Ashwagandha and Thyroid: Is It Safe with Levothyroxine?

Can You Take Ashwagandha with a Thyroid Condition?

Whether you can take ashwagandha depends on your specific thyroid diagnosis and your current prescription medication. Different thyroid conditions involve distinct risks. For some people, ashwagandha can raise hormone levels too far. For others, it presents a potential interaction with daily medication.

If you have subclinical hypothyroidism, one small trial found ashwagandha root extract shifted hormone levels. However, you should never use ashwagandha instead of prescribed medical treatment for hypothyroidism. That trial was a small pilot study, and it does not show that ashwagandha can replace standard care. If your lab results show elevated TSH, work with your doctor to establish an accurate diagnosis first.

If you take levothyroxine or Armour thyroid, taking ashwagandha requires direct medical supervision. Because ashwagandha can raise thyroid hormone levels, adding it to your daily routine could push your hormone levels too high. If your prescriber agrees, have TSH rechecked about 6 to 8 weeks after you start, the interval the American Thyroid Association gives for rechecking after any change in thyroid hormone dose. You can review Synthroid vs levothyroxine to understand your medication baseline.

If you have hyperthyroidism or Graves' disease, you should avoid ashwagandha completely. An overactive thyroid gland produces too much hormone already. Adding a supplement that can raise thyroid hormone levels increases the risk of thyrotoxicosis. Read our comparison of Hashimoto's vs Graves' to see how an overactive thyroid differs from an underactive one.

If you have Hashimoto's thyroiditis, NCCIH does not recommend ashwagandha. NCCIH's caution covers autoimmune and thyroid disorders; no specific mechanism is established. If your condition has progressed to underactive thyroid function and you take daily hormone replacement, the medication interaction rules apply. Check your thyroid antibodies and consult your physician before adding any new supplement.

What the Research Shows About Ashwagandha and Thyroid Hormones

Human research on ashwagandha and thyroid function consists of small clinical studies evaluating changes in circulating hormone levels. The primary trial on this topic was published by Sharma and colleagues in 2018. In this trial, 50 adults aged 18 to 50 with subclinical hypothyroidism took either 600 mg daily of ashwagandha root extract (300 mg twice daily) or a placebo for 8 weeks. Eligible participants had baseline TSH levels between 4.5 and 10 micro-international units per milliliter. After 8 weeks, ashwagandha improved TSH, T3, and T4 compared with placebo.

Side effects in the Sharma trial were mild and temporary. They occurred in 1 of 25 participants taking ashwagandha and 3 of 25 taking placebo. Still, the authors called it a pilot study, so the result needs confirming in larger trials. The study was brief. It did not examine whether the hormone changes persisted over long periods.

An earlier study published by Gannon and colleagues in 2014 observed thyroid changes during an 8-week trial in patients with bipolar disorder. Among the participants with abnormal baseline thyroid values, all 3 patients assigned to ashwagandha experienced increases in T4 levels of 7%, 12%, and 24%. In contrast, 6 of 7 participants in the placebo group had decreases in T4. Based on these findings, the study authors wrote that vigilance regarding hyperthyroidism may be warranted.

When Ashwagandha Pushes Thyroid Levels Too High

Documented medical case reports demonstrate that ashwagandha can trigger thyrotoxicosis, a condition where circulating thyroid hormone levels become excessive. According to the National Institutes of Health Office of Dietary Supplements (ODS), three case reports describe thyrotoxicosis in women aged 32 to 73 taking ashwagandha. One patient took an unusually high dose of 1,950 mg daily for more than 2 months. In all three instances, symptoms resolved after the individuals stopped taking the supplement. Two of those three cases are published in full.

In a report published by van der Hooft and colleagues in 2005, a 32-year-old woman developed thyrotoxicosis after increasing her daily ashwagandha dose. Her symptoms and abnormal thyroid numbers resolved after she discontinued the supplement. A separate case reported by Kamal and colleagues in 2022 involved a 73-year-old woman self-treating hypothyroidism with ashwagandha root extract for two years. She presented with a very fast heart rhythm, diagnosed as supraventricular tachycardia, and very low TSH. She fully recovered after stopping the extract.

These cases show that taking ashwagandha can push circulating hormone levels above normal boundaries. If you take ashwagandha and notice a racing or irregular heartbeat, stop the supplement and contact your doctor immediately. ODS warns that ashwagandha might interact with thyroid hormone medications, creating risks of hormone excess.

Why Some Thyroid Doctors Use It Anyway

Some physicians recommend ashwagandha to hypothyroid patients to support stress resilience and influence hormone levels. On this site, Dr. Teplitsky discusses this practice in his lecture on supplements that help the thyroid. He explains that ashwagandha is an adaptogen that reduces stress. He notes that lowering stress improves T4-to-T3 conversion, and he views ashwagandha as having separate positive effects on the thyroid. Dr. Teplitsky frequently recommends a thyroid-support product containing ashwagandha to his hypothyroid patients, a topic he covers further in his guide on thyroid supplements with medications. You can explore conversion mechanisms in his lecture on how T4 turns into T3.

The T4-to-T3 explanation is Dr. Teplitsky's clinical view; the trials on this page measured thyroid hormone levels and did not test conversion directly. Small trials show ashwagandha can raise thyroid hormone levels, which is one reason some clinicians, including Dr. Teplitsky on this site, use it for an underactive thyroid. Yet other health authorities view that same effect as a reason for caution.

International regulatory bodies have adopted strict positions. As noted in the ODS fact sheet, Denmark banned ashwagandha in 2023 after a 2020 risk assessment cited possible effects on thyroid hormones. France's Agency for Food, Environmental and Occupational Health & Safety (ANSES) recommended against its use in 2024 for people with endocrine disorders. In the United States, NCCIH explicitly advises that ashwagandha is not recommended for people with autoimmune or thyroid disorders.

If You Take It with Thyroid Medication

Combining ashwagandha with prescription thyroid medication requires strict medical oversight and routine blood monitoring. If you take levothyroxine, Synthroid, or desiccated thyroid extract like Armour, do not start ashwagandha on your own. Discuss the supplement with your prescribing clinician first. Bring the exact product packaging to your appointment so your doctor can verify the formulation.

When starting ashwagandha alongside prescription medication, plan your lab testing in advance. The American Thyroid Association notes that your doctor checks your blood 6 to 8 weeks after starting or changing your thyroid hormone dose. Schedule a follow-up blood test at that 6 to 8 week mark. Your doctor will test your TSH and free thyroid hormones to ensure your levels stay within range. You can track your target ranges using our guide on what is normal TSH.

Watch your physical symptoms carefully during those first two months. A racing or irregular heartbeat is a documented sign of hormone excess that requires prompt medical evaluation. Furthermore, ODS states that ashwagandha may have adverse effects on the liver and thyroid. While ashwagandha appears well tolerated for up to about 3 months in clinical trials, long-term safety remains unknown. If you and your doctor decide to try ashwagandha, set a stop date within three months (the studied window) and review it with your clinician.

If stress is the reason you are considering ashwagandha, our guide to lowering cortisol covers other options to discuss with your prescriber.

Ashwagandha Safety Across Different Thyroid Diagnoses

Safety considerations for ashwagandha depend on whether your thyroid is underactive, overactive, or medicated. The table below outlines how risks, regulatory guidance, and clinical recommendations align across common clinical situations.

Anyone with hyperthyroidism, Graves' disease, or active thyrotoxicosis should avoid ashwagandha completely, as should pregnant individuals and anyone taking thyroid replacement without medical supervision. What would change our answer would be large, multi-center randomized controlled trials that demonstrate long-term safety, stable hormone effects, and clear clinical outcomes in thyroid patients. Until such evidence exists, cautious medical oversight remains necessary.

If you are considering ashwagandha and thyroid health, schedule an appointment with your prescribing physician to review your current thyroid panel before introducing any new supplement.

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