Herb & supplement monograph

Myrcia Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by ·Updated June 2026
What is this page for?

First and foremost: how Myrcia interacts with medications. The heart of this page is the interaction list — every drug Myrcia is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Myrcia is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Myrcia Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Myrcia drug interaction appears low for most people. Myrcia has only a handful of known interactions, none rated major, and the concern behind them rests on lab research rather than studies in people.

Interactions deserving the most attention

The one combination worth watching involves levothyroxine and other thyroid replacement medicines. Lab research shows Myrcia extract can block an enzyme the thyroid uses to make its hormone, so in theory Myrcia could make thyroid treatment work less well. Because thyroid doses are adjusted carefully using blood tests, even a modest change could matter for someone whose levels are tightly managed. This has not been confirmed in humans, so it remains a precaution rather than a proven problem.

What the rest of the list means

The small number of listed interactions reflects how little this plant group has been studied with medications, not proof that other combinations are safe or risky. What is known so far is theoretical, drawn from how Myrcia behaves in laboratory tests, and no human studies have yet shown a meaningful change in how any medication works.

Check your medications against Myrcia

Based on HelloPharmacist’s Myrcia interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Myrcia

3 medications have a known interaction with Myrcia, graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
LevothyroxineEltroxin, Estre, Euthyrox, Levo-T, Levolet, Levothroid +5 more› Levothyroxine SodiumErmez, Thyquidity, Tirosint-Sol› Levothyroxine, LiothyronineArmour Thyroid› "phentolamineOraVerse, Rogitine, Ryzumvi› 6-mercaptopurinePurinethol› Ado-trastuzumab EmtansineKadcyla› AbacavirZiagen› Abacavir Sulfate, Dolutegravir, LamivudineTriumeq› Abacavir, LamivudineEpzicom› AbaloparatideTymlos› AbametapirXeglyze› AbarelixPlenaxis› AbciximabReoPro› AbemaciclibVerzenio› Abiraterone› Abiraterone AcetateYonsa, Zytiga› AbrocitinibCibinqo› AcalabrutinibCalquence› AcamprosateCampral› AcarboseGlucobay, Prandase, Precose› AcebutololRhotral, Sectral› AcenocoumarolSintrom› AcepromazineAtravet› AcetaminophenChildren's Tylenol, Children's Tylenol Meltaways, Tylenol, Tylenol Ex Strength› Acetaminophen, AspirinGemnisyn› Acetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine› Acetaminophen, Brompheniramine, PhenylpropanolamineDimetapp Cold and Flu› Acetaminophen, ButalbitalAxocet, Bancap, Bucet, Butex Forte, Esgic CF, Orbivan CF +5 more› Acetaminophen, Butalbital, CaffeineEsgic, Esgic Plus, Fiogesic, Fioricet, Repan, Tecnal +1 more› Acetaminophen, Butalbital, Caffeine, CodeineEsgic with Codeine, Fioricet w/ Codeine›
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. 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.
  • Possible. 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
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Myrcia combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Myrcia affects

Every type of medication (drug category) Myrcia is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 1 drug category Myrcia interacts with
Levothyroxine (synthroid, Others)
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.

Likelihood Possible Evidence D
Monograph

Myrcia: Uses, Safety & Side Effects

Medically reviewed by · Reviewed June 2026 ·
The bottom line

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.

Family
Myrtaceae
Part used
Leaves (and sometimes bark)
Common forms
Tea, dried leaf, capsules, liquid extracts
People commonly use it for
  • Blood sugar support
  • Digestive upset and diarrhea
  • Mild urinary complaints
  • Astringent for the gut
  • Traditional 'pedra-hume-caa' folk remedy

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallLimited data

Human safety data are very limited, so caution is advised.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail
BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Myrcia is a large group of shrubs and trees in the myrtle family (Myrtaceae) that grow in tropical parts of Central and South America, especially Brazil. Several species have long been used in traditional medicine.

In folk practice, dried Myrcia leaves are often brewed into a tea. Some traditional preparations made from Myrcia have historically been called "pedra-hume-caa" or referred to as a kind of "vegetable insulin," reflecting their popular use for blood sugar concerns.

Today you may find Myrcia sold as a dried leaf, tea, capsule, or liquid extract, often marketed for blood sugar or digestive support.

How it works

Myrcia leaves contain plant compounds such as tannins, flavonoids, and other polyphenols. In test-tube and animal studies, some of these compounds show antioxidant activity and may affect enzymes involved in breaking down carbohydrates, which is one proposed reason for the traditional blood sugar use.

The astringent (drying, tightening) effect of tannins may also explain why Myrcia tea has traditionally been used for diarrhea.

It is important to know that these mechanisms are based mostly on laboratory and animal research. We do not have good evidence showing how—or whether—Myrcia works in the human body.

Effectiveness

Does Myrcia work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by .

Evidence overview · 1 use evaluated
1 Insufficient evidence
How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.
2Likely EffectiveGood evidence, though not yet conclusive.
3Possibly EffectiveSome evidence suggests a benefit.
4Possibly IneffectiveSome evidence it may not help.
5Likely IneffectiveFairly strong evidence it doesn’t help.
6IneffectiveStrong evidence it doesn’t work.
7Insufficient Reliable Evidence to RateToo little research to say either way.

For Myrcia, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 1 condition — evidence insufficient to rate
Insufficient Reliable Evidence To Rate Diabetes
Rating & evidence shown verbatim from Natural Medicines

Preliminary clinical research shows that consumption of an herbal tea containing Myrcia uniflora leaves 3 grams daily for 56 days does not improve fasting plasma glucose, insulin, or glycated hemoglobin levels when compared with placebo in patients with or without type 2 diabetes.

Sources Ref 27471

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

There is not much reliable safety information on Myrcia in humans. Because it is poorly studied, it is hard to know what doses or long-term use are safe.

People with diabetes should be especially careful, since Myrcia may affect blood sugar and could add to the effect of other treatments. Anyone with a chronic condition or who takes regular medicine should check with a pharmacist or doctor first.

Teas high in tannins can sometimes upset the stomach and may interfere with iron absorption if used heavily over time. During pregnancy and breastfeeding, avoid Myrcia because there is not enough information to consider it safe.

Side effects

Reported side effects are not well documented because of limited study. Based on its tannin content, possible effects include stomach upset, nausea, or constipation, especially with strong or frequent use.

As with any plant product, an allergic reaction is possible. Stop use and seek medical care if you notice rash, itching, swelling, or trouble breathing.

If you have diabetes, watch for signs of low blood sugar (shakiness, sweating, confusion) and check with your healthcare provider.

Dosing

There is no established standardized dose for Myrcia. Traditional use is usually as a tea made from the dried leaves, but amounts vary widely and are not backed by clinical research.

If you choose to try a commercial product, follow the directions on the label and do not exceed them. Because quality and strength differ between brands, it is wise to ask your pharmacist or doctor for guidance before starting.

Pregnancy & Breastfeeding

Myrcia & Pregnancy

Insufficient reliable information

Insufficient reliable information available; avoid using.

Myrcia & Breastfeeding

Insufficient reliable information

Insufficient reliable information available; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.

© 2026 Therapeutic Research Center

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

The 2 references that drive our Myrcia monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Russo EM, Reichelt AA, De Sa JR, et al. Clinical trial of Myrcia uniflora and Bauhinia forficata leaf extracts in normal and diabetic patients. Braz J Med Biol Res 1990;23(1):11-20.
  2. 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.
Keep reading

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.

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

Pharmacist Counseling Corner

Myrcia: Common Questions

What is Myrcia used for, and does it work?
People use Myrcia for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.
Does Myrcia interact with prescription medications?
Yes. We list 3 medications with a known interaction with Myrcia. Use the checker above to see how Myrcia interacts with a specific drug.
How are Myrcia interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Myrcia with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Myrcia interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
What is Myrcia used for?
It is used in traditional South American medicine mainly for blood sugar support and digestive problems like diarrhea, though human evidence for these uses is very limited.
Is Myrcia safe to take?
Its safety is not well studied in people, so it should be used cautiously and is not a substitute for proven treatments. Check with your pharmacist or doctor first.
Can I take Myrcia if I have diabetes?
Myrcia may affect blood sugar, so people with diabetes should be cautious and talk to their healthcare provider before using it, especially alongside diabetes medicines.
Can I use Myrcia while pregnant or breastfeeding?
No. There is not enough safety information, so it is best to avoid Myrcia during pregnancy and breastfeeding.

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

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