Herb & supplement monograph

Garlic Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Garlic interacts with medications. The heart of this page is the interaction list — every drug Garlic is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Garlic is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Garlic Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Garlic drug interaction appears low for most people. None of garlic's listed interactions are rated major, and nearly all rest on lab, animal, or limited human evidence rather than well-controlled human studies.

Interactions deserving the most attention

The pairings that deserve the most care involve bleeding, blood sugar, and drug levels. Garlic has antiplatelet activity and may add to the effect of warfarin and other blood thinners, and human research shows it can lower blood glucose, which matters for people taking diabetes medications. Human studies also suggest allicin-containing garlic products may reduce levels of HIV protease inhibitors such as saquinavir, and a case report links a garlic supplement to raised levels of the transplant drug tacrolimus.

What the rest of the list means

The long list of interacting medications mostly reflects one prediction: garlic may affect enzymes the body uses to clear many different drugs. Because of that, hundreds of medications are flagged even though most of these pairings are theoretical, and some predicted effects have not held up when tested in people. A flagged combination is a reason for awareness, not proof of harm.

Check your medications against Garlic

Based on HelloPharmacist’s Garlic interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Garlic

991 medications have a known interaction with Garlic, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Garlic using our pharmacist-reviewed interaction data.

AI summaries are generated from our Garlic interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Garlic combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Garlic affects

Every type of medication (drug category) Garlic is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 12 drug categories Garlic interacts with

Anticoagulant/antiplatelet DrugsAntidiabetes DrugsAntihypertensive DrugsAtazanavir (reyataz)Cytochrome P450 2e1 (cyp2e1) SubstratesCytochrome P450 3a4 (cyp3a4) SubstratesIsoniazidProtease Inhibitors (pis)Saquinavir (fortovase, Invirase)Sofosbuvir (sovaldi)Tacrolimus (prograf)Warfarin (coumadin)

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.

Likelihood Possible Evidence D

Antidiabetes Drugs

Theoretically, taking garlic with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical research suggests that garlic and garlic extract lower blood glucose levels in healthy and diabetic individuals.

Likelihood Possible Evidence B

Antihypertensive Drugs

Theoretically, taking garlic with antihypertensive drugs might increase the risk of hypotension.
In human research, both garlic and garlic extracts have blood pressure-lowering effects.

Likelihood Possible Evidence D

Atazanavir (Reyataz)

Theoretically, garlic might decrease levels and effects of atazanavir.
In a case report, a patient consuming six stir-fried garlic cloves three times weekly developed suboptimal atazanavir levels and increases in HIV viral load. While the exact cause of this interaction is unclear, there is speculation that garlic might decrease the intestinal absorption of atazanavir or increase its metabolism by inducing cytochrome P450 3A4 (CYP3A4). Until more is known, advise patients not to consume large amounts of garlic while taking atazanavir.

Likelihood Possible Evidence D

Cytochrome P450 2E1 (Cyp2E1) Substrates

Garlic might increase levels of drugs metabolized by CYP2E1.
Clinical research suggests garlic oil can inhibit the activity of CYP2E1 by 39%. Use garlic oil cautiously in patients taking drugs metabolized by these enzymes.

Likelihood Probable Evidence B

Cytochrome P450 3A4 (Cyp3A4) Substrates

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.

Likelihood Possible Evidence B

Isoniazid

Theoretically, garlic might decrease levels of isoniazid.
Animal research suggests that an aqueous extract of garlic reduces isoniazid levels by about 65%. Garlic reduced the maximum concentration (Cmax) and area under the curve (AUC), but not the half-life, of isoniazid. This suggests that garlic extract might inhibit isoniazid absorption across the intestinal mucosa; however, the exact mechanism of this potential interaction is not known.

Likelihood Possible Evidence D

Protease Inhibitors (Pis)

Theoretically, garlic products containing allicin might decrease levels of PIs.
Protease inhibitors are metabolized by cytochrome P450 3A4 (CYP3A4) isoenzymes. There is concern that garlic products containing allicin might induce intestinal CYP3A4, reducing plasma levels of protease inhibitors. This is primarily based on a study showing that taking a specific garlic product (GarliPure Maximum Allicin Formula, Natrol Inc.) twice daily for 3 days reduces levels of saquinavir, a PI, by approximately 50%. It is speculated that the allicin constituent induce CYP3A4 in the gut mucosa. Several 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.

Likelihood Possible Evidence B

Saquinavir (Fortovase, Invirase)

Theoretically, garlic containing allicin might decrease levels of saquinavir.
Saquinavir is a substrate of cytochrome P450 3A4 (CYP3A4) isoenzymes. There is concern that garlic products containing allicin might induce intestinal CYP3A4 and cause subtherapeutic levels of saquinavir. This is primarily based on a pharmacokinetic study showing that taking a specific 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 induces CYP3A4 in the gut mucosa. Several pharmacokinetic 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. Until more is known about this potential interaction, use garlic containing allicin cautiously in patients taking saquinavir.

Likelihood Possible Evidence B

Sofosbuvir (Sovaldi)

Theoretically, taking garlic with sofosbuvir might decrease its effectiveness.
Animal research in rats shows that giving aged garlic extract 120 mg/kg orally daily for 14 days decreases the area under the concentration time curve (AUC) after a single sofosbuvir dose of 40 mg/kg by 36%, increases the clearance by 63%, and decreases the plasma concentrations at 1 and 8 hours by 35% and 58%, respectively. This interaction is hypothesized to be due to induction of intestinal P-glycoprotein expression by garlic.

Likelihood Possible Evidence D

Tacrolimus (Prograf)

Theoretically, garlic might increase levels of tacrolimus.
In one case report, a liver transplant patient taking tacrolimus experienced increased tacrolimus levels and liver injury after taking a specific garlic supplement (Garlicin Cardio, Nature's Way) at up to three times the manufacturer recommended dose for 7 days. It is speculated that garlic inhibited hepatic cytochrome P450 3A4 (CYP3A4), which increased plasma levels of tacrolimus.

Likelihood Possible Evidence B

Warfarin (Coumadin)

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.

Likelihood Possible Evidence D

Monograph

Garlic: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

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.

Scientific name: Allium sativum
Family: Amaryllidaceae
Part used: Bulb (cloves)
Common forms: Fresh cloves, powder, capsules, tablets, softgels, aged garlic extract, garlic oil

People commonly use it for

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

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally safe as food, but supplements may cause stomach upset and increase bleeding risk.

PregnancyLikely Safe

When used orally in amounts commonly found in foods.

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in amounts commonly found in foods.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Garlic (Allium sativum) is a pungent bulb in the onion family. It is native to central Asia but is now grown all over the world. People have used it as a food and a folk remedy for thousands of years.

Besides cooking, garlic is taken as a supplement for heart and circulation health, cholesterol, and as a general immune booster. It comes in many forms, including fresh cloves, dried powder, capsules, oils, and aged garlic extract, which is made by soaking sliced garlic in alcohol over many months.

How it works

When garlic is crushed or chopped, it releases a compound called alliin, which an enzyme quickly turns into allicin. Allicin and other sulfur-containing compounds are thought to be responsible for many of garlic's effects and its strong smell.

Researchers believe these compounds may help relax blood vessels, support healthy cholesterol levels, and act against certain microbes. Garlic compounds may also affect how blood platelets clump together, which is why garlic can thin the blood slightly.

Much of this work comes from laboratory and animal studies, so it does not always translate into clear benefits in people.

Effectiveness

Does Garlic work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 70 uses evaluated

6 Possibly effective 2 Leans ineffective 62 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Effective Atherosclerosis