The FDA label for metronidazole (Flagyl) says to stop alcohol, and products with propylene glycol, while you take it and for at least three days after. It warns that stomach cramps, nausea, vomiting, headaches, and flushing may occur. The CDC's 2021 STI treatment guidelines disagree. In their section on bacterial vaginosis, they say avoiding alcohol while taking metronidazole is unnecessary. The label is the drug's official directions, so ask your prescriber or pharmacist which advice applies to you. If you already drank, do not stop or skip the antibiotic because of it.
Medical disclaimer: This article is general information about a drug interaction and is not medical advice. Consult your doctor or pharmacist for advice specific to your medications.
What the FDA actually says
The FDA prescribing information for metronidazole (brand name Flagyl) is posted on DailyMed, the National Library of Medicine's drug label site. The label says using oral metronidazole "is associated with a disulfiram-like reaction to alcohol, including abdominal cramps, nausea, vomiting, headaches, and flushing."
The label is specific about timing too. In its advice for patients, it says: "Discontinue consumption of alcoholic beverages or products containing propylene glycol while taking metronidazole and for at least three days afterward because abdominal cramps, nausea, vomiting, headaches, and flushing may occur." So the label's window is the whole course plus at least 3 more days.
What the CDC guidelines say
The CDC reaches a different conclusion. Its 2021 STI Treatment Guidelines cover alcohol in the section on bacterial vaginosis. There, the CDC cites a review that "reported no in vitro studies, animal models, reports of adverse effects, or clinical studies providing convincing evidence of a disulfiram-like interaction between alcohol and metronidazole." The older warning, the guidelines add, came from lab experiments and individual case reports. In those reports, the reactions "were equally likely to have been caused by alcohol alone or by adverse effects of metronidazole." Their conclusion is that avoiding alcohol while taking metronidazole is unnecessary.
The review is a 2014 article by Fjeld and Raknes in a Norwegian medical journal. It is written in Norwegian, with an English summary. The authors searched published studies in PubMed and the World Health Organization's database of side effect reports. The summary concludes: "Recent research does not confirm a clinically relevant interaction between ethanol and metronidazole."
| Source | What it says about alcohol |
|---|---|
| FDA label for metronidazole tablets (on DailyMed) | Stop alcohol and products with propylene glycol during treatment and for at least three days after. Stomach cramps, nausea, vomiting, headaches, and flushing may occur |
| CDC 2021 STI Treatment Guidelines (bacterial vaginosis section) | A review found no convincing evidence of a disulfiram-like interaction, so avoiding alcohol while taking metronidazole is unnecessary |
What this means for you
This page does not pick a side for you. The label is the official set of directions for the drug. Ask the doctor who prescribed it, or your pharmacist, which advice applies to you. And if you already drank, do not stop or skip the antibiotic because of it.
Why the reaction may happen
Normally your body breaks alcohol down in two steps. First alcohol turns into a substance called acetaldehyde. Then an enzyme called acetaldehyde dehydrogenase clears the acetaldehyde away. Disulfiram is a medication used to help some people stop drinking. Its FDA label says it blocks this process at the acetaldehyde stage. Acetaldehyde builds up and causes flushing, a throbbing headache, nausea, and vomiting. The metronidazole label calls its reaction "disulfiram-like" after this drug. If you take disulfiram, or stopped it in the last two weeks, tell your doctor before you start metronidazole. The metronidazole label says it should not be given to people who took disulfiram within the last two weeks, because using the two together has been linked to psychotic reactions.
Does metronidazole block the same enzyme? The CDC guidelines say no: "Metronidazole does not inhibit acetaldehyde dehydrogenase, as occurs with disulfiram." They say alcohol alone, or side effects of metronidazole itself, might explain why people suspected a disulfiram-like reaction.
The hidden sources of alcohol
The trap is that alcohol is not only in drinks. The label also names products with propylene glycol, and some cold medicines and mouthwashes list alcohol as an ingredient.
| Watch out for | Why |
|---|---|
| Beer, wine, spirits, hard seltzer | Obvious alcohol. The label says to stop during and for at least 3 days after |
| Some cough syrups and cold medicines | Can contain alcohol or propylene glycol. The NyQuil Cold & Flu liquid label lists both |
| Mouthwash with alcohol | The Listerine Cool Mint label lists 21.6% alcohol and says do not swallow |
When you pick up the prescription, ask your pharmacist to flag any of your other products that contain alcohol or propylene glycol.
What if you already drank
If you had a drink and then realized, do not panic. Do not stop or skip your antibiotic because of it either. Stop drinking. If symptoms are severe, like chest pain, trouble breathing, vomiting that will not stop, or a racing heart, get medical help. For milder symptoms, call your pharmacist or the doctor who prescribed it. There is one time the label does say to stop: if you get nerve symptoms, such as numbness or tingling in your hands or feet, stop the drug and tell your doctor right away. MedlinePlus also lists problems with coordination and confusion among the symptoms to call your doctor about immediately. The label's instruction is to stop alcohol for the rest of your course and for at least 3 days after.
And do not stop the antibiotic early just to drink sooner. Finishing the full course matters, as covered in our guide on what to do after a missed antibiotic dose. For other drink-and-medication timing, see medication and alcohol. On doxycycline instead? See doxycycline and alcohol.
If you took two metronidazole doses by mistake, see what to do after a double dose of metronidazole.
How Pillo helps you finish the course
The label's 3-days-after window is easy to lose track of, especially once you feel better. Knowing the date of your last dose helps.
With Pillo, you can schedule your metronidazole doses, and the persistent alarm keeps going until you respond. Your dose history shows when you took your last dose, so you can count at least 3 days from there, as the label says. You can download Pillo on Google Play to track your course.
Frequently Asked Questions
Can I drink alcohol while taking metronidazole?
The FDA label says no. It tells patients to stop alcohol and products with propylene glycol during treatment and for at least three days after. Stomach cramps, nausea, vomiting, headaches, and flushing may occur. The CDC's 2021 STI treatment guidelines disagree. In their section on bacterial vaginosis, they say avoiding alcohol while taking metronidazole is unnecessary. Ask your prescriber or pharmacist which applies to you.
How long after metronidazole can I drink alcohol?
At least 3 days after your last dose, according to the label. Its advice for patients is to stop alcohol and products with propylene glycol "while taking metronidazole and for at least three days afterward."
What does the metronidazole and alcohol reaction feel like?
Abdominal cramps, nausea, vomiting, headaches, and flushing are the symptoms the label lists. The CDC guidelines say metronidazole does not block the enzyme that disulfiram blocks. They add that alcohol alone, or side effects of metronidazole itself, might explain the reported reactions.
Does the reaction happen with all alcohol, even a little?
The label's instruction is to stop, not cut back. It covers alcohol and products with propylene glycol, during treatment and for at least three days after. That can include hidden sources like some cough syrups. The review the CDC cites found no convincing evidence of a disulfiram-like interaction. If you are not sure, ask your pharmacist or prescriber.
I accidentally drank on metronidazole. What should I do?
Do not stop or skip your antibiotic because of it. Stop drinking. Get medical care for severe symptoms like chest pain, trouble breathing, or vomiting that will not stop. For milder symptoms, call your pharmacist. The label's instruction is to stop alcohol for the rest of your course and for at least 3 days after.
Medical disclaimer: This information is general and educational. It is not a substitute for professional medical advice and cannot account for your health history. Always consult your doctor or pharmacist about your prescription before drinking alcohol.
