Taking anything else?

Check Another of Your Medications Against Garlic

Covers the 2,830 medications we’ve checked against Garlic. Pick one to open its full report.

From our Q&A

Questions About Garlic or Warfarin Sodium

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Garlic or Warfarin Sodium, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Warfarin Sodium

This page covers Garlic only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Warfarin Sodium page lists 361 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Alfalfa (major), American Ginseng (major), Beer (major) and Cannabis (major).

Open the Warfarin Sodium interaction page

One more smart check

Taking Garlic as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,118 real supplement products containing Garlic, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Garlic. Your product may carry other ingredients that interact with Warfarin Sodium too, on top of Garlic — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Garlic and Warfarin Sodium Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Garlic
Top 5%

#58 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Warfarin Sodium
Top 1%

#20 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Garlic

What is Garlic?

Garlic
  • High blood pressure
  • High cholesterol
  • Heart health
  • Immune support and common cold
  • Antimicrobial uses

Garlic is a common food and supplement that may modestly help with blood pressure and cholesterol, though the evidence is mixed and effects are usually small. It is generally safe in food amounts, but concentrated supplements can cause stomach upset, breath and body odor, and a higher risk of bleeding. Talk with your pharmacist or doctor before taking garlic supplements, especially if you take other medicines.

Read the full Garlic monograph & all interactions
Medication

About Warfarin

What Is Warfarin Used For?

Brand names: Coumadin, Panwarfin, Sofarin

Warfarin sodium tablets and Jantoven tablets are both used to prevent and treat venous thrombosis (blood clots in the veins) and pulmonary embolism (a clot in the lungs). They are also used to prevent clot-related complications in people with atrial fibrillation (an irregular heart rhythm) or who have had a heart valve replaced.

In people who have had a heart attack, warfarin is used to reduce the risk of death, another heart attack, stroke, or other clotting events. It does not dissolve an existing clot, but it helps prevent the clot from growing and stops new dangerous clots from forming.

See full Warfarin drug information
Keep checking

Other Drugs & Garlic

Browse every other medication we’ve checked against Garlic — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
988Moderate
0Minor
1,841No known interaction
988 Moderate 1,841 No interaction
Moderate

988 interactions

Showing 60 of 988 moderate interactions — see all 988 on the Garlic page.

No interaction 1,841 drugs checked — show the list

We also checked Garlic against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,841 medications checked with no known interaction — see the full Garlic list.

See the full Garlic interactions page
See every supplement checked against Warfarin Sodium, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Garlic monograph › Uses, safety, and every drug interaction in one place Warfarin Sodium supplement interactions › Every supplement checked against Warfarin Sodium, ranked by severity Warfarin drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Garlic and Warfarin Sodium Together: Common Questions

Can you take Garlic with Warfarin Sodium?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 3 interactions listed for Garlic and Warfarin Sodium?
Warfarin Sodium belongs to more than one drug category, and Garlic interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Garlic and Warfarin Sodium interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Warfarin Sodium and Garlic?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.