Supplements and Erythromycin.
Erythromycin, sold under the brand names Erythroped, Erymax, is classified under "macrolide" in the BNF.
Erythromycin 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 3 documented pairs we have explicitly assessed against Erythromycin in the Distil database: 1 red, 1 amber, and 1 green. The pairs cluster around 3 mechanisms: CYP3A4 inhibition, CYP3A4 induction, and 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
CYP3A4 inhibition
Red yeast rice is a statin in disguise. It naturally contains monacolin K, the same molecule as the prescription statin lovastatin, and that statin is cleared by a liver enzyme called CYP3A4. Erythromycin blocks that enzyme, so taking the two together can push the statin in red yeast rice to much higher levels than intended and raise the risk of muscle damage, including the serious form called rhabdomyolysis. Do not combine them. If you need erythromycin, stop the red yeast rice for the course and speak to your GP or pharmacist.
CYP3A4 induction
St John's Wort speeds up a liver enzyme called CYP3A4, which helps clear erythromycin from the body. Taking the two together may lower the amount of erythromycin in your blood and could make the antibiotic less effective. If you are prescribed erythromycin, it is sensible to pause St John's Wort for the course and tell whoever prescribed it that you take it.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Probiotic timing with antibiotics
These 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 erythromycin 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.
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.
For adults over 18.
This tool gives evidence-graded information, not medical advice. Always discuss changes with your GP, pharmacist, or specialist before making them, especially if you take any medication, are pregnant, breastfeeding, or have a serious health condition.
How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologySomething missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.