Is Ashwagandha Safe With Levothyroxine?

There is no study of ashwagandha and levothyroxine taken together, so nobody can say for certain. The concern is real, though. Some studies and case reports show ashwagandha can raise thyroid hormone levels, so on top of levothyroxine it could push your levels too high. The TGA also warns of a very rare but serious liver injury. If you take levothyroxine, talk to your GP or pharmacist before starting ashwagandha, and expect them to want to recheck your thyroid tests if you do.

Ashwagandha is everywhere, sold for stress, sleep and sometimes "thyroid support". If you live with Hashimoto's, an underactive thyroid or no thyroid, here is what the research actually shows.

Can ashwagandha raise thyroid hormone?

Sometimes, in some people. The evidence is real but small and inconsistent:

• In a small eight-week trial of 50 people in India whose TSH was mildly raised, ashwagandha moved their thyroid results toward normal compared with a dummy pill. That shows it can change thyroid hormone levels.
• When researchers pooled 23 trials in 2026, ashwagandha produced a small average rise in T4, with no clear change in TSH.
• A trial in 80 healthy adults found no change in thyroid results.
• At least four published case reports describe people whose thyroid swung to overactive while taking it.

So some studies show it nudges thyroid hormone up and others show no change. Nobody can predict who it will affect, and small on average does not mean small for everyone.

Why that matters on levothyroxine

There are no studies of ashwagandha and levothyroxine taken together, and no published case of someone becoming over-replaced on both. The worry is that both can raise thyroid hormone, so together they might push your levels too high. The Australian levothyroxine leaflets do not mention ashwagandha by name, but they ask you to tell your doctor about every vitamin or supplement you take, and they list a racing heart, anxiety, shakiness, poor sleep and weight loss as signs your thyroid hormone is too high.

If any of those start after you begin a new supplement, see your GP and ask for your thyroid tests to be checked. Do not change your dose yourself.

France's food-safety agency advises people with thyroid conditions not to take ashwagandha supplements, and US health authorities advise caution for people with thyroid or autoimmune conditions. There is no research on ashwagandha in people with Hashimoto's specifically.

The case that is usually told wrong

The best-known case report is often described as ashwagandha clashing with thyroid medication. It was not. It involved a 73-year-old with Hashimoto's who had stopped their thyroid medication two years earlier and taken ashwagandha instead. They ended up in hospital with a racing heart and a thyroid result that had swung to overactive, which settled once the ashwagandha was stopped.

The lesson is simpler, and more important: never swap prescribed thyroid medication for a supplement.

What about after a thyroidectomy?

The idea that ashwagandha raises thyroid hormone comes mainly from animal studies suggesting it stimulates the thyroid gland itself. If you have no thyroid, there may be less for it to act on, but no study has looked at this, so it is not safe to assume it makes no difference. The liver risk applies to everyone.

The liver warning

The TGA says liver injury from ashwagandha is very rare but can be serious. As of July 2026 it had received 11 reports of possible liver injury in Australia, with no deaths or transplants. Overseas, a small number of cases have led to liver failure. Most cases show up as jaundice and itching after weeks to months of use, and usually settle over one to five months after stopping.

The TGA advises stopping it and seeing a doctor if you notice:

• yellowing of the skin or eyes
• dark urine
• nausea or vomiting
• unusual tiredness or weakness
• tummy pain or loss of appetite

Anyone with current or past liver problems should avoid it altogether.

Other cautions

• Pregnancy. If you are pregnant or trying to be, do not take ashwagandha without talking to your doctor first. Many products are not required to carry a pregnancy warning, so do not rely on the label.
• Sedatives. Ashwagandha can cause drowsiness, so check with your pharmacist if you take sleeping tablets or other sedating medicines.
• It is not a food in Australia. Ashwagandha can be sold here as a listed medicine, but food regulators have not accepted it as safe in food.

Does it help stress or sleep?

Ashwagandha is mostly studied for stress and sleep. Small, short studies suggest it may help some people, but the evidence is low quality, the products vary a lot, and nobody knows how safe it is over the long term. A 2022 review in the Endocrine Society's journal found little to no evidence that it helps thyroid conditions. If stress or sleep is the problem, a GP is the better first stop, and with a thyroid condition there are extra reasons to check first. Our guides to anxiety and your thyroid and supplements to avoid with an underactive thyroid go further.

Questions to ask your GP or pharmacist

1. Is ashwagandha a sensible choice for me, given my thyroid condition and medication?
2. If I take it, when should my thyroid tests be rechecked?
3. Could it affect any of my other medicines?
4. What symptoms should make me stop it and call you?

Where ThyroBase fits

No supplement should replace thyroid medication or quietly change your thyroid levels. ThyroBase is a daily morning and evening nutrition powder for people living with Hashimoto's, an underactive thyroid or no thyroid, designed to sit alongside your thyroid medication, never instead of it. Here is who ThyroBase is, and is not, designed for.

Ashwagandha can raise thyroid hormone in some people, and nobody can predict who.

If you take levothyroxine, check first, and never take it instead of your medication.

Frequently asked questions

Is ashwagandha safe to take with levothyroxine?

There are no studies of the two taken together. Because ashwagandha can raise thyroid hormone in some people, it could push your levels too high on levothyroxine. Talk to your GP or pharmacist before starting it, and expect your thyroid tests to be rechecked if you do.

Does ashwagandha help an underactive thyroid?

There is little to no good evidence that it helps thyroid conditions. One small trial in people with a mildly raised TSH showed changes in thyroid results, but that is not a reason to use it as treatment. Never take it instead of prescribed thyroid medication.

Is ashwagandha safe with Hashimoto's?

There is no research on ashwagandha in people with Hashimoto's. France's food-safety agency advises people with thyroid conditions not to take it, and US health authorities advise caution with autoimmune conditions. Speak to your doctor before trying it.

What are the signs of liver problems from ashwagandha?

The TGA lists yellowing of the skin or eyes, dark urine, nausea, vomiting, unusual tiredness, weakness, tummy pain and loss of appetite. Stop it and see a doctor if you notice any of these. Liver injury is very rare but can be serious.

The honest takeaway

Ashwagandha is not proven to help your thyroid, it can raise thyroid hormone in some people, and it carries a very rare liver risk. None of that means you can never take it, but on levothyroxine it is a conversation to have with your GP or pharmacist first, followed by a thyroid test if you go ahead. And it is never a substitute for your medication.

ThyroBase is a nutritional supplement and is not intended to diagnose, treat, cure, or prevent any disease. It is designed to sit alongside your thyroid medication, not replace it. This article is general information, not medical advice. Never start, stop or change a supplement or prescription medication without speaking to your doctor or pharmacist first.

References

Sharma AK, Basu I, Singh S. Efficacy and safety of ashwagandha root extract in subclinical hypothyroid patients: a double-blind, randomized placebo-controlled trial. Journal of Alternative and Complementary Medicine. 2018;24(3):243-8.
Fornalik M, Malkiewicz A, Adamczak D, et al. Hormonal modulation with Withania somnifera: systematic review and meta-analysis of randomized-controlled trials. Planta Medica. 2026;92(8):790-805.
Verma N, Gupta SK, Tiwari S, Mishra AK. Safety of ashwagandha root extract: a randomized, placebo-controlled study in healthy volunteers. Complementary Therapies in Medicine. 2021;57:102642.
Gannon JM, Forrest PE, Roy Chengappa KN. 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. 2014;5(4):241-5.
Kamal HI, Patel K, Brdak A, et al. Ashwagandha as a unique cause of thyrotoxicosis presenting with supraventricular tachycardia. Cureus. 2022;14(3):e23494.
Hayashi M, Hamada H, Azuma SI, Hayashi K. Painless thyroiditis by Withania somnifera (ashwagandha). Cureus. 2024;16(3):e55352.
Larsen D, Singh S, Brito M. Thyroid, diet, and alternative approaches. Journal of Clinical Endocrinology and Metabolism. 2022;107(11):2973-81.
Björnsson HK, Björnsson ES, Avula B, et al. Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver International. 2020;40(4):825-9.
McIntyre D, Nguyen P, Kim Y, et al. Ashwagandha (Withania somnifera)-associated liver injury: a scoping review of clinical characteristics and safety considerations. Cureus. 2026;18(5):e109764.
Cheah KL, Norhayati MN, Husniati Yaacob L, Abdul Rahman R. Effect of ashwagandha (Withania somnifera) extract on sleep: a systematic review and meta-analysis. PLoS One. 2021;16(9):e0257843.
Akhgarjand C, Asoudeh F, Bagheri A, et al. Does ashwagandha supplementation have a beneficial effect on the management of anxiety and stress? A systematic review and meta-analysis of randomized controlled trials. Phytotherapy Research. 2022;36(11):4115-24.
Therapeutic Goods Administration. Medicines containing Withania somnifera (Withania, Ashwagandha): safety advisory. 22 February 2024; Withania somnifera (ashwagandha) and very rare risk of liver injury. Medicine Safety Update. 7 July 2026.
ANSES (French Agency for Food, Environmental and Occupational Health and Safety). Opinion 2021-SA-0077 on the risks of Withania somnifera preparations in food supplements. 2024.
Food Standards Australia New Zealand. Record of views formed in response to inquiries (novel foods). Updated July 2026.
Eutroxsig and Oroxine (levothyroxine sodium) Consumer Medicine Information and Product Information. Australian Commission on Safety and Quality in Health Care, Medicine Finder. 2025.
National Center for Complementary and Integrative Health. Ashwagandha. nccih.nih.gov. 2023.