Drug & supplement interaction

Bacillus Subtilis + Ketoconazole

Ketoconazole brand name: Nizoral.

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 Bacillus Subtilis and Ketoconazole 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. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Bacillus Subtilis and Ketoconazole

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 Ketoconazole and Bacillus Subtilis 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.

Bacillus Subtilis safety at a glance

Bacillus Subtilis overall Use caution Generally well tolerated in healthy adults, but quality and safety can vary by product and strain.
Pregnancy Use caution There is not enough safety data, so it is best to avoid unless a doctor advises otherwise.
Breastfeeding Use caution Limited safety information exists, so check with your doctor before use.

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

Still wondering about combining Ketoconazole and Bacillus Subtilis? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Ketoconazole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Ketoconazole is filed under 8 classifications — including antifungals, cytochrome p450 2c19 (cyp2c19) inhibitors, cytochrome p450 2c9 (cyp2c9) inhibitors. Bacillus Subtilis has documented interactions with 1 drug class — the most serious being antibiotic drugs (moderate) — and none of Ketoconazole’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

Bacillus Subtilis Does Interact With Other Medications

Bacillus Subtilis has 182 moderate known drug interactions in our database — Ketoconazole 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. Ketoconazole)
Taking anything else?

Check Another of Your Medications Against Bacillus Subtilis

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

What to actually watch for

No Interaction Found — But Data Suggests Bacillus Subtilis and Ketoconazole May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Itching Additional detail

    Bacillus Subtilis

    “Orally, itching and redness were reported rarely.”

    Bacillus Subtilis · Natural Medicines adverse-effect record, reported in pruritus.

    1 source cited
    1. 110848. Hanifi A, Culpepper T, Mai V, et al. Evaluation of Bacillus subtilis R0179 on gastrointestinal viability and general wellness: a randomised, double-blind, placebo-controlled trial in healthy adults. Benef Microbes 2015;6(1):19-27. PubMed

    Ketoconazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Ketoconazole. Read the label on DailyMed ›

  • Diarrhea Additional detail

    Bacillus Subtilis

    “Orally, diarrhea has been reported rarely.”

    Bacillus Subtilis · Natural Medicines adverse-effect record, reported in diarrhea.

    1 source cited
    1. 110846. Freedman KE, Hill JL, Wei Y, et al. Examining the gastrointestinal and immunomodulatory effects of the novel probiotic Bacillus subtilis DE111. Int J Mol Sci 2021;22(5):2453. PubMed

    Ketoconazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Ketoconazole. Read the label on DailyMed ›

  • Headache Additional detail

    Bacillus Subtilis

    “Orally, one case of headache was reported in a clinical trial.”

    Bacillus Subtilis · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 110847. Lefevre M, Racedo SM, Denayrolles M, et al. Safety assessment of Bacillus subtilis CU1 for use as a probiotic in humans. Regul Toxicol Pharmacol 2017;83:54-65. PubMed

    Ketoconazole

    Listed in the ADVERSE REACTIONS section of the FDA label for Ketoconazole. Read the label on DailyMed ›

Reported for Bacillus Subtilis but not commonly for Ketoconazole: kidney problems and a higher chance of infection.

Effects for Ketoconazole come from the ADVERSE REACTIONS section of its FDA label; effects for Bacillus Subtilis come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

From our Q&A

Questions About Bacillus Subtilis or Ketoconazole

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

This page covers Bacillus Subtilis only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ketoconazole page lists 182 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 · 135 moderate · 41 minor.

From our pharmacist’s overview on the Ketoconazole page

“Ketoconazole (Nizoral) is already hard on the liver, so treat its 182 interacting supplements with genuine care, starting with the six rated major. Most of the list runs through CYP3A4, the liver enzyme ketoconazole strongly blocks, so it can raise levels of over a hundred herbal ingredients, while grapefruit pushes ketoconazole itself…”

Reviewed by 2 · Jul 18, 2026

Open the Ketoconazole interaction page

One more smart check

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

We hold 786 real supplement products containing Bacillus Subtilis, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Bacillus Subtilis. Even though Bacillus Subtilis itself has no known interaction with Ketoconazole, 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 Bacillus Subtilis and Ketoconazole 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 Bacillus Subtilis
Top 25%

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

29 days ago today
Medication Ketoconazole
Steady interest

#2,214 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 Bacillus Subtilis reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Bacillus Subtilis and Ketoconazole 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 Bacillus Subtilis

What is Bacillus Subtilis?

  • Digestive health and bloating
  • Diarrhea support
  • Immune support
  • Gut microbiome balance

Bacillus subtilis is a spore-forming probiotic bacterium found in soil and some fermented foods, and it is used mainly to support gut health and digestion. Early research is promising for certain digestive and immune uses, but evidence is still limited and not strong enough to make firm claims. Talk to a pharmacist or doctor before using it, especially if you have a weak immune system.

Bacillus subtilis · Bacillaceae · Live bacterial cells and spores (probiotic strains) · Capsules, tablets, powders, and multi-strain probiotic blends

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

Bacillus Subtilis: dosing

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

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

Read the full Bacillus Subtilis monograph & all interactions
Medication

About Ketoconazole

What Is Ketoconazole Used For?

Brand name: Nizoral

Ketoconazole 2% shampoo and foam are used to treat tinea versicolor (also called pityriasis versicolor) — a fungal infection caused by Pityrosporum orbiculare (also known as Malassezia furfur), a yeast that naturally lives on the skin.

This infection creates light or dark patches, most often on the trunk, neck, arms, and upper thighs. Even after the fungus is cleared, those skin patches may take months to return to their normal color — that's normal, and depends on your skin type and sun exposure. Tinea versicolor can also come back, since the fungus lives on healthy skin even when there's no active infection.

Most-Reported Side Effects for Ketoconazole

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Pruritus 984 reports
Fatigue 975 reports
Nausea 873 reports
Rash 858 reports
Diarrhea 814 reports
See full Ketoconazole drug information
Keep checking

Other Drugs & Bacillus Subtilis

Browse every other medication we’ve checked against Bacillus Subtilis — 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 Bacillus Subtilis page.

No interaction 2,647 drugs checked — show the list

We also checked Bacillus Subtilis 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 Bacillus Subtilis list.

See the full Bacillus Subtilis interactions page
See every supplement checked against Ketoconazole, ranked by severity
Evidence & sources

Bacillus Subtilis References

The 10 references that drive our Bacillus Subtilis 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. Lampropoulos PK, Gkentzi D, Tzifas S, Dimitriou G. Neonatal sepsis due to Bacillus subtilis. Cureus 2021;13(9):e17692. PubMed
  3. La Jeon Y, Yang JJ, Kim MJ, et al. Combined Bacillus licheniformis and Bacillus subtilis infection in a patient with oesophageal perforation. J Med Microbiol 2012;61(Pt 12):1766-1769. PubMed
  4. Wallet F, Crunelle V, Roussel-Delvallez M, Fruchart A, Saunier P, Courcol RJ. Bacillus subtilis as a cause of cholangitis in polycystic kidney and liver disease. Am J Gastroenterol 1996;91(7):1477-8.
  5. Velasco E, Martins CA, Tabak D, Bouzas LF. "Bacillus subtilis" infection in a patient submitted to a bone marrow transplantation. Rev Paul Med 1992;110(3):116-7.
  6. Kato A, Yoshifuji A, Komori K, et al. A case of Bacillus subtilis var. natto bacteremia caused by ingestion of natto during COVID-19 treatment in a maintenance hemodialysis patient with multiple myeloma. J Infect Chemother 2022;28(8):1212-1215. PubMed
  7. Freedman KE, Hill JL, Wei Y, et al. Examining the gastrointestinal and immunomodulatory effects of the novel probiotic Bacillus subtilis DE111. Int J Mol Sci 2021;22(5):2453. PubMed
  8. Lefevre M, Racedo SM, Denayrolles M, et al. Safety assessment of Bacillus subtilis CU1 for use as a probiotic in humans. Regul Toxicol Pharmacol 2017;83:54-65. PubMed
  9. Hanifi A, Culpepper T, Mai V, et al. Evaluation of Bacillus subtilis R0179 on gastrointestinal viability and general wellness: a randomised, double-blind, placebo-controlled trial in healthy adults. Benef Microbes 2015;6(1):19-27. PubMed
  10. Tokano M, Tarumoto N, Imai K, et al. A case of bacterial meningitis caused by Bacillus subtilis var. natto. Intern Med. 2022. Epub ahead of print.

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 Bacillus Subtilis and Ketoconazole Together: Common Questions

Is it safe to take Bacillus Subtilis with Ketoconazole?
We do not list a known interaction between Bacillus Subtilis and Ketoconazole. 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.
Do Bacillus Subtilis and Ketoconazole have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Bacillus Subtilis and Ketoconazole combination checked?
Interactions in our licensed database are recorded against drug classes. Ketoconazole is filed under 8 classifications, and Bacillus Subtilis has documented interactions with 1 drug class — none of Ketoconazole'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 Bacillus Subtilis interact with any other medications?
Yes. Bacillus Subtilis has 182 documented drug interactions in our database — Ketoconazole 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 Ketoconazole interact with any supplements?
Yes. Ketoconazole has documented interactions with 182 supplements in our database — Bacillus Subtilis is not one of them. The Ketoconazole 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

Bacillus Subtilis monograph Uses, safety profile, and every drug interaction in one place Ketoconazole drug information The full plain-English guide to this medication Ketoconazole supplement interactions Every supplement checked against Ketoconazole, 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 Ketoconazole and Bacillus Subtilis?

Our pharmacists answer your medication & supplement questions — free.

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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.