Garlic

Allium sativum · Aged garlic extract · Allicin

Snapshot

Indications	Contraindications
Elevated cholesterol¹ Hypertension² Blood glucose¹ Inflammatory markers^3–5 Oxidative stress markers^3–5 Hepatic steatosis⁶	Saquinavir or ritonavir therapy⁷ Hypersensitivity to garlic⁷ Planned surgery⁷

Garlic (Allium sativum) is a culinary bulb also taken as powder, oil, or aged extract, with activity attributed to allicin and related sulfur compounds formed when cloves are crushed⁸. Supplementation is used for cholesterol, blood pressure, and glucose in adults with unfavorable cardiometabolic risk³, likely via lipid synthesis inhibition, vasodilation, and antiplatelet activity. It is also taken for immune function and the common cold, where trials are few⁹.

Meta-analyses of randomized trials report small reductions in total cholesterol, low-density lipoprotein (LDL) cholesterol, and blood pressure³. A pooled analysis found no significant association between garlic supplements and cancer risk¹⁰. In a 2025 Drosophila model of Alzheimer's disease, aged garlic extract improved locomotor function and oxidative markers; no human trial has tested this. About three thousand products list garlic, as capsules, softgels, and tablets of powder, oil, or aged extract; see Form comparison.

The protease inhibitor caution rests on pharmacokinetics: garlic lowered saquinavir concentrations in healthy volunteers, risking therapeutic failure⁸. Bleeding is the other concern: the European Medicines Agency monograph lists caution with anticoagulant or antiplatelet therapy because garlic may lengthen bleeding times⁷.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

66 sources, 50 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources