Drug & supplement interaction

Ashwagandha + Levothyroxine

Levothyroxine brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, and others.

Moderate Interaction
Medically reviewed by · Updated October 2026
The bottom line Moderate

Ashwagandha has a moderate interaction with Levothyroxine. Ashwagandha might increase the effects and adverse effects of thyroid hormone.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Ashwagandha and Levothyroxine

Here is the interaction we found between these two, with the evidence behind it.

Moderate

THYROID HORMONE

Why this applies to Levothyroxine

Levothyroxine falls under THYROID HORMONE — the group Ashwagandha interacts with.

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.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to keep an eye on with these two. Levothyroxine is a replacement thyroid hormone, basically a measured dose meant to bring you to just the right level. Ashwagandha appears to nudge your own thyroid to make and release a bit more hormone on its own. So taking them together can stack on top of each other, and your total thyroid activity may end up running higher than you and your doctor planned for.

If your levels creep too high, you might notice a racing or pounding heart, feeling jittery or anxious, trouble sleeping, shakiness, sweating, or unintended weight loss. The evidence here comes from small studies, so it's not a guarantee, but it's worth respecting. Please don't change your dose on your own. Let your pharmacist or doctor know if you want to add ashwagandha, since they may want to recheck your thyroid labs.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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. PubMed
  2. 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. PubMed
  3. 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. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • 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.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Ashwagandha Also Interacts With Other Medications

Ashwagandha has 917 moderate, 455 minor known drug interactions in our database — the Levothyroxine one above is one of them. If you take anything else, check it against the full list below.

Moderate 917 Minor 455 No known interaction 1,458 (incl. Levothyroxine)
Taking anything else?

Check Another of Your Medications Against Ashwagandha

Covers the 2,830 medications we’ve checked against Ashwagandha. Pick one to open its full report.

From our Q&A

Questions About Ashwagandha or Levothyroxine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Ashwagandha or Levothyroxine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Levothyroxine

This page covers Ashwagandha only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

By severity: 2 major · 39 moderate · 9 minor.

From our pharmacist’s overview on the Levothyroxine page

“Levothyroxine replaces a hormone your body measures in tiny amounts, so small shifts in its blood level show up in how you feel, and I treat this list with genuine care. Nearly everything on it does one of two things: blocks the pill from being absorbed in the gut, the way everyday minerals like calcium do by binding it into complexes,…”

Reviewed by 2 · Jul 18, 2026

Open the Levothyroxine interaction page

One more smart check

Taking Ashwagandha as Part of a Dietary Supplement Product? Check It for Interactions

We hold 4,964 real supplement products containing Ashwagandha, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ashwagandha. Your product may carry other ingredients that interact with Levothyroxine too, on top of Ashwagandha — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Ashwagandha and Levothyroxine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Ashwagandha
Top 5%

#31 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levothyroxine
Top 10

#2 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Ashwagandha

What is Ashwagandha?

Ashwagandha
  • Stress and anxiety
  • Sleep problems
  • Fatigue and low energy
  • Athletic performance
  • General well-being (adaptogen)

Ashwagandha is an Ayurvedic herb most often taken to help with stress, anxiety, and sleep, and some small studies suggest it may help, though the evidence is still limited. It is generally well tolerated for short-term use in healthy adults, but it should be avoided in pregnancy and used cautiously by people with thyroid or liver problems. Talk with your pharmacist or doctor before starting it.

Read the full Ashwagandha monograph & all interactions
Medication

About Levothyroxine

What Is Levothyroxine Used For?

Brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, Levo-T, Eltroxin, Estre, Levothyroxine, Novothyrox, Levolet

Levothyroxine replaces thyroid hormone when your body does not make enough. The oral products (tablets, capsules and oral solution) treat hypothyroidism, which can be present from birth or develop later. They are also used alongside surgery and radioiodine therapy for thyrotropin-dependent well-differentiated thyroid cancer.

Levothyroxine Sodium injection (given intravenously) is used only for myxedema coma, a life-threatening emergency from severe hypothyroidism. Age ranges differ by product. For example, Tirosint capsules are labeled for adults and children 6 years and older.

See full Levothyroxine drug information
Keep checking

Other Drugs & Ashwagandha

Browse every other medication we’ve checked against Ashwagandha — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
917Moderate
455Minor
1,457No known interaction
917 Moderate 455 Minor 1,457 No interaction
Moderate

917 interactions

Showing 60 of 917 moderate interactions — see all 917 on the Ashwagandha page.

Minor

455 interactions

Showing 60 of 455 minor interactions — see all 455 on the Ashwagandha page.

No interaction 1,457 drugs checked — show the list

We also checked Ashwagandha against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,457 medications checked with no known interaction — see the full Ashwagandha list.

See the full Ashwagandha interactions page
See every supplement checked against Levothyroxine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

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

Keep exploring
Ashwagandha monograph › Uses, safety, and every drug interaction in one place Levothyroxine supplement interactions › Every supplement checked against Levothyroxine, ranked by severity Levothyroxine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Ashwagandha and Levothyroxine Together: Common Questions

Can you take Ashwagandha with Levothyroxine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Ashwagandha and Levothyroxine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Levothyroxine and Ashwagandha?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.