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Potential Ashwagandha Side Effects (And Who Should Avoid It)
- 6 min read
- Updated October 2025
- By Purple Iris Team
If you’re considering ashwagandha, you’ve probably heard about its incredible benefits for stress, sleep, and overall balance. But you’re also asking the right question: “Is it safe for me?” It’s a question I hear all the time, and frankly, it’s the most important one you can ask before starting any new supplement.
You’re not looking for hype; you’re looking for honest, clear answers. What are the real risks? Who should absolutely avoid it? And how can you use it in a way that’s both effective and responsible? My goal here is to cut through the noise and give you a straightforward, science-backed guide to using ashwagandha safely.
I’ve spent countless hours digging into the clinical trials and safety data so you don’t have to. We’ll walk through the common (and usually mild) side effects, the less common but more serious concerns, and the critical situations where ashwagandha is a definite no-go. Let’s get you the clarity you need to make a confident decision.
Key Takeaways
- Stick to the proven safe dose: For most healthy adults, doses of 300–600 mg per day are well-tolerated and backed by clinical safety data [1, 2].
- Most side effects are mild: If they occur, the most common issues are minor digestive upset, drowsiness, and headaches, which often resolve on their own [4, 9]
- Some groups must avoid it: Do not take ashwagandha if you are pregnant/breastfeeding, have an autoimmune condition, have hyperthyroidism, or are scheduled for surgery.
- Long-term data is promising but limited: Studies show good safety for up to 6-12 weeks; be cautious with continuous use beyond that without medical guidance [4, 9].
Common Side Effects: What You Might Actually Feel
Let’s start with the good news. For the vast majority of healthy adults, ashwagandha is very gentle on the system, a fact that’s been proven over and over in high-quality studies [1, 2]. However, especially when you’re just starting or if you take a higher dose, you might experience a few mild, temporary effects.
Here’s what to watch for:
- Digestive Upset: This is the most common complaint I come across. Some people report mild stomach discomfort, nausea, or loose stools [4, 9]. I’ve found this often happens if the supplement is taken on an empty stomach.
- Drowsiness or Sedation: Ashwagandha is famous for its calming properties, which is fantastic for sleep. But for some, especially at higher doses, this can translate to feeling a bit too relaxed or drowsy during the day [4, 9].
- Headache: Though less common, a small number of people in clinical trials have reported mild headaches.
The key thing to remember is that these effects are typically temporary and often resolve as your body adjusts.
Less Common and More Significant Side Effects
Okay, now for the less frequent issues that you still need to have on your radar. While rare, ashwagandha can cause more significant changes in certain situations.
Thyroid Function
Research has shown that ashwagandha can increase thyroid hormone levels, specifically T3 and T4 [5]. For someone with an underactive thyroid (hypothyroidism), this might be helpful. But for those with an overactive thyroid (hyperthyroidism), it can be dangerous. Case reports have even documented thyrotoxicosis (dangerously high thyroid hormones) in some individuals [6, 7].
Lower Blood Pressure
Ashwagandha may reduce blood pressure [9], which can be great for some but problematic for those who already have low blood pressure. This could lead to dizziness or lightheadedness.
Menstrual Cycle Changes
There’s some evidence that the herb might influence reproductive hormones like FSH and LH, but controlled studies on this are still limited [11].
Medication Interactions: A Crucial Checklist
Herbs are powerful, and that means they can interact with medications. This is one of the most important parts of our conversation. You should be extremely cautious if you take any of the following:
- Sedatives (like benzodiazepines, barbiturates): Ashwagandha can amplify their drowsy effects [4, 9].
- Thyroid Medications: It can increase thyroid hormone activity, potentially leading to a hormone overload [6].
- Blood Pressure Medications: It can enhance their effects, possibly causing blood pressure to drop too low [9].
- Immunosuppressants: Because ashwagandha may boost immune activity, it could interfere with drugs designed to suppress the immune system [9].
- Diabetes Medications: It may lower blood sugar, which could cause it to drop too low when combined with diabetes drugs [9].
Who Should Absolutely Avoid Ashwagandha?
Let’s be crystal clear about this, because your safety is the number one priority. In certain situations, the potential risks outweigh the benefits. You should not take ashwagandha if you fall into any of these groups.
1. Pregnant or Breastfeeding Women
Do not take ashwagandha. Period. While some of the older fears may have been overstated, there simply isn’t enough robust safety data to justify any potential risk to you or your baby [8]. It’s not worth it.
2. People with Autoimmune Conditions
This includes conditions like multiple sclerosis (MS), lupus (SLE), and rheumatoid arthritis (RA). Ashwagandha may stimulate the immune system, which could potentially worsen symptoms of an autoimmune disease where the immune system is already overactive [9].
3. People with Thyroid Disorders
If you have hyperthyroidism (an overactive thyroid), avoid ashwagandha. It can increase thyroid hormone production and make your condition worse [5, 7].
4. People Preparing for Surgery
Stop taking ashwagandha at least two weeks before any scheduled surgery. Its potential effects on the nervous system could enhance the effects of anesthesia and other medications used during surgery [9].
Your Simple Safety Checklist
Knowledge is the first step, but action is what keeps you safe. Here is my simple, five-step checklist for using ashwagandha responsibly.
1. Start With a Personal Health Check
Before you begin, have an honest conversation with your doctor. Review your current health conditions and any medications you’re taking. This conversation is essential to make sure ashwagandha is a good fit for you.
2. Follow the Clinically-Proven Dosage
More is not better. The clinical studies that show both safety and effectiveness stick to a dose of 300-600 mg per day. Start with a lower dose (around 300 mg) and see how your body feels before considering any increase.
3. Listen to Your Body
Pay close attention to how you feel in the first few weeks. If you experience digestive upset, try taking it with food. If you feel too drowsy, consider taking it only in the evening. If side effects are persistent or concerning, stop taking it. Your body is your best guide.
4. Plan for Smart Long-Term Use
The strongest safety data we have is for use up to about 3–6 months. If you plan to use it for longer, it’s a good idea to work with your healthcare provider to monitor your progress and consider taking periodic breaks. This allows your body to reset and helps you stay aware of its effects [4, 9].
5. Insist on a High-Quality, Third-Party Tested Product
This final step is non-negotiable. Many “side effects” people experience can actually be caused by contaminants like heavy metals or undeclared ingredients in low-quality supplements. A pure product is a safer product.
Find the Right Ashwagandha Supplement For You
Looking for a Trusted Product?
I can’t overstate the importance of that last step. All the knowledge in the world doesn’t help if the product you choose is impure, under-dosed, or contaminated. A high-quality supplement is the foundation of a safe and effective experience.
This knowledge is only half the battle. Your final step is to ensure the product you choose is pure, potent, and free from the contaminants that can cause many of the side effects we’ve discussed. To help you, I’ve vetted the market’s top supplements and laid out the pros and cons of each based on purity, potency, third-party testing, and clinical backing.
Quick Picks: The Best Ashwagandha of 2025
The Practitioner’s Choice for Ultimate Purity: Pure Encapsulations – Trusted by functional medicine doctors and pharmacists for obsessive in-house and third-party testing that ensures zero contaminants and a potent, standardized dose you can trust implicitly.
The No-Nonsense Pick for Proven Performance: NutraBio – Delivers the clinically studied KSM-66® extract at the full 600 mg research dose with sports-nutrition-grade transparency and potency at an exceptional price.
The Smart Budget Buy for Everyday Calm: Nature’s Bounty – Combines clinically proven KSM-66® with L-Theanine for alert calm, making it a pharmacy-accessible, high-value option for taming daytime anxiety and sharpening focus.
The Holistic Choice for the Plant-Purist: Gaia – Features a full-spectrum blend of certified organic raw root and standardized extract for a gentler, traditional approach backed by radical seed-to-shelf transparency.
The Traditionalists’ Choice for Full-Spectrum Potency: Himalaya – Uniquely blends organic root powder, traditional extract, and solvent-free supercritical CO2 extraction to deliver the plant’s complete synergistic profile as Ayurvedic practice intended.
The Bottom Line
Ashwagandha is a powerful and well-studied adaptogen that is safe for most healthy people when used correctly. But safety isn’t accidental—it’s the result of being informed and intentional.
You now have the knowledge to use it responsibly. You know the proven dose, what to watch for, the absolute ‘no-go’ situations, and that the quality of your supplement is everything. By respecting both the power of the herb and your own unique biology, you can make a choice that is truly right for you [12].
The information in this article is for educational purposes only and is not a substitute for professional medical advice. Always consult with a qualified healthcare provider before starting any new supplement. These statements have not been evaluated by the Food and Drug Administration. This product/information is not intended to diagnose, treat, cure, or prevent any disease.”
Frequently Asked Questions
What are the most common side effects of ashwagandha?
The most common side effects are typically mild and temporary, including digestive upset (nausea, loose stools), drowsiness, and headaches. These often occur when first starting or at higher doses [4, 5].
Who should not take ashwagandha?
You should not take ashwagandha if you are pregnant or breastfeeding, have an autoimmune disease (like RA or lupus), have hyperthyroidism, or are preparing for surgery.
How long does it take for ashwagandha to work?
It’s not a quick fix. Most clinical studies show that consistent benefits for stress and sleep are typically noticed after 4-8 weeks of daily use.
Is ashwagandha safe for long-term use?
The strongest safety studies cover daily use for up to 6 months [4, 5]. While it may be safe for longer periods, it’s best to work with a healthcare provider to monitor its effects if you plan to use it beyond that timeframe.
Can ashwagandha affect my thyroid?
Yes. Ashwagandha can increase thyroid hormone levels (T3, T4, and TSH) [6]. This may be beneficial for people with hypothyroidism, but it can be dangerous for those with hyperthyroidism or taking thyroid medications. Always consult your doctor if you have any thyroid condition [6, 12].
Does ashwagandha interact with medications?
Yes, it can. It may interact with medications for thyroid, blood pressure, blood sugar, and sleep, as well as with immunosuppressants [9, 10, 12]. Always consult your doctor before using ashwagandha if you are taking any prescription medications.
References:
[1] Verma, N., Gupta, S. K., Tiwari, S., & Mishra, A. K. (2021). Safety of Ashwagandha Root Extract: A randomized, placebo-controlled study in healthy volunteers. Complementary Therapies in Medicine, 57, 102642. https://doi.org/10.1016/j.ctim.2020.102642
[2] 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
[3] Gopukumar, K., Thanawala, S., Somepalli, V., Rao, T. S. S., Thamatam, V. B., & Chauhan, S. (2021). Efficacy and safety of ashwagandha root extract on cognitive functions in healthy, stressed adults: A randomized, double-blind, placebo-controlled study. Evidence-Based Complementary and Alternative Medicine, 2021, 8254344. https://doi.org/10.1155/2021/8254344
[4] Tandon, N., & Yadav, S. S. (2020). Safety and clinical effectiveness of Withania somnifera (Linn.) Dunal root in human ailments. Journal of Ethnopharmacology, 255, 112768. https://doi.org/10.1016/j.jep.2020.112768
[5] Sharma, A. K., Basu, I., & Singh, S. (2018). Efficacy and safety of ashwagandha root extract in subclinical hypothyroid patients: A double-blind, randomized placebo-controlled trial. Journal of Alternative and Complementary Medicine, 24(3), 243–248. https://doi.org/10.1089/acm.2017.0183
[6] van der Hooft, C. S., Hoekstra, A., Winter, A., de Smet, P. A., & Stricker, B. H. (2005). Thyrotoxicosis following the use of ashwagandha. Nederlands Tijdschrift voor Geneeskunde, 149(47), 2637–2638.
[7] Patel, K., et al. (2022). Ashwagandha as a unique cause of thyrotoxicosis presenting with supraventricular tachycardia. Cureus, 14(4), e24350. https://doi.org/10.7759/cureus.24350
[8] Tallon, M., Koturbash, I., & Blum, J. (2025). A systematic and ethnobotanical review of ashwagandha’s (Withania somnifera) teratogenic and abortifacient potentials. Phytotherapy Research. https://doi.org/10.1002/ptr.70079
[9] Todorović, N., et al. (2025). Withania somnifera (ashwagandha) supplementation: A review of its mechanisms, health benefits, and role in sports performance. Nutrition & Metabolism, 22(1), Article 9. https://doi.org/10.1186/s12986-025-00902-7
[10] Dongre, S., Langade, D., & Bhattacharyya, S. (2015). Efficacy and safety of ashwagandha (Withania somnifera) root extract in improving sexual function in women: A pilot study. BioMed Research International, 2015, 284154. https://doi.org/10.1155/2015/284154
[11] Gopal, S., Ajgaonkar, A., Kanchi, P., Kaundinya, A., Thakare, V., Chauhan, S., & Langade, D. (2021). Effect of an ashwagandha (Withania somnifera) root extract on climacteric symptoms in women during perimenopause: A randomized, double-blind, placebo-controlled study. Journal of Obstetrics and Gynaecology Research, 47(12), 4414–4425. https://doi.org/10.1111/jog.15030
[12] Choudhary, D., Bhattacharyya, S., & Joshi, K. (2017). Body weight management in adults under chronic stress through treatment with ashwagandha root extract: A double-blind, randomized, placebo-controlled trial. Journal of Evidence-Based Complementary & Alternative Medicine, 22(1), 96–106. https://doi.org/10.1177/2156587216641830