[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Herbal products and dietary supplements](https://durgical.com/en/pharmacology/classes/herbal-products-and-dietary-supplements/) › Garlic

# Garlic

## Herbal products and dietary supplements?

Herbal products and dietary supplements

Allium sativum supplements, promoted for cholesterol and blood pressure. Modest lipid effects at best; they can add to bleeding risk.

Updated Nov 1, 2026

Also called: Allium sativum, Aged garlic extract

## Quick facts

**Group**
[Herbal products and dietary supplements](https://durgical.com/en/pharmacology/classes/herbal-products-and-dietary-supplements/)

**Target**
Platelets and cholesterol synthesis (allicin and related sulfur compounds)

**Used for**
Promoted for high cholesterol

**Key effects**
Breath and body odour · Abdominal pain

**Monitor**
INR and bleeding signs

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

Crushing garlic converts alliin into allicin and related organosulfur compounds. In laboratory studies these inhibit HMG-CoA reductase and act as antioxidants; in clinical studies garlic has antiplatelet effects, possibly by reducing thromboxane synthesis. The cholesterol and blood pressure effects in people are small.

- Alliin becomes allicin when garlic is crushed
- Organosulfur compounds reach the blood
- Antiplatelet effect; weak lipid lowering
- Bleeding risk adds up with anticoagulants

## Indications

- Promoted for high cholesterol: may modestly lower total and LDL cholesterol [Atherosclerosis and dyslipidaemia →](https://durgical.com/en/conditions/atherosclerosis-and-dyslipidaemia/)
- Promoted for high blood pressure: limited evidence of a small effect

## Adverse effects

### Common

- Breath and body odour
- Abdominal pain, gas and nausea
- Allergic reactions
- Skin burns when raw garlic is applied to the skin

### Serious (rare, important)

- Bleeding, especially with anticoagulants or around surgery

## Contraindications

- Supplement doses with anticoagulants or antiplatelets without supervision
- Before surgery
- Supplement doses (more than in food) in pregnancy

## Key interactions

**Warfarin and other anticoagulants**
Higher bleeding risk

**Acetylsalicylic acid and other antiplatelets**
Additive antiplatelet effect

## What is monitored

- INR and bleeding signs in patients on warfarin
- Lipid profile if used for cholesterol

## Pregnancy and breastfeeding

Garlic as food is fine, but amounts larger than those in food may not be safe in pregnancy.

## Nursing care

- Ask every patient about herbal products and supplements and record them with the medicine list
- Ask about garlic supplements before surgery and in patients on anticoagulants
- Teach that «natural» does not mean safe and that supplements are not approved as medicines before sale

## Pharmacokinetics

**Absorption**
Taken by mouth as fresh garlic, dried powder or aged extract; enteric coating protects the enzyme that makes allicin

## Memory aid

Garlic: «Good for pasta, Gentle on LDL, Grim with warfarin».

## Test yourself

Think of the answer, then tap the question to see it.

## Which compound forms when garlic is crushed?

Allicin, from alliin.

## What is the best-supported effect of garlic supplements?

A modest fall in total and LDL cholesterol in people with high cholesterol.

## Why is a garlic supplement relevant before surgery?

It may increase bleeding risk, especially with anticoagulants or aspirin.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/garlic/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 2

- [Warfarin](https://durgical.com/en/pharmacology/warfarin/)
- [Atorvastatin](https://durgical.com/en/pharmacology/atorvastatin/)

## Related conditions 1

- [Atherosclerosis and dyslipidaemia](https://durgical.com/en/conditions/atherosclerosis-and-dyslipidaemia/)

[← Back to the class: Herbal products and dietary supplements](https://durgical.com/en/pharmacology/classes/herbal-products-and-dietary-supplements/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Garlic: Usefulness and Safety](https://www.nccih.nih.gov/health/garlic) (National Center for Complementary and Integrative Health (NCCIH), 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/garlic/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/garlic/