What is metronidazole?

Metronidazole is a prescription-only medicine that treats certain infections caused by bacteria and parasites. This page relates specifically to its use for trichomoniasis.

How does it treat trichomoniasis?

Metronidazole enters the parasite responsible for trichomoniasis and disrupts the processes it needs to survive. This helps clear the infection when the medicine is taken correctly and the full course is completed.

Who can use this service?

This service is for adults aged 18 or over who have had a confirmed positive trichomoniasis result, or whose current sexual partner has had a confirmed diagnosis and who have been advised to seek treatment. Our prescribers will also consider your symptoms, allergies, medical conditions, pregnancy or breastfeeding status and current medicines.

When this is not the right starting point

Do not use symptoms alone to decide that you have trichomoniasis. Arrange testing through a sexual health clinic or GP if you do not have a confirmed result or confirmed-contact history.
You may also need clinic or GP assessment if you are pregnant or breastfeeding, have significant liver disease, are receiving dialysis, have a neurological condition, have severe symptoms, or have already completed treatment without improvement.

Partner care and other STI testing

Current sexual partners should be assessed and treated at the same time. Anyone diagnosed with trichomoniasis should also be offered testing for other STIs. Sexual health clinics can provide testing, confidential partner-notification support, and assessment where online treatment is not appropriate.

How to take metronidazole for trichomoniasis

If prescribed, take one 400mg tablet twice daily for seven days. Space the doses as evenly as you practically can and always follow your pharmacy label.

Swallow Whole: Swallow the tablet whole with water.
Take With Food: Take it during or just after food to reduce stomach upset.
Complete the Course: Finish all seven days, even if your symptoms improve sooner.
Do Not Share: Do not share your medicine with anyone else, including your partner.
No Alcohol: Do not drink alcohol during treatment or for 48 hours after your final dose.

If you miss a dose

Take the missed dose when you remember, unless it is nearly time for the next one. If it is nearly time, skip the missed dose and continue as normal. Do not take two doses together to make up for one you missed.

If you vomit

If you vomit soon after taking a dose, contact a pharmacist or prescriber for advice, because you may not have absorbed the medicine. Do not automatically take an extra tablet.

Sexual contact during treatment

Do not have sex until at least seven days after you and your current partner or partners have completed treatment and any advised follow-up.

Active ingredient

Each tablet contains 400mg of metronidazole.

Other ingredients

Inactive ingredients differ between manufacturers. Read the patient information leaflet supplied with your pack for the complete ingredient list, particularly if you have an allergy or intolerance. If you have a known allergy, tell us during your consultation so our clinicians can check the pack before we dispense.

Like all medicines, metronidazole can cause side effects, although not everyone gets them.

Common or recognised effects

Feeling sick or being sick
Diarrhoea or stomach discomfort
Reduced appetite
Headache
A metallic or unpleasant taste
A coated or furry tongue

Taking the tablets during or just after food may help with nausea or stomach discomfort.

Stop taking metronidazole and call 999 or go to A&E if you develop

Swelling of the face, lips, tongue or throat, difficulty breathing, or a widespread itchy rash
A severe rash, blistering or peeling skin
Confusion, hallucinations, seizures, a severe headache with neck stiffness, or difficulty speaking
Severe stomach pain, particularly if it spreads to your back
Yellowing of the skin or eyes

Contact your GP or call NHS 111 promptly if you develop

Unusual bruising, mouth ulcers, marked tiredness, changes in vision, or persistent tingling or numbness.

Read the patient information leaflet supplied with your medicine for the complete list of side effects. You can report a suspected side effect through the MHRA Yellow Card scheme.