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Garlic (Allium sativum) is an herb related to onion, leeks, and chives. It is commonly used for conditions related to the heart and blood system.
Garlic produces a chemical called allicin. This is what seems to make garlic work for certain conditions. Allicin also makes garlic smell. Some products are made "odorless" by aging the garlic, but this process can also change the effects of garlic.
People commonly use garlic for high blood pressure, high levels of cholesterol or other fats in the blood, and hardening of the arteries. It is also used for the common cold, osteoarthritis, and many other conditions, but there is no good scientific evidence to support these uses. There is also no good evidence to support using garlic for COVID-19.
- Atherosclerosis. When used alone or in combination with other ingredients, oral garlic seems to slow the progression of atherosclerosis.
Login for details - Diabetes. Most clinical research suggests that oral garlic, taken alone or in combination with metformin for at least 12 weeks, modestly reduces fasting blood glucose levels in patients with diabetes. It is unclear if garlic improves postprandial glucose levels or glycated hemoglobin (HbA1c).
Login for details - Endometriosis. Oral garlic seems to improve pain in people with endometriosis.
Login for details - Hyperlipidemia. Most research shows that taking oral garlic for at least 8 weeks seems to modestly reduce total and low-density lipoprotein (LDL) cholesterol levels in patients with hyperlipidemia. However, evidence is conflicting on whether garlic improves high-density lipoprotein (HDL) cholesterol or triglyceride levels.
Login for details - Hypertension. Some clinical research suggests that oral garlic seems to modestly reduce blood pressure in hypertensive and normotensive patients.
Login for details - Nonalcoholic fatty liver disease (NAFLD). Oral garlic seems to reduce the severity of hepatic steatosis in patients with NAFLD.
Login for details - Periodontitis. Oral aged garlic extract seems to improve some measures of gum health in people with mild to moderate periodontitis.
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- Gastric cancer. Oral garlic does not seem to prevent gastric cancer.
Login for details - Helicobacter pylori. Oral garlic does not seem to be beneficial for Helicobacter pylori eradication.
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- Allergic rhinitis (hay fever). Login for details
- Alopecia areata. Topical garlic may increase hair growth by a small amount.
Login for details - Asthma. Login for details
- Athletic performance. It is unclear if oral garlic is beneficial for athletic performance.
Login for details - Benign prostatic hyperplasia (BPH). It is unclear if oral garlic is beneficial for BPH.
Login for details - Bladder cancer. Login for details
- Breast cancer. It is unclear if oral garlic prevents breast cancer.
Login for details - Bronchitis. Login for details
- Cardiovascular disease (CVD). It is unclear if oral garlic is beneficial for reducing CVD risk factors in adults with hypercholesterolemia.
Login for details - Chronic fatigue syndrome (CFS). Login for details
- Colorectal cancer. It is unclear if oral garlic prevents colorectal cancer.
Login for details - Common cold. Oral garlic might reduce the frequency of the common cold when used prophylactically.
Login for details - Corns. It is unclear if topical garlic is beneficial for corns.
Login for details - Coronary heart disease (CHD). It is unclear if oral garlic is beneficial for CHD.
Login for details - Coronavirus disease 2019 (COVID-19). It is unclear if oral garlic is beneficial for COVID-19.
Login for details - Cystic fibrosis. It is unclear if oral garlic is beneficial for cystic fibrosis.
Login for details - Dental hypersensitivity. Login for details
- Denture stomatitis. It is unclear if topical garlic as a mouthwash is beneficial for denture stomatitis.
Login for details - Diabetic retinopathy. It is unclear if oral garlic is beneficial for diabetic retinopathy.
Login for details - Diarrhea. Login for details
- Dysmenorrhea. Login for details
- Esophageal cancer. It is unclear if oral garlic prevents esophageal cancer.
Login for details - Exercise-induced muscle soreness. It is unclear if oral garlic is beneficial for exercise-induced muscle soreness.
Login for details - Fatigue. Login for details
- Familial hypercholesterolemia. Oral garlic does not seem to improve blood lipid levels in children with familial hypercholesterolemia.
Login for details - Fibrocystic breast disease. Oral garlic has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Gastritis. Oral garlic has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Gout. Login for details
- Hepatitis. It is unclear if oral garlic is beneficial for hepatitis.
Login for details - Hepatopulmonary syndrome. It is unclear if oral garlic is beneficial for hepatopulmonary syndrome.
Login for details - Influenza. Oral garlic has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Lead toxicity. It is unclear if oral garlic is beneficial for lead toxicity.
Login for details - Lung cancer. It is unclear if oral garlic prevents lung cancer.
Login for details - Metabolic syndrome. Small studies suggest that oral garlic may improve some metabolic parameters in patients with metabolic syndrome.
Login for details - Mosquito repellent. It is unclear if oral garlic is beneficial as a mosquito repellent.
Login for details - Multiple myeloma. It is unclear if oral garlic prevents multiple myeloma.
Login for details - Muscle strength. It is unclear if oral garlic is beneficial for muscle strength.
Login for details - Obesity. It is unclear if oral garlic is beneficial for obesity.
Login for details - Onychomycosis. Login for details
- Oropharyngeal candidiasis. It is unclear if oral garlic is beneficial for oropharyngeal candidiasis.
Login for details - Osteoarthritis. It is unclear if oral garlic is beneficial for osteoarthritis.
Login for details - Otitis media. Login for details
- Peripheral arterial disease (PAD). Oral garlic seems to improve pain-free walking distance by a small amount in patients with PAD. However, it does not seem to improve blood pressure.
Login for details - Polycystic ovary syndrome (PCOS). It is unclear if oral garlic is beneficial for PCOS.
Login for details - Pre-eclampsia. It is unclear if oral garlic prevents pre-eclampsia during the third trimester.
Login for details - Premenstrual syndrome (PMS). It is unclear if oral garlic is beneficial for PMS.
Login for details - Prostate cancer. Observational research on the relationship between garlic intake and prostate cancer risk is conflicting. It is unclear if garlic supplements are beneficial in patients with prostate cancer.
Login for details - Rheumatoid arthritis (RA). Oral garlic seems to reduce pain by a small amount in patients with RA.
Login for details - Scleroderma. It is unclear if oral garlic is beneficial for scleroderma.
Login for details - Stress. Login for details
- Tick repellent. It is unclear if oral garlic is beneficial as a tick repellent.
Login for details - Tinea capitis. Login for details
- Tinea corporis. It is unclear if topical garlic is beneficial for tinea corporis.
Login for details - Tinea cruris. It is unclear if topical garlic is beneficial for tinea cruris.
Login for details - Tinea pedis. It is unclear if topical garlic is beneficial for tinea pedis.
Login for details - Trichomoniasis. Login for details
- Tuberculosis. Login for details
- Unstable angina. It is unclear if intravenous garlic is beneficial for unstable angina.
Login for details - Urinary tract infections (UTIs). Login for details
- Vaginal candidiasis. It is unclear if oral or topical garlic is beneficial for vaginal candidiasis.
Login for details - Warts. It is unclear if topical garlic is beneficial for warts.
Login for details - Wound healing. It is unclear if topical garlic is beneficial for wound healing.
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When taken by mouth: Garlic is likely safe for most people. Garlic has been used safely for up to 7 years. It can cause side effects such as bad breath, heartburn, gas, and diarrhea. These side effects are often worse with raw garlic. Garlic might also increase the risk of bleeding and cause allergic reactions in some people.
When applied to the skin: Garlic products are possibly safe. Gels, pastes, and mouthwashes containing garlic have been used for up to 3 months. But garlic might cause skin damage that is similar to a burn. RAW garlic is possibly unsafe when applied to the skin. It might cause severe skin irritation.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Garlic is likely safe to take by mouth in the amounts normally found in food. Garlic is possibly unsafe when used in medicinal amounts during pregnancy and when breast-feeding. There isn't enough reliable information about the safety of applying garlic to the skin if you are pregnant or breast feeding. Stay on the safe side and avoid use.Children: Garlic is possibly safe when taken by children in doses of up to 300 mg three times daily for up to 8 weeks. There isn't enough reliable information to know if garlic is safe when used in larger doses or for longer than 8 weeks. It is possibly unsafe to apply raw garlic to the skin. It might burn the skin.
Bleeding disorder: Garlic, especially fresh garlic, might increase the risk of bleeding.
Surgery: Garlic might prolong bleeding and interfere with blood pressure. Garlic might also lower blood sugar levels. Stop taking garlic at least two weeks before a scheduled surgery.
Atazanavir (Reyataz)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might reduce how much atazanavir the body absorbs. This might decrease how well atazanavir works.
Isoniazid
Interaction Rating=Moderate Be cautious with this combination.
Garlic might reduce how much isoniazid the body absorbs. This might decrease how well isoniazid works.
Medications changed by the liver (Cytochrome P450 2E1 (CYP2E1) substrates)
Interaction Rating=Moderate Be cautious with this combination.
Some medications are changed and broken down by the liver. Garlic might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.
Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)
Interaction Rating=Moderate Be cautious with this combination.
Some medications are changed and broken down by the liver. Garlic might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.
Medications for HIV/AIDS (Protease inhibitors)
Interaction Rating=Moderate Be cautious with this combination.
Taking garlic might decrease the amount of HIV/AIDS medication the body can absorb. This could decrease the effects of some medications used for HIV/AIDS.
Medications for diabetes (Antidiabetes drugs)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might lower blood sugar levels. Taking garlic along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.
Medications for high blood pressure (Antihypertensive drugs)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might lower blood pressure. Taking garlic along with medications that lower blood pressure might cause blood pressure to go too low. Monitor your blood pressure closely.
Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might slow blood clotting. Taking garlic along with medications that also slow blood clotting might increase the risk of bruising and bleeding.
Saquinavir (Fortovase, Invirase)
Interaction Rating=Moderate Be cautious with this combination.
Saquinavir is a medication taken for HIV. Garlic might decrease how much saquinavir goes into the blood. This might decrease the effects of saquinavir.
Sofosbuvir (Sovaldi)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might increase how quickly the body gets rid of sofosbuvir. This might decrease the effects of sofosbuvir.
Tacrolimus (Prograf)
Interaction Rating=Moderate Be cautious with this combination.
Garlic might decrease how quickly the liver breaks down tacrolimus. Taking garlic with tacrolimus might increase the effects and side effects of tacrolimus.
Warfarin (Coumadin)
Interaction Rating=Moderate Be cautious with this combination.
Warfarin is used to slow blood clotting. Garlic might increase the effects of warfarin. Taking garlic along with warfarin might increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.
Herbs and supplements that might lower blood pressure: Garlic might lower blood pressure. Taking it with other supplements that have the same effect might cause blood pressure to drop too much. Examples of supplements with this effect include andrographis, casein peptides, L-arginine, niacin, and stinging nettle.
Herbs and supplements that might lower blood sugar: Garlic might lower blood sugar. Taking it with other supplements with similar effects might lower blood sugar too much. Examples of supplements with this effect include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus.
Herbs and supplements that might slow blood clotting: Garlic might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include ginger, ginkgo, nattokinase, and Panax ginseng.
There are no known interactions with foods.
Garlic has most often been used by adults in doses of 2400 mg by mouth daily for 12 months. Garlic extracts are usually standardized by the amount of allicin they contain. This typically ranges from 1.1% to 1.3%. It's a good idea to look for supplements that are coated (enteric coating) so they will dissolve in the intestine and not in the stomach. Garlic is also used in creams, gels, pastes, and mouthwashes. Speak with a healthcare provider to find out what dose might be best for a specific condition.
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