Drug & supplement interaction

Uva Ursi + Conjugated Estrogens, Methyltestosterone

Conjugated Estrogens, Methyltestosterone brand name: Premarin with Methyltestosterone.

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

Conjugated Estrogens, Methyltestosterone falls into 3 drug categories that Uva Ursi can interact with; the most serious is rated moderate. Theoretically, uva ursi may decrease the metabolism of CYP3A4 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Uva Ursi and Conjugated Estrogens, Methyltestosterone

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Uva Ursi interacts with whole categories of medication. Conjugated Estrogens, Methyltestosterone falls into 3 of those categories, so it can interact with Uva Ursi in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 3

Why this applies to Conjugated Estrogens, Methyltestosterone

Conjugated Estrogens, Methyltestosterone falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Uva Ursi interacts with.

Theoretically, uva ursi may decrease the metabolism of CYP3A4 substrates.
In vitro, uva ursi appears to inhibit CYP3A4. This effect has not been reported in humans.
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

Here's the gist for your Premarin with Methyltestosterone. Both the estrogen and testosterone portions are partly processed by a liver enzyme called CYP3A4. In lab (test tube) studies, uva ursi seems to slow that enzyme down. If that happened in the body, your hormones could clear a little more slowly and build up, which might mean more side effects like breast tenderness, bloating, nausea, headaches, mood changes, or unwanted hair growth and acne from the testosterone side.

The important part: this has only been seen in lab dishes, never confirmed in real people, so I wouldn't lose sleep over it. Still, since uva ursi can also be hard on the liver, please run it by your pharmacist or doctor before starting it rather than just trying it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chauhan B, Yu C, Krantis A, et al. In vitro activity of uva-ursi against cytochrome P450 isoenzymes and P-glycoprotein. Can J Physiol Pharmacol. 2007;85(11):1099-107.
Moderate

GLUCURONIDATED DRUGS

2 of 3

Conjugated Estrogens, Methyltestosterone also falls under GLUCURONIDATED DRUGS.

Theoretically, uva ursi may increase levels of drugs metabolized by glucuronidation.
In vitro, uva ursi extract appears to strongly inhibit UDP-glucuronosyltransferase (UGT) 1A1 (UGT1A1). However, uva ursi extract does not appear to inhibit UGT1A1 in animal models. This effect has not been reported in humans.
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

Here's the gist with Premarin plus methyltestosterone and uva ursi. Your body clears estrogens partly through a process called glucuronidation, basically tagging the hormone so it can be removed. In a lab dish, uva ursi blocked one of those tagging enzymes (UGT1A1). If that happened in real life, your estrogen levels could drift a little higher than expected, which in theory might mean more spotting, breast tenderness, bloating, or nausea.

The honest part: this was only seen in test tubes, not in animals, and never in actual people. So I wouldn't lose sleep over it. Still, uva ursi can be hard on the liver and is meant only for short-term use. Before pairing them, check in with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Park JB, Kim D, Min JS, et al. Identification and characterization of in vitro inhibitors against UDP-glucuronosyltransferase 1A1 in uva-ursi extracts and evaluation of in vivo uva-ursi-drug interactions. Food Chem Toxicol. 2018;120:651-661. PubMed
Minor

P-GLYCOPROTEIN SUBSTRATES

3 of 3

Conjugated Estrogens, Methyltestosterone also falls under P-GLYCOPROTEIN SUBSTRATES.

Theoretically, uva ursi may alter the levels of drugs transported by P-glycoprotein.
In vitro, uva ursi appears to inhibit the multi-drug transporter protein, P-glycoprotein. This effect has not been reported in humans.
Severity Minor 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

Here's the gist with Premarin combined with methyltestosterone. There's a lab-only finding that uva ursi may block a transporter called P-glycoprotein, which acts like a doorman moving certain drugs around your body. If that doorman slows down, it's possible that slightly more of your hormone medication could stay in your system. In theory, that might nudge up estrogen-type effects like breast tenderness, bloating, nausea, or mood changes.

That said, I want to be honest with you: this has only been seen in a test tube, never in actual people, and it's rated as a minor concern. For most folks it's unlikely to cause trouble. Still, since uva ursi can stress the liver and is meant for short-term use, please check in with your pharmacist or doctor before pairing the two.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chauhan B, Yu C, Krantis A, et al. In vitro activity of uva-ursi against cytochrome P450 isoenzymes and P-glycoprotein. Can J Physiol Pharmacol. 2007;85(11):1099-107.

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

Uva Ursi Also Interacts With Other Medications

Uva Ursi has 739 moderate, 63 minor known drug interactions in our database — the Conjugated Estrogens, Methyltestosterone one above is among them. If you take anything else, check it against the full list below.

Moderate 739 Minor 63 No known interaction 2,028 (incl. Conjugated Estrogens, Methyltestosterone)
Taking anything else?

Check Another of Your Medications Against Uva Ursi

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

Everything else you take

See Every Supplement That Interacts With Conjugated Estrogens, Methyltestosterone

This page covers Uva Ursi only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Conjugated Estrogens, Methyltestosterone page lists 226 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 184 moderate · 36 minor.

From our pharmacist’s overview on the Conjugated Estrogens, Methyltestosterone page

“If you take conjugated estrogens with methyltestosterone (Premarin with Methyltestosterone), a hormone combination used for menopausal symptoms, read the six major-rated entries here before adding any supplement. Most of the 226 ingredients on file change how your body handles the hormones themselves.”

Reviewed by 2 · Jul 18, 2026

Open the Conjugated Estrogens, Methyltestosterone interaction page

One more smart check

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

We hold 1,423 real supplement products containing Uva Ursi, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Uva Ursi. Your product may carry other ingredients that interact with Conjugated Estrogens, Methyltestosterone too, on top of Uva Ursi — 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 Uva Ursi and Conjugated Estrogens, Methyltestosterone 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 Uva Ursi
Top 25%

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

29 days ago today
Medication Conjugated Estrogens, Methyltestosterone
Top half

#983 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 Uva Ursi

What is Uva Ursi?

Uva Ursi
  • Urinary tract infections
  • Urinary discomfort
  • Mild diuretic
  • Kidney stones
  • Skin conditions

Uva ursi is a traditional herb used mainly for urinary tract infections, and its leaves contain a compound called arbutin that may have antimicrobial effects in the urine. Evidence in people is limited, and because high doses or long-term use may be harmful to the liver and could be toxic, it should only be used short-term and with guidance from a healthcare professional. Avoid it during pregnancy and breastfeeding.

Read the full Uva Ursi monograph & all interactions
Keep checking

Other Drugs & Uva Ursi

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

0Major
739Moderate
63Minor
2,027No known interaction
739 Moderate 63 Minor 2,027 No interaction
Moderate

739 interactions

Showing 60 of 739 moderate interactions — see all 739 on the Uva Ursi page.

Minor

63 interactions

Showing 60 of 63 minor interactions — see all 63 on the Uva Ursi page.

No interaction 2,027 drugs checked — show the list

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

Showing the 60 most looked-up of 2,027 medications checked with no known interaction — see the full Uva Ursi list.

See the full Uva Ursi interactions page
See every supplement checked against Conjugated Estrogens, Methyltestosterone, 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
Uva Ursi monograph › Uses, safety, and every drug interaction in one place Conjugated Estrogens, Methyltestosterone supplement interactions › Every supplement checked against Conjugated Estrogens, Methyltestosterone, 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 Uva Ursi and Conjugated Estrogens, Methyltestosterone Together: Common Questions

Can you take Uva Ursi with Conjugated Estrogens, Methyltestosterone?
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.
Why are there 3 interactions listed for Uva Ursi and Conjugated Estrogens, Methyltestosterone?
Conjugated Estrogens, Methyltestosterone belongs to more than one drug category, and Uva Ursi interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Uva Ursi and Conjugated Estrogens, Methyltestosterone 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

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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.