Drug & supplement interaction

Lacticaseibacillus Casei + Letrozole

Letrozole brand name: Femara.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 13, 2026

The bottom line No known interaction

We found no known interaction between Lacticaseibacillus Casei and Letrozole 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

Lacticaseibacillus Casei and Letrozole

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 Letrozole and Lacticaseibacillus Casei 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.

Lacticaseibacillus Casei safety at a glance

Lacticaseibacillus... overall Use caution Generally well tolerated in healthy people, but caution is needed for those with weakened immune systems or serious illness.

Pregnancy Possibly Safe When used orally and appropriately. A combination of Lacticaseibacillus casei, Lactobacillus acidophilus, and Bifidobacterium bifidum has been used with apparen... Read the full pregnancy detail

Breastfeeding Use caution Likely low risk but not well studied; talk to your healthcare provider first.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Letrozole and Lacticaseibacillus Casei? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

How we checked

Why No Interaction Is Listed for Letrozole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Letrozole is filed under 4 classifications — including aromatase inhibitors, cytochrome p450 2c19 (cyp2c19) inhibitors, cytochrome p450 3a4 (cyp3a4) substrates. Lacticaseibacillus Casei has documented interactions with 1 drug class — the most serious being antibiotic drugs (moderate) — and none of Letrozole’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

Lacticaseibacillus Casei Does Interact With Other Medications

Lacticaseibacillus Casei has 182 moderate known drug interactions in our database — Letrozole 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. Letrozole)

Taking anything else?

Check Another of Your Medications Against Lacticaseibacillus Casei

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

What to actually watch for

What Lacticaseibacillus Casei Itself Has Been Linked To

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

Raised blood pressure / A higher chance of infection Worth acting on Additional detail
“Since Lacticaseibacillus casei 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 some cases of bacteremia, sepsis, splenic abscess, endocarditis, aortic dissection, necrotizing fasciitis, pancreatic necrosis, and meningoencephalitis.”

Lacticaseibacillus Casei · Natural Medicines adverse-effect record, reported in cardiovascular disease (cvd).
6 sources cited

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

112516. Russo A, Angeletti S, Lorino G, et al. A case of Lactobacillus casei bacteraemia associated with aortic dissection: is there a link?. New Microbiol 2010;33(2):175-8.

112520. Rahman A, Alqaisi S, Nath J. A Case of Lactobacillus casei endocarditis associated with probiotic intake in an immunocompromised patient. Cureus. 2023;15(4):e38049. PubMed

90282. Orkaby AR, Chen B, Iliaki EF, Sulis CA, Oates DJ. A curious case of Lactobacillus casei in a prosthetic joint: was it the yogurt? J Am Geriatr Soc. 2012;60(6):1177-8.

112514. de Seynes C, Dutronc H, Cremer P, Dupon M. Lactobacillus casei prosthetic joint infection. Med Mal Infect 2018;48(6):422-423. PubMed

96890. Topcuoglu S, Gursoy T, Ovali F, Serce O, Karatekin G. A new risk factor for neonatal vancomycin-resistant Enterococcus colonisation: bacterial probiotics. J Matern Fetal Neonatal Med. 2015;28(12):1491-4. PubMed
Stomach pain Additional detail
“Orally, taking Lacticaseibacillus casei in combination with other probiotics may cause gastrointestinal side effects including abdominal pain; however, these events are uncommon.”

Lacticaseibacillus Casei · Natural Medicines adverse-effect record, reported in pain.
1 source cited

90291. Shavakhi A, Tabesh E, Yaghoutkar A, Hashemi H, Tabesh F, Khodadoostan M,Minakari M, Shavakhi S, Gholamrezaei A. The effects of multistrain probiotic compound on bismuth-containing quadruple therapy for Helicobacter pylori infection: a randomized placebo-c

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

Special populations

Lacticaseibacillus Casei in Pregnancy & Breastfeeding

Pregnancy Possibly Safe

When used orally and appropriately. A combination of Lacticaseibacillus casei, Lactobacillus acidophilus, and Bifidobacterium bifidum has been used with apparent safety for 6 weeks, starting at 24-28 weeks' gestation.

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

Overlapping uses

What Letrozole Is Prescribed For, and What Lacticaseibacillus Casei Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Letrozole is a prescription medicine with approved uses on its FDA label. Lacticaseibacillus Casei is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Letrozole is prescribed for: Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer. Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

Lacticaseibacillus Casei has been studied for:

Cancer studied, not established Lacticaseibacillus Casei has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

Lacticaseibacillus Casei for cancer

Although there has been interest in using oral Lacticaseibacillus casei for cancer prevention or treatment, there is insufficient reliable information about the clinical effects of L. casei for this condition.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Letrozole on your own; if you are taking Lacticaseibacillus Casei for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Lacticaseibacillus Casei or Letrozole

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

This page covers Lacticaseibacillus Casei only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

How much people look this up

Where Lacticaseibacillus Casei and Letrozole 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 Lacticaseibacillus Casei

Top half

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

29 days ago today

Medication Letrozole

Top 5%

#51 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 Lacticaseibacillus Casei reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Lacticaseibacillus Casei and Letrozole records this page draws on were last updated July 11, 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 Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Lacticaseibacillus Casei

What is Lacticaseibacillus Casei?

Digestive health
Diarrhea (including antibiotic-related)
Immune support
Constipation
Gut microbiome balance

Lacticaseibacillus casei (formerly Lactobacillus casei) is a 'friendly' probiotic bacterium found in fermented foods and many supplements. It is most studied for digestive issues like diarrhea, where some evidence is encouraging, but results vary by strain and condition. It is generally well tolerated in healthy people, but those with weakened immune systems should check with a doctor first.

Lacticaseibacillus casei · Lactobacillaceae · Whole live bacteria (probiotic strain) · Capsules, tablets, powders, fermented dairy products like yogurt and probiotic drinks

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

Lacticaseibacillus Casei: dosing

There is no single official standardized dose for L. casei. 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.

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

Read the full Lacticaseibacillus Casei monograph & all interactions

Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information

Keep checking

Other Drugs & Lacticaseibacillus Casei

Browse every other medication we’ve checked against Lacticaseibacillus Casei — 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 Lacticaseibacillus Casei page.

No interaction 2,647 drugs checked — show the list

We also checked Lacticaseibacillus Casei 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 Lacticaseibacillus Casei list.

See the full Lacticaseibacillus Casei interactions page

See every supplement checked against Letrozole, ranked by severity

Evidence & sources

Lacticaseibacillus Casei References

The 10 references that drive our Lacticaseibacillus Casei 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.

Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.
Orkaby AR, Chen B, Iliaki EF, Sulis CA, Oates DJ. A curious case of Lactobacillus casei in a prosthetic joint: was it the yogurt? J Am Geriatr Soc. 2012;60(6):1177-8.
Shavakhi A, Tabesh E, Yaghoutkar A, Hashemi H, Tabesh F, Khodadoostan M,Minakari M, Shavakhi S, Gholamrezaei A. The effects of multistrain probiotic compound on bismuth-containing quadruple therapy for Helicobacter pylori infection: a randomized placebo-c
Karamali M, Dadkhah F, Sadrkhanlou M, et al. Effects of probiotic supplementation on glycaemic control and lipid profiles in gestational diabetes: a randomized, double-blind, placebo-controlled trial. Diabetes Metab 2016;42(4):234-41. PubMed
Topcuoglu S, Gursoy T, Ovali F, Serce O, Karatekin G. A new risk factor for neonatal vancomycin-resistant Enterococcus colonisation: bacterial probiotics. J Matern Fetal Neonatal Med. 2015;28(12):1491-4. PubMed
Badehnoosh B, Karamali M, Zarrati M, et al. The effects of probiotic supplementation on biomarkers of inflammation, oxidative stress and pregnancy outcomes in gestational diabetes. J Matern Fetal Neonatal Med. 2018 May;31(9):1128-1136.
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
de Seynes C, Dutronc H, Cremer P, Dupon M. Lactobacillus casei prosthetic joint infection. Med Mal Infect 2018;48(6):422-423. PubMed
Russo A, Angeletti S, Lorino G, et al. A case of Lactobacillus casei bacteraemia associated with aortic dissection: is there a link?. New Microbiol 2010;33(2):175-8.
Rahman A, Alqaisi S, Nath J. A Case of Lactobacillus casei endocarditis associated with probiotic intake in an immunocompromised patient. Cureus. 2023;15(4):e38049. 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 Lacticaseibacillus Casei and Letrozole Together: Common Questions

Is it safe to take Lacticaseibacillus Casei with Letrozole?

We do not list a known interaction between Lacticaseibacillus Casei and Letrozole. 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.

Are Lacticaseibacillus Casei and Letrozole used for the same thing?

They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Lacticaseibacillus Casei in each. That is a conversation for your prescriber, especially if Letrozole is being adjusted to a target.

How was the Lacticaseibacillus Casei and Letrozole combination checked?

Interactions in our licensed database are recorded against drug classes. Letrozole is filed under 4 classifications, and Lacticaseibacillus Casei has documented interactions with 1 drug class — none of Letrozole'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 Lacticaseibacillus Casei interact with any other medications?

Yes. Lacticaseibacillus Casei has 182 documented drug interactions in our database — Letrozole 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 Letrozole interact with any supplements?

Yes. Letrozole has documented interactions with 142 supplements in our database — Lacticaseibacillus Casei is not one of them. The Letrozole 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

Lacticaseibacillus Casei monograph Uses, safety profile, and every drug interaction in one place Letrozole drug information The full plain-English guide to this medication Letrozole supplement interactions Every supplement checked against Letrozole, 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 10 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Lacticaseibacillus Casei?

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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.