Drug & supplement interaction

Probiotics + Ketoconazole

Ketoconazole brand name: Nizoral.

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

Probiotics has a minor interaction with Ketoconazole. Theoretically, taking antifungals with certain probiotics might decrease the effectiveness of probiotics.

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

Probiotics and Ketoconazole

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

Minor

ANTIFUNGALS

Why this applies to Ketoconazole

Ketoconazole falls under ANTIFUNGALS — the group Probiotics interacts with.

Theoretically, taking antifungals with certain probiotics might decrease the effectiveness of probiotics.
Some probiotics such as Saccharomyces boulardii are fungi. Therefore, simultaneously taking antifungals might kill a significant number of these organisms.
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 key thing to know: this interaction works in one direction only. It can knock down your probiotic, but it does not change how well ketoconazole fights your fungal infection. So your antifungal treatment stays just as effective.

Why does this happen? Some probiotics are actually yeasts, the best-known being Saccharomyces boulardii. Since ketoconazole is built to slow the growth of fungi and yeasts, it may kill off a good chunk of that probiotic if you take them at the same time. This is theoretical, based on how the drug works, and is considered minor. If you take a bacterial probiotic (like Lactobacillus), this concern doesn't really apply. When in doubt, ask your pharmacist to help you pick the right product.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Lewis SJ, Freedman AR. Review article: the use of biotherapeutic agents in the prevention and treatment of gastrointestinal disease. Aliment Pharmacol Ther 1998;12:807-22. 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

Probiotics Also Interacts With Other Medications

Probiotics has 182 moderate, 39 minor known drug interactions in our database — the Ketoconazole one above is one of them. If you take anything else, check it against the full list below.

Moderate 182 Minor 39 No known interaction 2,609 (incl. Ketoconazole)
Taking anything else?

Check Another of Your Medications Against Probiotics

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

From our Q&A

Questions About Probiotics 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 Probiotics 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 Probiotics 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 Probiotics as Part of a Dietary Supplement Product? Check It for Interactions

We hold 15 real supplement products containing Probiotics, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Probiotics. Your product may carry other ingredients that interact with Ketoconazole too, on top of Probiotics — 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 Probiotics 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 Probiotics
Top half

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

29 days ago today
Medication Ketoconazole
Steady interest

#1,440 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 Probiotics

What is Probiotics?

  • Digestive health and regularity
  • Antibiotic-associated diarrhea
  • Irritable bowel syndrome (IBS)
  • Vaginal and urinary health
  • Immune support
  • General gut microbiome balance

Probiotics are live 'friendly' microbes that may help certain digestive conditions, such as antibiotic-associated diarrhea and some cases of IBS, though benefits depend heavily on the specific strain and dose. They are generally well tolerated for healthy people but should be used with caution by those with serious illness or weakened immune systems. Talk with your pharmacist or doctor to pick a product that matches your goal.

Read the full Probiotics monograph & all interactions
Medication

About Ketoconazole

What Is Ketoconazole Used For?

Brand name: Nizoral

Ketoconazole is used in different ways depending on the product. Oral tablets treat serious fungal infections that affect the whole body, but only when other antifungal treatments have failed or can't be tolerated.

Topical products (cream, foam, shampoo) treat fungal and yeast-related skin and scalp conditions. Which condition each product treats depends on the specific product, so check the label on yours.

See full Ketoconazole drug information
Keep checking

Other Drugs & Probiotics

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

0Major
182Moderate
39Minor
2,608No known interaction
182 Moderate 39 Minor 2,608 No interaction
Moderate

182 interactions

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

Minor

39 interactions

No interaction 2,608 drugs checked — show the list

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

Showing the 60 most looked-up of 2,608 medications checked with no known interaction — see the full Probiotics list.

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

Can you take Probiotics with Ketoconazole?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Probiotics and Ketoconazole interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Ketoconazole and Probiotics?

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.