Metronidazole
Tablet, gel or injection
Quick Summary
Metronidazole kills anaerobic bacteria and some parasites.
Medical Uses
How it's taken
Take it after food. Don't drink alcohol during the course and for 48 hours afterwards.
Take it for the full course, even if you feel better, unless your doctor tells you otherwise. Don't share antibiotics or keep leftovers.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Metallic taste
Common.
Nausea
And loss of appetite.
Dark urine
Harmless.
Interactions
Alcohol
Causes severe nausea, vomiting and flushing.
Warfarin
Increases bleeding risk.
Lithium
Levels can rise.
Critical Warnings
Alcohol
Avoid completely during and after treatment.
Numbness or tingling
With long courses: tell your doctor.
Severe allergic reaction
Black Box Warning: Swelling of the face or throat, difficulty breathing or a widespread rash: get emergency help.
Antibiotic resistance
Using antibiotics when they aren't needed makes them less effective for everyone.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Metronidazole: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Metronidazole: antibiotic medicine used to treat infections(opens in a new tab) · NHS