What Should Not Be Taken with Oregano? A Guide to Safe Supplement Use

October 8, 2025 •

4 min read

While culinary use of oregano is generally safe, research indicates that taking medicinal amounts, particularly concentrated oil of oregano, can have significant interactions with various drugs and supplements. This necessitates understanding what should not be taken with oregano to prevent adverse health effects.

Quick Summary

Concentrated oregano products, like oil of oregano, should not be taken with blood thinners, diabetes medication, or lithium. They can also interfere with the absorption of certain minerals and are unsafe for pregnant or breastfeeding women. Always consult a doctor before use.

Key Points

Blood Thinners and Oregano: Combining concentrated oregano with anticoagulants like warfarin or antiplatelet drugs like aspirin significantly increases the risk of bleeding and bruising.
Diabetes Medication Risk: Oregano can lower blood sugar levels, which when taken with diabetes medication, can lead to dangerous hypoglycemia.
Lithium and Oregano: Oregano's diuretic effect can interfere with the body's clearance of lithium, potentially causing a dangerous buildup of the drug.
Surgery Precautions: Stop taking oregano supplements at least two weeks before any scheduled surgery due to an increased risk of bleeding.
Pregnancy and Breastfeeding Warning: High, medicinal doses of oregano are considered unsafe during pregnancy and should be avoided due to the potential risk of miscarriage.
Mineral Absorption Interference: The tannins in oregano can reduce the absorption of minerals like iron, copper, and zinc; take supplements separately.
Allergy Risk: Individuals allergic to other mint-family herbs (e.g., basil, mint, sage) are at a higher risk of an allergic reaction to oregano.

While the herb oregano is a staple in many cuisines, its concentrated forms—such as oil of oregano or supplements—possess powerful compounds that can interact with medications and other supplements. The potential for adverse effects rises significantly when consuming amounts larger than what is typically used for flavoring food. It is crucial to be aware of these risks and consult a healthcare provider before incorporating medicinal oregano into your regimen.

Medications to Avoid with Oregano

Blood-Thinning Medications

One of the most critical interactions is with anticoagulant and antiplatelet drugs. The compounds in oregano can inhibit blood clotting, creating an additive effect when combined with blood thinners. This can significantly increase the risk of bruising, spontaneous bleeding, or more severe hemorrhagic events.

This includes a wide range of common medications:

Anticoagulants: Warfarin (Coumadin), dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis).
Antiplatelets: Aspirin, clopidogrel (Plavix), and prasugrel (Effient).
Low Molecular Weight Heparins: Dalteparin (Fragmin), and enoxaparin (Lovenox).

Diabetes Medications

Oregano may have blood sugar-lowering effects. For individuals with diabetes, this poses a risk of hypoglycemia, or dangerously low blood sugar, especially when taken with antidiabetic medications. If you are managing your blood sugar with medication, a supplement containing oregano could cause levels to drop too low.

Common diabetes medications that interact with oregano include:

Glimepiride (Amaryl)
Glyburide (Micronase)
Metformin (Glucophage)
Insulin

Lithium

Oregano can act as a natural diuretic, increasing urination. This can interfere with the body's ability to excrete lithium effectively, leading to higher-than-desired levels of lithium in the blood and potentially causing adverse effects. If you are on lithium therapy, it is important to avoid oregano supplements unless otherwise advised by your doctor.

Diuretic Medications

Because of its own diuretic properties, concentrated oregano can intensify the effects of prescription diuretics. This could lead to increased fluid and electrolyte loss, potentially causing dehydration or other side effects.

Supplements to Avoid with Oregano

Herbs That Slow Blood Clotting

Taking oregano alongside other natural health products known to slow blood clotting further elevates the risk of bruising and bleeding. Examples include:

Garlic
Ginger
Ginkgo
Certain types of ginseng
Red clover

Mineral Supplements

The tannins present in oregano can bind with certain minerals, reducing their absorption in the body. If you are taking supplements for minerals such as iron, copper, or zinc, it is best to take them at least two hours apart from oregano supplements.

Other Blood Sugar-Lowering Herbs

Just as with prescription diabetes medications, combining oregano with other herbs that lower blood sugar can create a compounding effect. These include:

Bitter melon
Chromium
Aloe

Special Considerations and Precautions

Before Surgery

Due to its ability to affect blood clotting, consuming large doses of oregano poses a bleeding risk during and after surgical procedures. Medical professionals universally recommend stopping all oregano supplements at least two weeks before any scheduled surgery.

Pregnancy and Breastfeeding

Medicinal amounts of oregano are considered possibly unsafe during pregnancy, as there is concern that high doses may increase the risk of miscarriage. There is also insufficient data to determine its safety during breastfeeding, so it is best to err on the side of caution and avoid it.

Allergic Reactions

Oregano belongs to the mint family (Lamiaceae). Individuals with known allergies to other mint-family plants, such as basil, lavender, hyssop, marjoram, mint, or sage, may experience an allergic reaction to oregano.

Comparison of Oregano Interactions


Interacting Agent	Mechanism of Interaction	Potential Risk	Recommendation
Blood Thinners (e.g., Warfarin, Aspirin)	Oregano slows blood clotting, enhancing the drug's effect.	Increased risk of bleeding and bruising.	Avoid high doses of oregano. Discontinue two weeks before surgery.
Diabetes Medications (e.g., Metformin, Insulin)	Oregano can lower blood sugar levels.	Risk of hypoglycemia (low blood sugar).	Monitor blood sugar closely. Consult a doctor before combining.
Lithium	Oregano's diuretic effect can alter how the body excretes lithium.	Higher lithium levels and potential toxicity.	Avoid oregano supplements. Consult a doctor about potential dosage adjustments.
Mineral Supplements (Iron, Copper, Zinc)	Tannins in oregano can reduce mineral absorption.	Decreased effectiveness of mineral supplements.	Take supplements at least two hours apart from oregano.

Conclusion

While adding a sprinkle of oregano to your pizza or pasta is harmless for most people, using concentrated supplements like oil of oregano requires careful consideration. The potential for dangerous interactions with common medications and supplements is well-documented and should not be ignored. Individuals on blood thinners, diabetes medication, or lithium, as well as those who are pregnant, should be especially cautious and avoid medicinal doses of oregano. Always inform your healthcare provider about any herbal supplements you are taking to ensure your safety and the effectiveness of your medical treatment. For additional information on herbal supplement safety, resources like MedlinePlus offer valuable guidance.

Frequently Asked Questions

Yes, typical culinary use of oregano in food is generally considered safe for most people. The interaction risk arises with concentrated, medicinal amounts found in supplements like oil of oregano.

You should stop taking oil of oregano and any other oregano supplements at least two weeks before any scheduled surgery. This minimizes the risk of excessive bleeding during and after the procedure.

Taking oregano with diabetes medication, such as metformin or insulin, can cause your blood sugar to drop too low, resulting in a dangerous condition called hypoglycemia. Monitor your blood sugar closely and consult your doctor.

No, taking medicinal amounts of oregano is considered possibly unsafe during pregnancy due to concerns that it might cause miscarriage. It is best to avoid it.

Yes, the tannins in oregano can interfere with the absorption of iron. To avoid this interaction, take your iron supplement at least two hours before or after consuming oregano.

Individuals taking blood thinners, diabetes medication, or lithium should be especially cautious. Additionally, pregnant or breastfeeding women and those with a known allergy to the mint family should avoid concentrated oregano.

If you experience any adverse effects like stomach upset, allergic reactions, or unusual bleeding, stop taking the oregano immediately and consult a healthcare professional.