If you are taking oral metronidazole or using metronidazole gel for an infection that is linked with sexual activity, such as trichomoniasis, pelvic inflammatory disease, or bacterial vaginosis you should not have sex for 7 days after single-dose therapy (or until you have completed the 7-day treatment regimen) and your symptoms have resolved. This will help reduce the risk of reinfection. If your sexual partners are also being treated, then abstain from sexual intercourse until they have finished treatment.

This means you should abstain from all forms of sex (including oral sex, vaginal sex, anal sex, and sex with a condom). This advice even applies to women being treated for bacterial vaginosis, which although not sexually transmitted, is linked with sexual activity. Researchers think that sex may change the bacterial environment in your vagina, making bacterial overgrowth more likely. Abstaining from sex during treatment gives the vaginal flora time to return to normal.

If you are taking metronidazole for other reasons, such as for an abdominal, bone, heart, lung, or skin infection, you do not need to abstain from sex.