Ashwagandha - Synthroid (Levothyroxine) Interaction
Herbal: Ashwagandha
Also Known As: Withania somnifera, Ajagandha, Amangura, Asan, Asana, Asgand, Asgandh, Asgandha, Ashagandha, Ashvagandha, Ashwaganda, Ashwanga, Asoda, Asundha, Aswagandha, Avarada, Ayurvedic Ginseng, Cerise d'Hiver, Clustered Wintercherry, Ghoda Asoda
Drug: Levothyroxine
Brand names:
Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, Levo-T, Eltroxin, Estre, Levothyroxine, Novothyrox, Levolet
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Apr 27, 2025
Interaction Details
Levothyroxine is classified as belonging to the following category: Thyroid Hormone
Ashwagandha might increase the effects and adverse effects of thyroid hormone.
Concomitant use of ashwagandha with thyroid hormones may cause additive therapeutic and adverse effects. Preliminary clinical research and animal studies suggest that ashwagandha boosts thyroid hormone synthesis and secretion. In one clinical study, ashwagandha increased triiodothyronine (T3) and thyroxine (T4) levels by 41.5% and 19.6%, respectively, and reduced serum TSH levels by 17.4% from baseline in adults with subclinical hypothyroidism.
Interaction Rating
Likelihood of Occurrence
ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Pharmacist Analysis
As the effects of ashwagandha on thyroid hormone levels are unclear and may vary from person to person, if you have been diagnosed with hypothyroidism or other thyroid disorders, it is important to let your doctor know if you plan on taking ashwagandha.
- Dr. Brian Staiger, PharmDReferences
- Panda S, Kar A. Withania somnifera and Bauhinia purpurea in the regulation of circulating thyroid hormone concentrations in female mice. J Ethnopharmacol 1999;67:233-39.
- Panda S, Kar A. Changes in thyroid hormone concentrations after administration of ashwagandha root extract to adult male mice. J Pharm Pharmacol 1998;50:1065-68.
- Sharma AK, Basu I, Singh S. Efficacy and safety of Ashwagandha root extract in subclinical hypothyroid patients: a double-blind, randomized placebo-controlled trial. J Altern Complement Med. 2018 Mar;24(3):243-248.
Ashwagandha Overview
Ashwagandha, also known as Withania somnifera, is a herb commonly used in Ayurvedic medicine. It is native to India, and is used to treat a variety of conditions, including stress, anxiety, and insomnia. Some studies have also suggested that ashwagandha may have potential health benefits for conditions such as heart disease, diabetes, and cancer. However, more research is needed. Ashwagandha is often referred to as an adaptogenic herb, which is theorized to help the body to adapt to stress.
Levothyroxine Overview
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Levothyroxine is used to treat hypothyroidism (condition where the thyroid gland does not produce enough thyroid hormone). It is also used with surgery and radioactive iodine therapy to treat thyroid cancer. Levothyroxine is in a class of medications called hormones. It works by replacing thyroid hormone that is normally produced by the body.
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Without thyroid hormone, your body cannot function properly, which may result in poor growth, slow speech, lack of energy, excessive tiredness, constipation, weight gain, hair loss, dry, thick skin, increased sensitivity to cold, joint and muscle pain, heavy or irregular menstrual periods, and depression. When taken correctly, levothyroxine reverses these symptoms.
Ashwagandha - More Interactions
Ashwagandha interacts with 1326 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
| Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
| Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
| Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
| Unknown | No interactions have been reported or no interaction data is currently available. |
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Parts of this content are provided by the Therapeutic Research Center, LLC.
DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.
© 2021 Therapeutic Research Center, LLC
Drug descriptions are provided by MedlinePlus.
Ask A Pharmacist About Your Herbal Questions!
Dr. Brian Staiger, PharmD
In addition to being a clinical pharmacist specializing in pharmacotherapy, Dr. Brian Staiger is a registered herbalist through the American Herbalist Guild. He has combined his passion for pharmacy practice with the study of medical ethnobotany to improve patient care. Feel free to reach out about any of your herbal or medication questions!
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