Ashwagandha Side Effects and Contraindications: Scientific Guide 2026

⏱ 12 min read

By Kóre Labs Team | Published: March 19, 2026

Introduction: The Science Behind Safety

Ashwagandha (Withania somnifera) has established itself as one of the most potent and studied adaptogens for stress management and overall well-being. However, at Kóre Labs, under our "Science First" principle, we recognize that potency comes with responsibility. It's not enough to know the benefits; understanding the possible Ashwagandha side effects and contraindications is crucial for safe and effective supplementation. This article breaks down current clinical evidence to help you make informed decisions about your health, aligned with our commitment to "Quality or Nothing." Your rebirth begins with knowledge.

Common Ashwagandha Side Effects

Although most people tolerate Ashwagandha well, especially at recommended doses, mild side effects can occur. These are usually transient and disappear when adjusting the dose or discontinuing use.

The most frequently reported side effects in clinical studies include:

• Gastrointestinal Discomfort: Nausea, diarrhea, or mild stomach pain are the most common. This is often due to the withanolides, active compounds that can irritate the stomach lining in sensitive individuals or when taken on an empty stomach.
• Drowsiness: Due to its calming properties, some people may experience excessive sedation, especially if taken during the day or in combination with other relaxing substances.
• Headache: Reported on rare occasions, although its direct link to Ashwagandha is not always clear in studies.

It is important to note that the incidence of these side effects is low compared to placebo groups in randomized controlled trials, which underscores the general safety of the plant when used correctly (1).

Absolute Contraindications: When to Avoid It

There are specific situations where the use of Ashwagandha is contraindicated due to potential health risks. At Kóre Labs, we prioritize your safety above all else.

• Pregnancy and Lactation: Ashwagandha has properties that could induce miscarriages, according to animal studies. There is insufficient safety evidence in humans during pregnancy or lactation, so its use is strongly discouraged.
• Autoimmune Diseases: Conditions such as systemic lupus erythematosus (SLE), rheumatoid arthritis, multiple sclerosis, and Hashimoto's thyroiditis can be affected. Ashwagandha can enhance immune system activity, which could exacerbate the symptoms of these diseases. If you suffer from any of these conditions, medical supervision is essential (2).
• Imminent Surgery: Due to its possible effects on blood sugar and the central nervous system, it is recommended to stop Ashwagandha at least two weeks before any scheduled surgery to avoid interactions with anesthesia and postoperative medications.

For more details on the safety of this adaptogen, we invite you to read our guide on what phytotherapy is and contraindications of adaptogens.

Critical Drug Interactions

Ashwagandha can interact with various types of medications, altering their effectiveness or enhancing their side effects. This is crucial if you are undergoing medical treatment.

• Thyroid Medications: Ashwagandha can increase thyroid hormone levels (T3 and T4). If you take levothyroxine or other medications for hypothyroidism, the combination could lead to a hyperthyroid state. Conversely, people with hyperthyroidism should avoid it (3).
• Antidiabetic Medications: Studies suggest that Ashwagandha can lower blood sugar levels. If you take insulin or oral medications for diabetes, there is a risk of hypoglycemia (excessively low blood sugar). Close monitoring of glucose is required.
• Immunosuppressants: As mentioned, by boosting the immune system, Ashwagandha can counteract the effects of medications designed to suppress it (such as those used after transplants or for autoimmune diseases).
• Sedatives and CNS Depressants: Medications such as benzodiazepines, barbiturates, and other sedatives may have their effects enhanced by Ashwagandha, increasing the risk of excessive drowsiness and sedation (4).

Always consult your doctor before combining our Kóre Ashwagandha with any prescription medication. Transparency with your healthcare professional is vital.

Special Populations and Precautions

In addition to absolute contraindications, certain populations should exercise caution when considering Ashwagandha supplementation.

• Hormonal Disorders: Due to its potential impact on thyroid hormones and possibly testosterone levels, people with hormone-sensitive conditions should use it cautiously and under supervision. For a broader approach to this topic, see our guide on adaptogens for hormonal balance and menstrual cycle.
• Peptic Ulcers: Ashwagandha can irritate the gastrointestinal tract, so people with active ulcers should avoid it or use it with extreme caution.
• Older Adults: While it can offer cognitive and strength benefits, older adults may be more sensitive to side effects, such as drowsiness. Starting with low doses is recommended.

At Kóre, we believe in a personalized and evidence-based approach for each individual. There is no one-size-fits-all solution.

How to Minimize Risks and Maximize Benefits

To enjoy the benefits of Ashwagandha while minimizing the risks of side effects, follow these recommendations based on science and our quality standards.

• Choose Certified Quality: Opt for high-quality standardized extracts, such as our Kóre Ashwagandha, which guarantees a consistent concentration of withanolides and is free of contaminants. Product purity is fundamental.
• Start with Low Doses: Begin with the minimum effective dose and gradually increase it if necessary, always under the guidance of a professional. This helps your body adapt and allows you to monitor any reactions.
• Take with Food: Consuming Ashwagandha with food can significantly reduce the possibility of stomach upset.
• Cycle its Use: Although there is no definitive evidence on the need to cycle Ashwagandha, some experts suggest taking periodic breaks (e.g., 5 days of use followed by 2 days off, or 8 weeks of use followed by 2 weeks off) to evaluate its continuous effect on your body.
• Listen to your Body: Pay attention to how you feel. If you experience persistent or unusual side effects, stop using it and consult your doctor.

To optimize your rest safely, you can explore alternatives in our article on natural sleep supplements, where we analyze science-backed options.

Conclusion: Your Well-being, Our Priority

Ashwagandha is a potent adaptogen with a favorable safety profile for most people when used correctly. However, like any bioactive substance, it is not without risks. Understanding Ashwagandha side effects and contraindications is essential to safely integrate it into your wellness routine. At Kóre Labs, we are committed to providing you with the highest quality products and the scientific information necessary for you to take control of your health with confidence. Remember that responsible supplementation is key to your rebirth.

If you are ready to experience the benefits of premium Ashwagandha, backed by science and formulated with the strictest quality standards, we invite you to discover our high-potency Ashwagandha extract. Your path to real balance begins today.

Scientific References

1. Chandrasekhar, K., Kapoor, J., & Anishetty, S. (2012). A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of Ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine, 34(3), 255–262. https://doi.org/10.4103/0253-7176.106022
2. National Institutes of Health (NIH). (2023). Ashwagandha. MedlinePlus. https://medlineplus.gov/druginfo/natural/953.html
3. Gannon, J. M., Forrest, P. E., & Roy, R. G. (2014). Subtle changes in thyroid indices during a placebo-controlled study of an extract of Withania somnifera in persons with bipolar disorder. Journal of Ayurveda and Integrative Medicine, 5(4), 241–245. https://doi.org/10.4103/0975-9476.146566
4. Kumar, A., & Kalonia, H. (2007). Effect of Withania somnifera on Sleep-Wake Cycle in Rats. Indian Journal of Pharmaceutical Sciences, 69(6), 801-804. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851362/