Drug & supplement interaction

Tiratricol + Levothyroxine

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

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Tiratricol has a major interaction with Levothyroxine. Concomitant use of tiratricol with thyroid hormones may have additive effects.

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

Tiratricol and Levothyroxine

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

Major

THYROID HORMONE

Why this applies to Levothyroxine

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

Concomitant use of tiratricol with thyroid hormones may have additive effects.
Tiratricol is a thyroid hormone and should only be used under medical supervision.
Severity Major 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 simple version: your levothyroxine (Synthroid and the others) is replacement thyroid hormone, dosed carefully so you get just the right amount. Tiratricol acts like another thyroid hormone (it switches on the same receptors as your natural T3), so taking it alongside your levothyroxine basically stacks thyroid activity on top of thyroid activity. The two effects add together.

That can push you into too much thyroid, which looks like a racing or pounding heartbeat, anxiety, shakiness, trouble sleeping, sweating, weight loss, and over time risks to your heart and bones. Tiratricol has also been flagged by the FDA as unsafe and has shown up illegally in some weight-loss products. Please don't combine it with your levothyroxine. Talk with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mueller-Gaertner HW, Schneider C. 3,5,3'-Triiodothyroacetic acid minimizes the pituitary thyrotrophin secretion in patients on levo-thyroxine therapy after ablative therapy for differentiated thyroid carcinoma. Clin Endocrinol (Oxf) 1988;28:345-51.

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

Tiratricol Also Interacts With Other Medications

Tiratricol has 15 major, 209 moderate 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.

Major 15 Moderate 209 No known interaction 2,606 (incl. Levothyroxine)
Taking anything else?

Check Another of Your Medications Against Tiratricol

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

From our Q&A

Questions About Tiratricol 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 Tiratricol 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 Tiratricol 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), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate), Ascophyllum Nodosum (moderate) and Ashwagandha (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

How much people look this up

Where Tiratricol 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 Tiratricol
Steady interest

#1,053 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 Tiratricol

What is Tiratricol?

  • Weight loss
  • Fat burning
  • Boosting metabolism
  • Bodybuilding and cutting
  • Thyroid-related supplementation

Tiratricol (also called TRIAC) is a powerful synthetic thyroid hormone metabolite, not a natural herb, and it has been illegally added to some weight-loss and bodybuilding supplements. It can cause serious heart and thyroid problems, and the U.S. FDA has warned consumers not to use products containing it. It is not a safe or approved dietary supplement, and you should avoid it.

Read the full Tiratricol 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 or supplements the thyroid hormone your body isn't making enough of. It's used for hypothyroidism — an underactive thyroid — in adults, children, and even newborns, whether the cause is the thyroid gland itself, the pituitary gland, or the hypothalamus in the brain.

It's also used alongside surgery and radioiodine treatment in people with certain types of thyroid cancer, to help suppress the hormone that can stimulate cancer growth. It is not meant for weight loss, treating benign thyroid nodules in people who have enough iodine, or for hypothyroidism during recovery from a temporary condition called subacute thyroiditis.

See full Levothyroxine drug information
Keep checking

Other Drugs & Tiratricol

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

15Major
209Moderate
0Minor
2,605No known interaction
15 Major 209 Moderate 2,605 No interaction
Major

15 interactions

Moderate

209 interactions

Showing 60 of 209 moderate interactions — see all 209 on the Tiratricol page.

No interaction 2,605 drugs checked — show the list

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

Showing the 60 most looked-up of 2,605 medications checked with no known interaction — see the full Tiratricol list.

See the full Tiratricol 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
Tiratricol 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 Tiratricol and Levothyroxine Together: Common Questions

Can you take Tiratricol with Levothyroxine?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Tiratricol and Levothyroxine interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

Still Have a Question About Levothyroxine and Tiratricol?

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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.