Garlic
Garlic: what NIH says about cholesterol, blood pressure, blood sugar and immune claims, bleeding risk before surgery, and skin burns from raw garlic.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
Do not put raw garlic on your skin. Fresh raw garlic may not be safe topically and can cause severe skin irritation and chemical burns. [1]
Overview
Garlic is grown worldwide and has a long history in food and health. Ancient writings from Egypt, Greece and India describe use for headache, pneumonia, throat conditions and stomach problems. Today it is promoted as a supplement to help manage cholesterol, blood pressure and diabetes, to prevent cancers and to boost immunity. [1]Names and parts
Allium sativum, bulb. [1][2] NIH says a great deal of research has been done, especially on cholesterol. [1] Studies mostly use supplements, which differ from cooking with garlic.What the research shows (NIH summary)
| Use | What NIH says | Strength of evidence |
|---|---|---|
| High cholesterol | Supplements may reduce total and LDL cholesterol to a small extent in people with high cholesterol. [1] | Small effect |
| High blood pressure | Limited evidence of a small reduction. [1] | Limited |
| Diabetes | Supplements may reduce blood sugar to a small extent. [1] | Small effect |
| Cancer | Eating garlic does not seem to reduce stomach cancer risk; colorectal cancer is uncertain. [1] | Uncertain |
| Immune boosting | Very little research; a 2022 review found only two small studies with weaknesses. [1] | Weak |
Safety
- Oral garlic has been used safely in studies lasting up to 7 years. Side effects: breath and body odor, abdominal pain, flatulence and nausea. Some people are allergic. [1]
- Bleeding: garlic supplements may increase the risk of bleeding. Tell your providers, especially before surgery or if you take anticoagulants or aspirin. [1]
- Garlic taken orally in amounts greater than food amounts may not be safe in pregnancy or breastfeeding. [1]
Frequently asked questions
Does garlic lower cholesterol?
NIH says supplements may reduce cholesterol to a small extent in people with high cholesterol. [1]
Should I stop garlic before surgery?
NIH says to tell your health care providers about garlic supplements, because they may increase bleeding risk. [1]
References
- National Center for Complementary and Integrative Health (NIH). Garlic: Usefulness and Safety. Page last updated February 2025.
- GBIF Secretariat. GBIF Backbone Taxonomy. Names checked 2026-10-22 through the GBIF species match service.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.