Drug & supplement interaction

Lactobacillus Gasseri + Fulvestrant

Fulvestrant brand name: Faslodex.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Lactobacillus Gasseri and Fulvestrant in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Lactobacillus Gasseri and Fulvestrant

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Fulvestrant and Lactobacillus Gasseri in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Lactobacillus Gasseri safety at a glance

Lactobacillus Gass... overall Use caution Generally well tolerated in healthy adults, but evidence is limited and some people should avoid it.
Pregnancy Use caution Not enough reliable safety data; use only with a doctor's guidance.
Breastfeeding Use caution Limited safety information, so check with your doctor before using.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Fulvestrant and Lactobacillus Gasseri? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Fulvestrant

Interactions in our licensed database are recorded against drug classes, not just single drug names. Fulvestrant is filed under a single classification. Lactobacillus Gasseri has documented interactions with 1 drug class — the most serious being antibiotic drugs (moderate) — and none of Fulvestrant’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Lactobacillus Gasseri Does Interact With Other Medications

Lactobacillus Gasseri has 182 moderate known drug interactions in our database — Fulvestrant isn’t one of them. If you take anything else, check it against the full list below.

Moderate 182 No known interaction 2,648 (incl. Fulvestrant)
Taking anything else?

Check Another of Your Medications Against Lactobacillus Gasseri

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

What to actually watch for

What Lactobacillus Gasseri Itself Has Been Linked To

This is not an interaction — nothing below involves Fulvestrant. It is the side-effect record for Lactobacillus Gasseri on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Lactobacillus Gasseri, this list is the first place to look. One entry is worth acting on rather than waiting out — marked below.

  • A higher chance of infection Worth acting on Additional detail

    “Since Lactobacillus gasseri preparations contain live and active microorganisms, there is some concern that they might cause pathogenic infection in some patients. Some lactobacilli species have been isolated in cases of bacteremia, sepsis, splenic abscess, endocarditis, necrotizing fasciitis, pancreatic necrosis, and meningoencephalitis.”

    Lactobacillus Gasseri · Natural Medicines adverse-effect record, reported in cirrhosis.

    6 sources cited
    1. 107543. Rossi F, Amadoro C, Gasperi M, Colavita G. Lactobacilli infection case reports in the last three years and safety implications. Nutrients. 2022;14(6):1178. PubMed
    2. 110917. Ranchal P, Gupta R, Goldberg R, A Lobo S, Pascual A, El Khoury MY. Penicillin-sensitive Lactobacillus jensenii bacteremia. Am J Ther 2021;28(2):e250-e252. PubMed
    3. 110918. Grazioli-Gauthier L, Rigamonti E, Leo LA, Martinetti Lucchini G, Lo Priore E, Bernasconi E. Lactobacillus jensenii mitral valve endocarditis: Case report, literature review and new perspectives. IDCases 2022;27:e01401. PubMed
    4. 110920. Toprak NU, Bozan T, Yilmaz S, Buyukbayrak EE, Tigen ET. Polymicrobial bacteremia due to Lactobacillus jensenii and Veillonella montpellierensis in a pregnant patient; case report and review of literature. Anaerobe 2022;75:102576. PubMed
    5. 110921. Chazan B, Raz R, Shental Y, Sprecher H, Colodner R. Bacteremia and pyelonephritis caused by Lactobacillus jensenii in a patient with urolithiasis. Isr Med Assoc J 2008;10(2):164-5.
    6. 112579. Ramos-Coria D, Canto-Losa J, Carrillo-Vázquez D, Carbajal-Morelos L, Estrada-León R, Corona-Rodarte E. Lactobacillus gasseri liver abscess and bacteremia: a case report. BMC Infect Dis 2021;21(1):518. PubMed

Everything above comes from the Natural Medicines adverse-effect record for Lactobacillus Gasseri — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Fulvestrant’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Fulvestrant column appears here.

Everything else you take

See Every Supplement That Interacts With Fulvestrant

This page covers Lactobacillus Gasseri only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Fulvestrant page lists 1 supplement it has a documented interaction with, worst first, each one explained.

The most serious there right now: Dhea (moderate).

By severity: 1 moderate.

Open the Fulvestrant interaction page

One more smart check

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

We hold 852 real supplement products containing Lactobacillus Gasseri, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lactobacillus Gasseri. Even though Lactobacillus Gasseri itself has no known interaction with Fulvestrant, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Lactobacillus Gasseri and Fulvestrant 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 Lactobacillus Gasseri
Top 25%

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

29 days ago today
Medication Fulvestrant
Steady interest

#1,667 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Lactobacillus Gasseri reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Lactobacillus Gasseri and Fulvestrant records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Lactobacillus Gasseri

What is Lactobacillus Gasseri?

  • Digestive health
  • Weight and belly fat management
  • Vaginal and urinary health
  • Bloating and gut discomfort
  • General immune support

Lactobacillus gasseri is a 'friendly' probiotic bacterium found naturally in the human gut, mouth, and vaginal tract, and in some fermented foods. Early research suggests it may help with digestion, weight management, and vaginal health, but the evidence is limited and far from conclusive. It is generally well tolerated in healthy people, but anyone who is pregnant, breastfeeding, or has a weakened immune system should talk to a pharmacist or doctor first.

Lactobacillus gasseri · Lactobacillaceae · Live bacterial cells (probiotic strain) · Capsules, tablets, powders, fermented dairy products, and combination probiotic supplements

An interaction check asks whether these two react with each other — it does not ask whether Lactobacillus Gasseri is a good idea for someone in your situation. Here is what our Lactobacillus Gasseri record says about it on its own.

Lactobacillus Gasseri: dosing

There is no official standardized dose of L. gasseri. Probiotic amounts are usually measured in colony-forming units (CFUs), and products vary widely.The best approach is to follow the directions on the product label and not exceed the recommended amount.

From our Lactobacillus Gasseri monograph — the full record covers uses, side effects and every documented interaction.

Read the full Lactobacillus Gasseri monograph & all interactions
Medication

About Fulvestrant Injection

What Is Fulvestrant Injection Used For?

Brand name: Faslodex

Fulvestrant injection treats hormone receptor (HR)-positive advanced breast cancer in postmenopausal women. It can be used alone for women who have not yet had endocrine (hormone-blocking) therapy, or for women whose cancer has grown despite endocrine therapy.

It is also used in combination with other medicines — palbociclib, abemaciclib, or ribociclib — for HR-positive, HER2-negative advanced or metastatic breast cancer in women whose disease has progressed after endocrine therapy. Fulvestrant injection combined with ribociclib may also be used as an initial hormone-based treatment in this setting.

Most-Reported Side Effects for Fulvestrant

From FAERS, the FDA’s public side-effect reporting system (32,843 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Malignant neoplasm progression 4,229 reports
Fatigue 4,182 reports
Nausea 3,029 reports
Diarrhea 2,623 reports
Neutropenia 2,485 reports
See full Fulvestrant Injection drug information
Keep checking

Other Drugs & Lactobacillus Gasseri

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

0Major
182Moderate
0Minor
2,647No known interaction
182 Moderate 2,647 No interaction
Moderate

182 interactions

Showing 60 of 182 moderate interactions — see all 182 on the Lactobacillus Gasseri page.

No interaction 2,647 drugs checked — show the list

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

Showing the 60 most looked-up of 2,647 medications checked with no known interaction — see the full Lactobacillus Gasseri list.

See the full Lactobacillus Gasseri interactions page
See every supplement checked against Fulvestrant, ranked by severity
Evidence & sources

Lactobacillus Gasseri References

The 12 references that drive our Lactobacillus Gasseri 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. Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.
  2. Ramachandran L, Dontaraju VS, Patel K. Lactobacillus-associated spontaneous bacterial peritonitis in a liver cirrhosis patient on probiotics. Cureus. 2020;12(12):e11896. PubMed
  3. Rossi F, Amadoro C, Gasperi M, Colavita G. Lactobacilli infection case reports in the last three years and safety implications. Nutrients. 2022;14(6):1178. PubMed
  4. Ranchal P, Gupta R, Goldberg R, A Lobo S, Pascual A, El Khoury MY. Penicillin-sensitive Lactobacillus jensenii bacteremia. Am J Ther 2021;28(2):e250-e252. PubMed
  5. Grazioli-Gauthier L, Rigamonti E, Leo LA, Martinetti Lucchini G, Lo Priore E, Bernasconi E. Lactobacillus jensenii mitral valve endocarditis: Case report, literature review and new perspectives. IDCases 2022;27:e01401. PubMed
  6. Toprak NU, Bozan T, Yilmaz S, Buyukbayrak EE, Tigen ET. Polymicrobial bacteremia due to Lactobacillus jensenii and Veillonella montpellierensis in a pregnant patient; case report and review of literature. Anaerobe 2022;75:102576. PubMed
  7. Chazan B, Raz R, Shental Y, Sprecher H, Colodner R. Bacteremia and pyelonephritis caused by Lactobacillus jensenii in a patient with urolithiasis. Isr Med Assoc J 2008;10(2):164-5.
  8. Ramos-Coria D, Canto-Losa J, Carrillo-Vázquez D, Carbajal-Morelos L, Estrada-León R, Corona-Rodarte E. Lactobacillus gasseri liver abscess and bacteremia: a case report. BMC Infect Dis 2021;21(1):518. PubMed
  9. Elikowski W, Malek-Elikowska M, Lisiecka M, Bodora A, Wisniewska K, Oko-Sarnowska Z. Lactobacillus gasseri endocarditis on the aortic valve bioprosthesis - a case report. Pol Merkur Lekarski 2017;43(257):220-223.
  10. Esquibel A, Dababneh AS, Palraj BR. Lactobacillus gasseri causing bilateral empyema. Case Rep Infect Dis 2017;2017:4895619.
  11. Tleyjeh IM, Routh J, Qutub MO, Lischer G, Liang KV, Baddour LM. Lactobacillus gasseri causing Fournier's gangrene. Scand J Infect Dis 2004;36(6-7):501-3. PubMed
  12. Dickgiesser U, Weiss N, Fritsche D. Lactobacillus gasseri as the cause of septic urinary infection. Infection 1984;12(1):14-6. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Lactobacillus Gasseri and Fulvestrant Together: Common Questions

Is it safe to take Lactobacillus Gasseri with Fulvestrant?
We do not list a known interaction between Lactobacillus Gasseri and Fulvestrant. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
How was the Lactobacillus Gasseri and Fulvestrant combination checked?
Interactions in our licensed database are recorded against drug classes. Fulvestrant is filed under 1 classification, and Lactobacillus Gasseri has documented interactions with 1 drug class — none of Fulvestrant's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Lactobacillus Gasseri interact with any other medications?
Yes. Lactobacillus Gasseri has 182 documented drug interactions in our database — Fulvestrant is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Fulvestrant interact with any supplements?
Yes. Fulvestrant has documented interactions with 1 supplement in our database — Lactobacillus Gasseri is not one of them. The Fulvestrant interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Lactobacillus Gasseri monograph Uses, safety profile, and every drug interaction in one place Fulvestrant Injection drug information The full plain-English guide to this medication Fulvestrant supplement interactions Every supplement checked against Fulvestrant, 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 References The 12 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Fulvestrant and Lactobacillus Gasseri?

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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.