Drug & supplement interaction

Myrcia + Levothyroxine, Liothyronine

Levothyroxine, Liothyronine brand name: Armour Thyroid.

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

Myrcia has a moderate interaction with Levothyroxine, Liothyronine. In vitro research shows that the Myrcia extract can inhibit thyroid peroxidase (TPO) activity, an enzyme involved in thyroid hormone biosynthesis.

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

Myrcia and Levothyroxine, Liothyronine

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

Moderate

LEVOTHYROXINE (Synthroid, others)

In vitro research shows that the Myrcia extract can inhibit thyroid peroxidase (TPO) activity, an enzyme involved in thyroid hormone biosynthesis. Theoretically, Myrcia might decrease the effectiveness of thyroid replacement therapy.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

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

If you take a thyroid medicine like Armour Thyroid (which combines levothyroxine and liothyronine), here is the simple version. Lab studies suggest Myrcia might block an enzyme called thyroid peroxidase, which your body uses to make its own thyroid hormone. In theory, that could nudge your thyroid levels lower and make your replacement therapy a little less effective, so you might notice symptoms creeping back like tiredness, feeling cold, weight gain, or sluggishness.

Keep this in perspective: this concern comes only from test-tube research, not from people, so it is theoretical. Still, since thyroid dosing is finicky and small changes matter, I would not add a Myrcia tea or supplement without checking with your doctor or pharmacist first. They can keep an eye on your TSH if needed.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ferreira AC, Neto JC, da Silva AC, et al. Inhibition of thyroid peroxidase by Myrcia uniflora flavonoids. Chem Res Toxicol 2006;19(3):351-55.

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

Myrcia Also Interacts With Other Medications

Myrcia has 2 moderate known drug interactions in our database — the Levothyroxine, Liothyronine one above is one of them. If you take anything else, check it against the full list below.

Moderate 2 No known interaction 2,828 (incl. Levothyroxine, Liothyronine)
Taking anything else?

Check Another of Your Medications Against Myrcia

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

Everything else you take

See Every Supplement That Interacts With Levothyroxine, Liothyronine

This page covers Myrcia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine, Liothyronine 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, Liothyronine page

“For anyone taking levothyroxine or liothyronine (Armour Thyroid), this list earns real caution, not just a passing glance. Most of these 50 ingredients pull in one of two directions.”

Reviewed by 2 · Jul 18, 2026

Open the Levothyroxine, Liothyronine interaction page

How much people look this up

Where Myrcia and Levothyroxine, Liothyronine 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 Myrcia
Steady interest

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

29 days ago today
Medication Levothyroxine, Liothyronine
Top 1%

#15 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 Myrcia

What is Myrcia?

  • Blood sugar support
  • Digestive upset and diarrhea
  • Mild urinary complaints
  • Astringent for the gut
  • Traditional 'pedra-hume-caa' folk remedy

Myrcia is a group of tropical shrubs and trees in the myrtle family, used in South American folk medicine—often as a tea—mainly for blood sugar and digestive complaints. Human evidence is very limited, so it should not replace proven treatments. Talk with your pharmacist or doctor before using it, especially if you have diabetes or take other medicines.

Read the full Myrcia monograph & all interactions
Keep checking

Other Drugs & Myrcia

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

0Major
2Moderate
0Minor
2,827No known interaction
2 Moderate 2,827 No interaction
Moderate

2 interactions

No interaction 2,827 drugs checked — show the list

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

Showing the 60 most looked-up of 2,827 medications checked with no known interaction — see the full Myrcia list.

See the full Myrcia interactions page
See every supplement checked against Levothyroxine, Liothyronine, 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
Myrcia monograph › Uses, safety, and every drug interaction in one place Levothyroxine, Liothyronine supplement interactions › Every supplement checked against Levothyroxine, Liothyronine, ranked by severity 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 Myrcia and Levothyroxine, Liothyronine Together: Common Questions

Can you take Myrcia with Levothyroxine, Liothyronine?
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 Myrcia and Levothyroxine, Liothyronine 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, Liothyronine and Myrcia?

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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.