Metronidazole: what it treats and how to use it safely

Metronidazole (often known by brand names like Flagyl) is an antibiotic that fights anaerobic bacteria and some parasites. People take it for things like bacterial vaginosis, trichomoniasis, certain gut or dental infections, and skin problems such as rosacea (topical forms). It’s fast and effective when used the right way, but there are a few rules you should know before starting it.

How metronidazole works and common uses

Metronidazole attacks bacteria that don’t need oxygen to survive and certain single-celled parasites. For trichomoniasis, doctors often give a single 2 g dose or 500 mg twice daily for 7 days. For many bacterial infections, a typical oral dose is 500 mg twice daily for 7–10 days, but exact dose and duration depend on the infection. Topical gels or creams (0.75%–1%) are used for rosacea and applied once or twice daily. Always follow the prescriber’s instructions—different infections need different regimens.

Side effects, warnings, and interactions

Most people do fine, but expect possible nausea, a metallic taste, stomach upset, headaches, or mild dizziness. A longer course can cause peripheral neuropathy—numbness or tingling in hands or feet—so tell your doctor if that starts. Serious allergic reactions are rare, but seek help for rash, swelling, or breathing trouble.

Avoid alcohol while taking metronidazole and for 48 hours after the last dose. Drinking alcohol can cause flushing, nausea, vomiting, and rapid heart rate. Also watch for drug interactions: metronidazole can increase the effects of warfarin (risk of bleeding) and may affect some seizure medications. If you take blood thinners, seizure drugs, or have liver disease, talk to your provider before starting it.

If you’re pregnant or breastfeeding, ask your doctor. For some infections doctors still prescribe metronidazole in pregnancy when benefits outweigh risks, but your provider will choose the safest option. Don’t self-medicate.

Finish the full course, even if you feel better after a day or two. Stopping early can let bacteria survive and come back stronger. If symptoms don’t improve within a few days or they get worse, contact your prescriber—some infections need a different drug or longer treatment.

Practical tips: take pills with food to reduce stomach upset, keep topical gels away from eyes, and store medicines at room temperature. If you buy meds online, use a licensed pharmacy that requires a prescription—this avoids counterfeit or unsafe products.

Got side effects that worry you, or unsure about mixing metronidazole with other meds? Call your healthcare provider or pharmacist. They can check interactions, adjust doses, and recommend safer choices based on your health history.

Metronidazole is a useful tool when used correctly. Know the rules, follow the prescription, and reach out for help if anything doesn’t feel right.