What supplements not to mix with ashwagandha?

October 10, 2025 •

3 min read

Used for centuries in Ayurvedic medicine to help the body manage stress and anxiety, ashwagandha's popularity as an adaptogen has grown significantly. Given its potent effects, it is crucial to understand what supplements not to mix with ashwagandha to prevent harmful interactions and ensure your safety.

Quick Summary

Ashwagandha can interact dangerously with various supplements and medications by amplifying effects or interfering with treatment. Combinations with sedatives, kava, valerian root, immunosuppressants, and thyroid medications should be avoided or monitored closely by a healthcare provider.

Key Points

Sedative Supplements: Do not mix ashwagandha with other sedative supplements like kava or valerian root, as the combination can cause excessive drowsiness, slowed breathing, and impaired cognitive function.
Autoimmune Conditions: Avoid ashwagandha if you have an autoimmune disease (e.g., MS, lupus, RA), as it can stimulate the immune system and potentially worsen symptoms.
Thyroid Medication: Do not combine ashwagandha with thyroid medication, as it may increase thyroid hormone levels, leading to dangerously high levels (thyrotoxicosis).
Liver Health: Combining ashwagandha with other supplements known to affect the liver, such as kava, can increase the risk of liver damage.
Serotonin-Affecting Supplements: Be cautious when combining ashwagandha with supplements like St. John's Wort, as there is a theoretical risk of serotonin syndrome.
Pre-Surgery: Discontinue ashwagandha at least two weeks before any scheduled surgery, as it can slow the central nervous system and interfere with anesthesia.

As an adaptogenic herb, ashwagandha has a range of potential physiological effects, including calming the nervous system, modulating the immune system, and influencing hormone levels. These very actions, however, can lead to serious adverse effects when combined with certain medications or other supplements that have similar properties. To use ashwagandha safely, it is essential to consult with a healthcare provider and understand the key interactions.

Interactions with Sedative and Calming Supplements

Ashwagandha has inherent sedative properties, and its scientific name, Withania somnifera, even means "sleep-inducing" in Latin. Combining it with other supplements that also promote sleep or calmness can lead to excessive drowsiness, impaired cognitive function, and even respiratory issues.

Kava (Piper methysticum) and Valerian Root (Valeriana officinalis)

Both kava and valerian root are known for their relaxing and sedative effects. When taken with ashwagandha, the combined sedative action can be dangerously amplified. There have also been rare cases of liver injury linked to ashwagandha supplements, and kava is also known to pose a risk to liver health. The combination of the two could increase this risk substantially.

St. John's Wort (Hypericum perforatum)

While not primarily a sedative, St. John's wort is used for anxiety and depression and affects neurotransmitter levels. Some evidence suggests ashwagandha may increase serotonin levels, and combining it with another supplement that also impacts serotonin could theoretically increase the risk of serotonin syndrome, a potentially life-threatening condition.

Supplements Interacting with Medical Conditions

Ashwagandha's adaptogenic and immune-modulating effects can profoundly impact various health conditions and their treatments. Individuals with pre-existing conditions need to be particularly cautious.

For Autoimmune Disorders

Ashwagandha can potentially stimulate the immune system by increasing its activity. For individuals with autoimmune diseases like multiple sclerosis (MS), lupus (SLE), or rheumatoid arthritis (RA), this could exacerbate symptoms or trigger a flare-up. If you have an autoimmune condition, avoid ashwagandha unless explicitly approved by your doctor.

For Thyroid Conditions

Ashwagandha has been shown to increase thyroid hormone levels, which can be beneficial for those with underactive thyroid (hypothyroidism). However, this effect is problematic for anyone with an overactive thyroid (hyperthyroidism) or those on thyroid hormone replacement medication like levothyroxine. Combining them could lead to thyrotoxicosis, or excessive thyroid hormone, causing symptoms like a fast heartbeat, nervousness, and weight loss.

The Problem with Unknown Ingredients

Herbal supplement industry regulation is often less stringent than that of pharmaceuticals. As a result, contamination or mislabeling can occur, making it difficult to know exactly what you are consuming. In some reported cases of liver injury involving ashwagandha, it was unclear if the herb itself or another contaminant caused the reaction. This reinforces the importance of purchasing products from reputable manufacturers who adhere to good manufacturing practices (GMP).

Comparison of Ashwagandha with Potentially Interacting Herbs


Feature	Ashwagandha	Kava	Valerian Root	St. John's Wort
Primary Effect	Calming, adaptogenic	Calming, relaxing	Sedative	Mood enhancement
Main Interaction	Sedative effects, immune system	Liver toxicity, sedative effects	Sedative effects	Serotonin levels
Effect on Body	Lowers cortisol, influences hormones	Affects CNS, can be hepatotoxic	Slows down CNS	Inhibits serotonin reuptake
Key Concern	Amplified sedation with other herbs	Liver damage when combined	Exaggerated drowsiness	Serotonin syndrome risk

Conclusion: Prioritize Safety and Professional Advice

Before adding ashwagandha to your regimen, it's critical to consider its potential interactions with other supplements and any underlying medical conditions you may have. The herb can interact dangerously with sedatives, thyroid medication, and immunosuppressants, and it's best to avoid other sedative or mood-altering supplements like kava, valerian root, and St. John's wort. Given the complexities and potential risks, always consult a qualified healthcare professional before taking ashwagandha, especially if you are on medication or have an autoimmune or thyroid disorder. A doctor can help determine if it's safe for you and monitor any potential side effects.

For more information on the interactions of herbal supplements, the National Center for Complementary and Integrative Health is an excellent resource.

Frequently Asked Questions

No, it is highly discouraged to combine ashwagandha with other sedative herbs like kava and valerian root. Ashwagandha has natural sedative effects, and combining them can lead to excessive drowsiness, fatigue, and other dangerous side effects.

While not well-studied, there is a theoretical risk that combining ashwagandha with St. John's Wort could increase serotonin levels in the body too much, potentially leading to a serious condition called serotonin syndrome.

If you have an autoimmune disease such as lupus, MS, or rheumatoid arthritis, you should avoid ashwagandha. The herb can increase immune system activity, which could trigger a flare-up or worsen your symptoms.

No, you should not take ashwagandha with thyroid medication. Ashwagandha can increase thyroid hormone levels, interfering with the medication's effectiveness and potentially leading to excessively high thyroid hormone levels.

Ashwagandha may slow down the central nervous system, and for this reason, healthcare providers recommend stopping its use at least two weeks before a scheduled surgery to avoid interference with anesthesia.

Yes. If you have a pre-existing liver condition, you should avoid taking ashwagandha. There have been rare reports of liver injury linked to ashwagandha, and combining it with other substances that may stress the liver, like kava, increases the risk.

No, pregnant and breastfeeding women should avoid taking ashwagandha. The effects on these populations have not been reliably studied, and it is considered likely unsafe during pregnancy.