Lyng Pharmacy
Medicines A–Z · Antibiotic

Metronidazole

An antibiotic and antiprotozoal · Written by the Lyng Pharmacy team, based on NHS and BNF guidance · Updated August 2026
Also sold asFlagyl
Type of medicineAntibiotic
Available asTablets, oral suspension, gel, vaginal gel, suppositories
How you get itPrescription only

Metronidazole treats infections caused by anaerobic bacteria and certain parasites — dental abscesses, bacterial vaginosis, some gut and skin infections. Its most famous feature is the alcohol reaction, which is genuinely unpleasant and worth taking seriously.

What it is used for

Dental infections and abscesses, bacterial vaginosis, trichomoniasis, some gut infections including Clostridioides difficile, rosacea (as a gel), infected leg ulcers and pressure sores, and as part of Helicobacter pylori treatment.

Alcohol

Do not drink alcohol while taking metronidazole, or for 48 hours afterwards. The combination can cause flushing, severe nausea and vomiting, headache, palpitations and abdominal cramps. Watch out for alcohol in unexpected places — some cough medicines, mouthwashes and tonics contain it.

How to take it and what to expect

Take tablets with or just after food, swallowed whole with water, spaced evenly through the day. Finish the whole course.

A persistent metallic taste is very characteristic and resolves after the course. Furred tongue, nausea and loss of appetite are also common, as is darkened urine, which is harmless.

Report numbness or tingling in the hands or feet — this can occur with prolonged courses and should be assessed. Also report severe or bloody diarrhoea, a rash, or confusion and unsteadiness.

Tell your prescriber if you take warfarin — metronidazole raises the INR significantly — lithium, phenytoin or ciclosporin.

It can be used in pregnancy and breastfeeding where indicated, though high single doses are usually avoided.

Always read the label. This page is general information, not advice for your situation. Doses, warnings and interactions differ between products and between people. Check the leaflet inside your medicine, and ask our pharmacist if anything is unclear — that conversation is free and takes two minutes.

Questions about Metronidazole?

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Frequently asked questions

Why can I not drink alcohol on metronidazole?
The combination causes flushing, severe nausea and vomiting, headache and palpitations. Avoid alcohol during the course and for 48 hours afterwards.
Why does metronidazole give me a metallic taste?
It is a very common and harmless effect that resolves once the course finishes.
Does metronidazole affect warfarin?
Yes — it raises the INR significantly. Tell your anticoagulant clinic; you may need extra monitoring.
Is dark urine on metronidazole normal?
Yes, darkened urine is a harmless expected effect.

Related pages

Amoxicillin →Warfarin →Clotrimazole →All medicines A–Z →

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