Potential Side Effects of Holy Basil Tea

December 27, 2025 •

3 min read

In Ayurveda, holy basil (Tulsi) is revered as a potent medicinal herb, but like all remedies, it is not without potential risks. Understanding what are the side effects of holy basil tea is crucial for safe consumption, especially for individuals with underlying health conditions or those on medication.

Quick Summary

Holy basil tea can cause low blood sugar, increase bleeding risk, affect fertility, and potentially worsen hypothyroidism. Pregnant or breastfeeding women, and those on specific medications should be cautious or avoid it. High doses might also lead to digestive issues like nausea or diarrhea.

Key Points

Blood Sugar: Holy basil tea can lower blood sugar, posing a risk of hypoglycemia for people with diabetes or those on blood-sugar-lowering medication.
Bleeding Risk: It can slow blood clotting, increasing the risk of bruising and bleeding, especially when combined with blood-thinning medications.
Fertility: Animal studies suggest holy basil may impact fertility by reducing sperm count and affecting reproductive organ health.
Pregnancy: The herb may cause uterine contractions and is considered potentially unsafe for pregnant or breastfeeding women.
Medication Interactions: Holy basil can interact with a range of medications, including blood thinners, anti-diabetic drugs, sedatives, and thyroid hormone replacements.
Liver Damage: Excessive consumption of the eugenol found in tulsi leaves has been linked to potential liver damage in high doses.
Digestive Issues: Some individuals may experience mild side effects like nausea or diarrhea, particularly with large quantities.

Common Digestive Discomforts

While many people tolerate holy basil tea well, some may experience mild gastrointestinal issues, especially when starting consumption or taking it in high doses.

Nausea and Diarrhea

Nausea and diarrhea are among the most commonly reported minor side effects of holy basil, particularly with concentrated extracts or excessive intake. Starting with a lower dose and observing your body's reaction can help mitigate these symptoms.

Impact on Blood Sugar Levels

One of holy basil's most cited properties is its ability to help lower blood sugar levels. While beneficial for many, this effect can pose a risk for others.

Risk of Hypoglycemia

For individuals with diabetes, or those already taking anti-diabetic medications, combining these treatments with holy basil tea could cause blood sugar to drop too low, a condition known as hypoglycemia. Symptoms of hypoglycemia include dizziness, fatigue, and confusion. Close monitoring of blood sugar levels is advised for diabetic patients consuming tulsi tea.

Potential for Increased Bleeding Risk

Holy basil has natural properties that can affect blood clotting.

Interactions with Blood-Thinning Medications

Individuals taking anticoagulant or antiplatelet drugs, such as warfarin, heparin, or aspirin, should be aware that holy basil can slow blood clotting. This can increase the risk of bruising and bleeding. It is crucial to consult a healthcare provider before using holy basil tea if you are on any blood-thinning medication. Additionally, it is recommended to stop consuming holy basil at least two weeks before any scheduled surgery to prevent excessive bleeding.

Concerns Regarding Fertility and Pregnancy

Specific populations, including those who are pregnant, breastfeeding, or trying to conceive, should exercise extreme caution with holy basil.

Effects on Reproductive Health

Animal studies have shown that high doses of holy basil can impact reproductive health, potentially decreasing fertility in both males and females. Furthermore, holy basil has been shown to cause uterine contractions in animal studies, which could potentially increase the risk of miscarriage. Due to insufficient human studies, pregnant and breastfeeding women are advised to avoid holy basil to be on the safe side.

Interactions with Other Medications and Health Conditions

Beyond blood thinners and diabetes medications, holy basil can interact with other drugs and exacerbate certain health conditions.

Thyroid Function and Hypothyroidism

Some evidence suggests that holy basil might decrease levels of the thyroid hormone thyroxine. For people with hypothyroidism, or low thyroid function, this could theoretically worsen their condition. Anyone with a thyroid condition should discuss holy basil use with their doctor before incorporating it into their routine.

Additive Effects with Blood Pressure Medications

As holy basil can have a blood pressure-lowering effect, combining it with antihypertensive drugs could cause blood pressure to drop too low, leading to lightheadedness or fainting.

Interactions with Sedatives

Animal data also suggests that holy basil may enhance the sedating effects of barbiturates, so it is best to avoid this combination.

Comparing Holy Basil Tea vs. Other Herbal Teas

To put the side effects of holy basil into perspective, here is a comparison with other popular herbal teas.


Feature	Holy Basil (Tulsi) Tea	Chamomile Tea	Peppermint Tea
Potential Side Effects	Mild nausea/diarrhea, hypoglycemia risk, bleeding risk, affects fertility/pregnancy	Allergic reactions (especially for those with ragweed allergies), potential blood thinner interaction	Acid reflux, allergic reactions, potential digestive upset
Primary Use	Adaptogen (stress relief), immune support	Relaxation, sleep aid, digestive issues	Digestive aid, headache relief
Precautions	Pregnancy, low blood sugar, blood thinners, surgery	Pregnancy, individuals with ragweed allergy, blood thinners	Pregnancy, severe acid reflux

Conclusion: Responsible Consumption is Key

While holy basil tea is celebrated for its many health benefits, responsible consumption is essential. The potential side effects, particularly concerning blood sugar, bleeding disorders, fertility, and pregnancy, highlight the importance of individual health considerations. Always consult with a healthcare professional before adding holy basil tea or any new herbal supplement to your regimen, especially if you have pre-existing health conditions or are taking medication. Starting with moderate doses and listening to your body can help you enjoy the benefits while minimizing risks.

For more information on general dietary supplement safety, you can visit the National Institutes of Health website [https://ods.od.nih.gov/HealthInformation/DS_WhatToKnow.aspx].

Frequently Asked Questions

Individuals who are pregnant, breastfeeding, or trying to conceive should avoid holy basil tea. People with diabetes, those on blood-thinning medication, and individuals with hypothyroidism should also consult a doctor before use.

Some animal studies suggest that high doses of holy basil may reduce fertility in both males and females. Due to this potential risk, it is advised to avoid consumption if you are trying to conceive.

Holy basil is considered possibly unsafe during pregnancy. Animal studies have shown that high doses can reduce the chances of a successful pregnancy, and the herb may stimulate uterine contractions.

Yes, holy basil can interact with several medications, including blood thinners (like warfarin), diabetes medications, and thyroid hormone medications.

Yes, holy basil tea can lower blood sugar levels. This is a beneficial effect for some but can be dangerous for diabetic individuals or those at risk of hypoglycemia.

The most common digestive side effects are mild nausea or diarrhea, which typically occur with excessive intake or if you are sensitive to the herb.

Yes, because holy basil can slow blood clotting, it is recommended to stop taking it at least two weeks before any scheduled surgery to minimize the risk of bleeding.