Drug & supplement interaction

Testolone + Doxycycline

Doxycycline brand names: Vibra-Tabs, Vibramycin, Doryx, Monodox, Doxycin, and others.

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

Testolone has a moderate interaction with Doxycycline. Theoretically, concomitant use might have additive hepatotoxic effects.

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

Testolone and Doxycycline

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

Moderate

HEPATOTOXIC DRUGS

Why this applies to Doxycycline

Doxycycline falls under HEPATOTOXIC DRUGS — the group Testolone interacts with.

Theoretically, concomitant use might have additive hepatotoxic effects.
In a case report, a 52-year-old male was diagnosed with liver injury thought to be related to the use of products containing testolone. Also, elevated liver enzymes were commonly reported in a dose escalation study of testolone.
Severity Moderate Likelihood Possible Evidence B

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 concern with pairing Testolone (RAD-140) and doxycycline: both can be hard on the liver. Doxycycline is a well-known antibiotic, and while it's usually well tolerated, it can occasionally raise liver enzymes or, rarely, cause liver irritation. Testolone has its own track record of liver trouble, including a case report of liver injury and commonly elevated liver enzymes in a dosing study. Stacked together, the worry is that those stresses could add up.

This is mostly theoretical, based on weak evidence, but it's a real signal worth respecting. Watch for warning signs like yellowing skin or eyes, dark urine, belly pain, nausea, or unusual fatigue. Honestly, Testolone isn't an approved or safe product to begin with, so please talk with your pharmacist or doctor before combining anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. LoRusso P, Hamilton E, Ma C, et al. A first-in-human phase 1 study of a novel selective androgen receptor modulator (SARM), RAD140, in ER+/HER2- metastatic breast cancer. Clin Breast Cancer 2022;22(1):67-77. PubMed
  2. Barbara M, Dhingra S, Mindikoglu AL. Drug-induced liver injury associated with alpha bolic (RAD-140) and alpha elite (RAD-140 and LGD-4033). ACG Case Rep J 2020;7(6):e00409. 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

Testolone Also Interacts With Other Medications

Testolone has 369 moderate known drug interactions in our database — the Doxycycline one above is one of them. If you take anything else, check it against the full list below.

Moderate 369 No known interaction 2,461 (incl. Doxycycline)
Taking anything else?

Check Another of Your Medications Against Testolone

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

From our Q&A

Questions About Testolone or Doxycycline

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Testolone or Doxycycline, 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 Doxycycline

This page covers Testolone only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Doxycycline page lists 166 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Oleander (major) and Siberian Cocklebur (major).

By severity: 7 major · 139 moderate · 20 minor.

From our pharmacist’s overview on the Doxycycline page

“St. John's wort is the supplement I would flag first for anyone on doxycycline (Vibramycin, Doryx), because it can speed the antibiotic out of the body and leave an infection undertreated.”

Reviewed by 2 · Jul 18, 2026

Open the Doxycycline interaction page

One more smart check

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

We hold 9 real supplement products containing Testolone, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Testolone. Your product may carry other ingredients that interact with Doxycycline too, on top of Testolone — 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 Testolone and Doxycycline 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 Testolone
Top half

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

29 days ago today
Medication Doxycycline
Top 5%

#41 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 Testolone

What is Testolone?

  • Muscle building
  • Athletic performance and bodybuilding
  • Strength gains
  • Body recomposition (fat loss with muscle gain)

Testolone (RAD-140) is a synthetic experimental drug called a selective androgen receptor modulator (SARM), not a dietary supplement or herb, and it is not approved or proven safe for human use. It is illegally sold for muscle building, has been linked to serious harms including liver injury, and is banned in sports — it should not be taken outside of supervised clinical research.

Read the full Testolone monograph & all interactions
Medication

About Doxycycline

What Is Doxycycline Used For?

Brand names: Vibra-Tabs, Vibramycin, Doryx, Monodox, Doxycin, Doxy, Doxylin, Doxy-D, Periostat, Doxycycline Injection, Oracea, Xyrosa

Doxycycline belongs to the tetracycline family of antibiotics. It's prescribed for many types of bacterial infections, including respiratory tract infections, sexually transmitted infections (STIs), tick-borne illnesses like Rocky Mountain spotted fever, and eye infections. It's also used to help prevent malaria and, in some cases, as a helper treatment for severe acne.

In situations where penicillin-type antibiotics can't be used — due to allergy, for example — doxycycline can step in as an alternative. It should only be used for infections that are proven or strongly suspected to be caused by bacteria.

See full Doxycycline drug information
Keep checking

Other Drugs & Testolone

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

0Major
369Moderate
0Minor
2,460No known interaction
369 Moderate 2,460 No interaction
Moderate

369 interactions

Showing 60 of 369 moderate interactions — see all 369 on the Testolone page.

No interaction 2,460 drugs checked — show the list

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

Showing the 60 most looked-up of 2,460 medications checked with no known interaction — see the full Testolone list.

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

Can you take Testolone with Doxycycline?
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 Testolone and Doxycycline 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 Doxycycline and Testolone?

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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.