What it is
Garlic is the bulb of Allium sativum. When it is crushed, the compound alliin is converted to allicin, which gives garlic its smell and is unstable. Supplements are made from dried garlic powder, aged garlic extract or garlic oil, and these forms contain different compounds.
What the research says
Cholesterol
ModerateIn people with high cholesterol, garlic supplements may lower total and LDL cholesterol to a small extent. This is the most-researched use.
Blood pressure
MixedLimited evidence suggests a slight lowering in people with high blood pressure.
Blood sugar
LimitedMay slightly reduce blood sugar in people with diabetes.
Colds
LimitedOnly two small, weak studies; not enough to say.
Amounts used in studies
Trials have commonly used 600–1,200 mg a day of dried garlic powder, or aged garlic extract, for 8–12 weeks. Studies of up to seven years have reported it safe.
Who should avoid it
- The week or two before surgery or dental extraction.
- Pregnancy and breastfeeding, in amounts above food.
- Garlic allergy.
Medicines to watch
- Blood thinners and aspirin: added bleeding risk.
- Some HIV medicines (such as saquinavir): garlic can lower their levels. Ask your clinic before using garlic supplements.
What to look for when buying
- Ask whether the powder is standardised for allicin potential (alliin content); unstandardised powder varies widely.
- Odour is normal. Enteric or coated capsules reduce garlic breath.
Common questions
Will it make my breath smell?
Some people notice it. Taking the capsule with a meal helps.
Can garlic replace my cholesterol medicine?
No. The effects are small. Never stop a prescribed medicine without your doctor.
Read next
Sources
Last reviewed 19 October 2026 by Spicewell editorial team. How we write our guides
This guide is general information, not medical advice. Speak to a doctor or pharmacist before starting any supplement, especially if you are pregnant, breastfeeding, under 18 or taking medication.