Medication · nitroimidazole antibacterial

Supplements and Metronidazole.

Every documented pair, every citation. Below: 2 documented pairs grouped by mechanism.

Metronidazole, sold under the brand name Flagyl, is classified under "nitroimidazole antibacterial" in the BNF.

Metronidazole is an antibiotic, usually taken as a short course, and the supplement questions people ask most when given one have reassuring answers. Probiotics are fine to take alongside it and lower the chance of antibiotic-related diarrhoea: space a bacterial probiotic, most Lactobacillus or Bifidobacterium products, about two hours from your dose, while Saccharomyces boulardii, which is a yeast, can be taken at the same time. Most everyday vitamins and minerals have no significant interaction with a short antibiotic course, so a daily multivitamin, vitamin D or vitamin C is generally not a concern. The combinations that genuinely matter are listed below with their evidence, and they tend to be specific: supplements that thin the blood, serotonergic supplements stacked on certain antibiotics, and supplements that are really a prescription drug in disguise, such as red yeast rice, which contains the statin lovastatin. The sensible step in every case is to tell your pharmacist what you already take, which is free at any UK community pharmacy.

Below are the 2 documented pairs we have explicitly assessed against Metronidazole in the Distil database: 2 green. The pairs cluster around 1 mechanism: Probiotic timing with antibiotics. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.

Documented interactions

Last reviewed 15 June 2026. Each interaction below is assessed against PubMed-indexed evidence.

Probiotic timing with antibiotics

Green Does Bifidobacterium longum 1714 interact with ?

Bifidobacterium longum 1714 and metronidazole are fine to use together, and the strain may lower the chance of antibiotic-related diarrhoea. Bifidobacterium longum 1714 is a live bacterium, so space it about two hours away from your metronidazole dose so the antibiotic does not reduce the live bacteria. The main exception is if your immune system is seriously weakened or you are critically ill in hospital, when any probiotic should be checked with your doctor first.

Evidence: Supported by human study data.

PMID 22570464 · PMID 20458757 · PMID 26756877 · BNF: Metronidazole

Green Does Probiotics interact with ?

Probiotics and metronidazole are fine to use together, and probiotics may lower the chance of antibiotic-related diarrhoea. If you take a bacterial probiotic (most Lactobacillus or Bifidobacterium products), space it about two hours away from your metronidazole dose so the antibiotic does not reduce the live bacteria. Saccharomyces boulardii is a yeast rather than a bacterium, so the antibiotic does not affect it and it can be taken at the same time. The main exception is if your immune system is seriously weakened or you are critically ill in hospital, when probiotics, particularly Saccharomyces boulardii, should be checked with your doctor first.

Evidence: Supported by human study data.

PMID 22570464 · PMID 20458757 · PMID 26756877 · BNF: Metronidazole

What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.

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For adults over 18. This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP or pharmacist, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.

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Distil's interactions database is reviewed and updated every quarter. We grade evidence transparently and publish our methodology, including every database change, at /about/methodology. This tool is information, not a substitute for clinical judgement. If you take medication and supplements together, your GP or pharmacist can review your full regimen against your medical history. If you want a full personalised stack reasoned against this same database, the Distil report is the next step up.