Who Should Not Eat Garlic? A Guide to Dietary Restrictions and Caution

November 4, 2025 •

4 min read

Garlic has been used medicinally for thousands of years, and its potent compounds offer numerous health benefits, from heart health support to antimicrobial properties. However, despite its wide popularity and perceived safety, there are specific health conditions and circumstances under which some individuals should not eat garlic or should significantly limit their consumption.

Quick Summary

Certain individuals with bleeding disorders, GERD, IBS, or garlic allergies should avoid or limit consumption. High doses can worsen digestive issues and interfere with some medications.

Key Points

Blood Thinners and Bleeding: Individuals on anticoagulant medications like warfarin or with bleeding disorders should be cautious, as garlic has blood-thinning properties and can increase bleeding risk.
Pre-Surgery Precautions: Stop taking garlic, especially supplements, at least two weeks before surgery due to its ability to prolong bleeding time.
GERD and Digestive Issues: Those with gastroesophageal reflux disease (GERD), IBS, or stomach ulcers may find that garlic exacerbates symptoms like heartburn, bloating, and gas.
Garlic Allergies: Though uncommon, some individuals may have an allergy to garlic, which can cause skin rashes, hives, nausea, and in severe cases, anaphylaxis.
Pregnancy and Breastfeeding: While culinary amounts are likely safe, large or supplemental doses during pregnancy or breastfeeding are possibly unsafe and should be discussed with a doctor.
Hypotension Risk: People with naturally low blood pressure should be careful, as garlic can lower blood pressure further, potentially causing dizziness.

Garlic is a staple in many cuisines and a popular natural remedy, celebrated for its pungent flavor and health-promoting compounds, most notably allicin. Yet, its powerful properties are not without potential risks for some people. Understanding these risks is crucial for making informed dietary choices. Here is a comprehensive look at who should not eat garlic and why.

Individuals with Bleeding Disorders or on Anticoagulant Medication

One of the most critical warnings regarding garlic consumption concerns its effect on blood clotting. Garlic possesses antithrombotic (blood-thinning) properties, which can be beneficial for some but dangerous for others.

Increased Bleeding Risk

Bleeding Disorders: For individuals with conditions like hemophilia, consuming large amounts of garlic can increase the risk of bleeding.
Anticoagulant Medications: Patients taking blood thinners such as warfarin (Coumadin), aspirin, or clopidogrel should use caution. Garlic supplements, in particular, have a more concentrated effect and can enhance the medication's blood-thinning properties, potentially leading to excessive bruising or bleeding.
Pre-Surgery: Medical professionals advise discontinuing garlic supplements and large quantities of garlic at least two weeks before any scheduled surgery, as it can prolong bleeding time and interfere with blood pressure.

People with Gastrointestinal Issues

For many, garlic is a digestive irritant that can trigger or worsen symptoms of pre-existing conditions.

Aggravated Digestive Conditions

Gastroesophageal Reflux Disease (GERD): Garlic can relax the lower esophageal sphincter, the muscle preventing stomach acid from flowing back into the esophagus. This can trigger heartburn and other uncomfortable GERD symptoms. Raw garlic is especially potent in causing this effect.
Irritable Bowel Syndrome (IBS): Garlic is high in fructans, a type of fermentable carbohydrate (FODMAP) that can be poorly absorbed in the small intestine. This can lead to fermentation by gut bacteria, causing uncomfortable symptoms like bloating, gas, stomach pain, and diarrhea in sensitive individuals.
Stomach Ulcers and Gastritis: Compounds in garlic can irritate the mucous membranes of the stomach and intestines. Those with ulcers or gastritis should be cautious, as it could exacerbate pain and inflammation.

Pregnant and Breastfeeding Individuals

While garlic in food quantities is generally considered safe, large amounts or supplements should be approached with caution during pregnancy and breastfeeding.

Maternal and Infant Health Concerns

Pregnancy: Excessive garlic intake during pregnancy has been anecdotally associated with potential risks, including stomach irritation and, in high supplemental doses, a possible increased risk of bleeding during delivery. Always consult a doctor before taking garlic supplements.
Breastfeeding: Some evidence suggests that a mother's consumption of large quantities of garlic can affect the taste of breast milk, which may be unappealing to the baby. It is recommended to stick to normal food-flavoring quantities.

People with Garlic Allergies

Though uncommon, allergic reactions to garlic do occur and can range from mild to severe.

Allergic Reactions

Symptoms: A garlic allergy can manifest as skin rashes, itching, hives, nausea, or swelling. Respiratory symptoms like rhinitis (nasal inflammation) or asthma may also occur, especially from inhaling garlic dust.
Cross-Reactivity: Individuals with an allergy to other Allium species, such as onions or leeks, may also be sensitive to garlic.
Anaphylaxis: In rare, severe cases, a garlic allergy can lead to anaphylaxis, a life-threatening reaction.

Excessive Consumption Side Effects

Even for those without underlying conditions, overdoing it with garlic can lead to unpleasant side effects.

Digestive Discomfort: Consuming too much garlic can cause gas, bloating, and diarrhea.
Low Blood Pressure: Garlic is known to lower blood pressure. For individuals already with low blood pressure (hypotension) or on blood pressure-lowering medication, too much garlic could cause a dangerous drop, leading to dizziness or weakness.

Comparison Table: Raw Garlic vs. Cooked Garlic Effects


Aspect	Raw Garlic	Cooked Garlic
Potency	Higher concentration of allicin, the active compound.	Lower allicin content, as heat reduces its potency.
Digestive Irritation	More likely to cause heartburn and irritate the digestive tract.	Generally less irritating to the stomach and digestive system.
Blood-Thinning	Stronger antiplatelet effect, increasing bleeding risk more significantly.	Milder effect on blood clotting, posing less risk in moderate amounts.
Taste & Aroma	Stronger, more pungent flavor and persistent body odor.	Milder, nuttier flavor and less lingering odor.

Conclusion

While garlic is a celebrated and healthful food for most, it is not universally safe. Individuals with bleeding disorders, GERD, IBS, or a known garlic allergy should exercise caution or avoid it entirely. For those on blood thinners or anticipating surgery, limiting or halting garlic intake is a critical medical precaution. Pregnant and breastfeeding women should also be mindful of their consumption, sticking to moderate food quantities. When in doubt, it is always best to consult a healthcare provider to ensure that adding garlic to your diet is safe for your specific health needs.

For more information on the safety and effectiveness of dietary supplements like garlic, refer to the National Center for Complementary and Integrative Health.

Frequently Asked Questions

If you are on blood-thinning medication like warfarin, you should be cautious with your garlic intake and consult your doctor. Large amounts, especially from supplements, can increase your risk of bleeding.

Yes, for many people, especially those with GERD, garlic can relax the lower esophageal sphincter, which allows stomach acid to back up into the esophagus, causing or worsening heartburn and acid reflux symptoms.

Garlic contains fructans, a type of carbohydrate that is difficult for some people to digest. These fructans ferment in the gut, causing gas, bloating, and other digestive discomfort, particularly in individuals with Irritable Bowel Syndrome (IBS).

Yes, it is highly recommended to stop consuming garlic, particularly in supplement form, at least two weeks before any scheduled surgery. This is because garlic can slow blood clotting and increase the risk of bleeding.

Garlic allergies are not very common but are possible. Symptoms can include skin irritation, rashes, or nausea. Individuals with allergies to other allium vegetables like onions may be at higher risk.

Garlic used in normal cooking quantities is generally safe during pregnancy. However, large or medicinal amounts, often found in supplements, are considered possibly unsafe and should be avoided or discussed with a healthcare provider.

Beyond dietary restrictions, excessive garlic consumption can cause side effects like bad breath and body odor, upset stomach, gas, bloating, and in some cases, dizziness due to a drop in blood pressure.