Class landing · Antibiotics

Supplements and antibiotics.

What to space apart, what is safe, and the few combinations that matter, alongside ciprofloxacin, doxycycline and the macrolides.

Most antibiotic and supplement interactions are about timing, not danger. Quinolones (ciprofloxacin) and tetracyclines (doxycycline) bind to metal ions, so taken at the same time as calcium, iron, magnesium or zinc they form a complex the gut cannot absorb, and both the mineral and the antibiotic lose effect. The answer is spacing: take the mineral at least two hours apart from the antibiotic.

A few combinations are more than timing. Red yeast rice with a macrolide (clarithromycin, erythromycin) is the one to avoid: the macrolide blocks CYP3A4, which raises the lovastatin naturally present in red yeast rice and drives muscle-toxicity risk. St John’s Wort speeds up clearance of some antibiotics that are broken down by the CYP3A4 enzyme, reducing their effect. Melatonin levels tend to rise with ciprofloxacin, and high-dose vitamin A alongside doxycycline may add to a rare raised-pressure effect. Probiotics are generally fine and often helpful, just taken a couple of hours apart.

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

Your supplements

Add every supplement you take. Type a name and click each match to add it, as many as you like.

Your medications

Add all your medications, brand or generic. Type and click each match to add it.

Anything we should know? (optional)

Pick any that apply. We adjust the findings where context changes the answer.

I confirm I am 18 or over. This tool gives evidence-graded information, not medical advice; always discuss changes with your GP or pharmacist.

Add all the supplements and medications you take, then check them together in one go.

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How we decide

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 methodology

Your whole stack

Want this checked across everything you take?

This page checks the pairs you enter. The personalised Distil report goes further:

the same graded, cited interaction check across your whole stack, not just the pairs you thought to type in
where your current routine may be leaving you short of your goals
the evidence-backed compounds worth adding, and the ones worth dropping

It's a paid report: £79, or £49 for the first 25 customers. The interactions check is one section of it, and you can read a real one in full before you buy.

See a real sample report

Something 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.

Thanks, that's logged. We go through flagged items every week.

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.