Often mild
- Metallic taste
- Nausea
- Headache
- Darkened urine
- Loss of appetite
Rx required in the US, UK, and Canada
Metronidazole
Also called Flagyl. Nitroimidazole antibiotic and antiprotozoal.
Anaerobic bacterial infections, bacterial vaginosis, trichomoniasis, and some dental and abdominal infections. Not a sinus or ordinary UTI drug.
Last reviewed . RxNorm 6922. SNOMED CT substance 372602008.
What metronidazole treats
Primary uses clinicians actually reach for this drug for. Local resistance and your own history can take a use off the list.
- Bacterial vaginosis and trichomoniasis, on a regimen matched to the person. Partners with trichomoniasis need their own care.
- Anaerobic infections in the abdomen, pelvis, and some dental infections, as an adjunct to source control.
- Some C. difficile regimens and some H. pylori combinations. Those are specific diagnoses, not a use for ordinary diarrhea or stomach pain.
Clinicians use several oral and vaginal products. A tablet, an extended-release tablet, and a vaginal gel are not substitutes for one another.
What it does not treat
- Colds, flu, COVID-19, and sinus infections
- Ordinary bladder infections. Nitrofurantoin or another urinary drug is the usual conversation.
- Viral or watery diarrhea that has not been diagnosed
- A tooth abscess with no dental plan
- A hangover. Alcohol is part of the warning, not part of the treatment.
Forms, dosing examples, and how to take it
Forms
- Immediate-release tablets, commonly 250 mg and 500 mg
- Capsules
- Extended-release tablets, which must not be crushed
- Vaginal gel and cream, and topical gel. Those are local products, not oral doses.
Adult examples
CDC and product labeling use different schedules for BV, trichomoniasis, and anaerobic infections. The right one is a prescription. A single 2 gram dose is not automatically the modern choice, especially for women with trichomoniasis.
| Situation | Example adults may see on a label or guideline | Limit |
|---|---|---|
| Bacterial vaginosis, a usual oral regimen clinicians write | 500 mg by mouth twice daily for 7 days | Vaginal metronidazole is an alternative product with its own instructions. Do not swallow the gel. |
| Trichomoniasis | CDC has preferred a 7-day oral course for women. A one-time dose is still used in some situations, including many male partners. | Do not pick the one-time dose from memory. Partners need treatment, and a repeat test is often advised. |
| Anaerobic infections | Often 500 mg every 6 to 8 hours, or another labeled schedule, for a course the prescriber sets | Source control, such as drainage or dental care, still has to happen. |
Food, minerals, and administration
- Take immediate-release tablets with food if the label or your stomach requires it. Extended-release products have their own food rule. Do not crush them.
- Do not drink alcohol during treatment and for at least 3 days after the last dose. The label warns of a disulfiram-like reaction: flushing, pounding heart, nausea, vomiting, and headache.
- Do not take metronidazole if you take disulfiram, or if you have taken it recently. The combination can cause psychotic reactions. The usual gap cited is 2 weeks.
- Warfarin effect can rise. Mouthwash, cough syrup, and sauces can contain alcohol. Ask the pharmacist before you assume a product is safe.
- A metallic taste is common and unpleasant. It is not, by itself, an emergency.
Can an online doctor prescribe metronidazole?
Yes only inside the narrow band below. The same visit is supposed to refuse the drug outside that band.
When a prescription is plausible
- Yes for some vaginal infections after a proper history, and sometimes after a test. Many services treat bacterial vaginosis and trichomoniasis by telehealth.
- Abdominal, dental, and C. difficile decisions are usually in-person. Suspected C. difficile needs evaluation, not a leftover Flagyl bottle. Current C. difficile treatment is often a different drug.
What the visit should cover
- Pregnancy trimester, alcohol use, disulfiram, warfarin, and lithium.
- Whether the problem is BV, trichomoniasis, a yeast infection, or a urinary infection. They are treated differently.
- Numbness, seizures, or a need for a long course. Nerve toxicity rises with prolonged use.
- Whether a partner needs treatment and whether you can avoid alcohol for the full window.
When the clinician should refuse
- A sinus infection, a cold, or an uncomplicated UTI.
- Someone who cannot stop alcohol, including hidden alcohol in medicines, for the treatment window.
- Recent disulfiram use.
- Severe abdominal pain, high fever, or diarrhea that might be C. difficile, when the visit cannot examine or test you.
How same-day e-prescriptions and local pickup work. If the drug is prescribed, use a pharmacy you can reach today. Mail order is the wrong speed for an acute infection.
Side effects, allergies, pregnancy, and alcohol
Get care
- Flushing, vomiting, and a pounding heart after alcohol
- Numbness, tingling, or seizure
- Severe diarrhea
- A severe rash or swelling
- Confusion or mood change, especially with disulfiram
Allergies and cross-reaction
A metronidazole allergy is specific. It does not tell you anything about penicillin. Do not substitute tinidazole on your own. That is a related drug with its own alcohol warning.
Pregnancy
Metronidazole is used in pregnancy for some infections, including symptomatic BV and trichomoniasis, when a clinician judges it appropriate. Trimester and dose form matter. Do not start tablets because a friend used the gel.
Alcohol
Avoid alcohol during metronidazole and for at least 3 days after the last dose. The reaction can include flushing, nausea, vomiting, headache, and a fast heart. This includes some sauces, syrups, and mouthwashes. The rule is on the labeling even though a few studies debate how often the reaction occurs.
Severe watery diarrhea during or after any antibiotic can be C. difficile. Mouth or throat swelling is an emergency: call 911 or 999.
Generic, coupon, and telehealth pickup
These are budgeting bands for a common U.S. generic fill, not a national average and not a GoodRx quote. Discount-card prices change by pharmacy and ZIP code, and a card usually cannot be combined with insurance on the same fill. A telehealth visit is a separate bill, often advertised around $29 to $129 in late October 2026. The medicine is extra. Ask the pharmacy for today’s cash price and today’s coupon price before you travel.
| Product | U.S. cash planning band | Discount-card band, GoodRx-type | Telehealth plus local pickup |
|---|---|---|---|
| Generic metronidazole 500 mg, 14 tablets (a common 7-day twice-daily count) | Often about $10–$30 | Often about $5–$20 | Visit fee plus local pickup. Do not use a vaginal gel as if it were those tablets. |
| Brand Flagyl | Usually higher | Generic is the usual fill | Extended-release brand products cost more and follow a different schedule. |
Questions about metronidazole
Can I drink alcohol while taking Flagyl?
No. Avoid alcohol during the course and for at least 3 days after the last dose. The labeling warns of a disulfiram-like reaction. Check cough syrups and mouthwashes.
Can an online doctor prescribe metronidazole?
Often yes for bacterial vaginosis or trichomoniasis when the service can take a proper history and you can avoid alcohol. It should refuse sinusitis, ordinary UTI, and a request to treat undiagnosed severe diarrhea.
Is metronidazole an antibiotic for a UTI or sinus infection?
No. It does not treat routine bladder infections or viral or routine bacterial sinusitis. Using it there adds side effects without treating the cause.
What is the difference between the tablets and the vaginal gel?
The gel stays mostly local and is one BV option. Tablets treat infections that need a body-wide drug, including trichomoniasis. Do not swallow gel, and do not use gel when you were prescribed tablets.
What should I do if I miss a dose?
Take a missed dose when you remember unless it is close to the next dose. Skip it then. Do not take two doses at once. If you vomit soon after a dose, ask the pharmacist before you repeat it. The label and the pharmacist outrank this sentence.
Related pages
- Antibiotic directory and condition matrix
- Telehealth prescription guide
- Safe online pharmacies
- Nitrofurantoin
- Clindamycin
- Amoxicillin
Labels: DailyMed. Stewardship: CDC. Pharmacy checks: FDA BeSafeRx. Codes were read from RxNav on 2 November 2026 for ingredient RxCUI 6922.