Take metronidazole 500 mg exactly as your doctor or pharmacist instructs

Metronidazole 500 mg tablets work best when you take them at the same times each day, with or without food. The standard dose for most bacterial and parasitic infections is one 500 mg tablet three times daily for 7 to 10 days, though your prescription may differ depending on what you are treating. Swallow the tablet whole with a glass of water — do not crush, chew, or split it unless your pharmacist tells you to.

Your pharmacist's label on the bottle will show your specific dose and how many times per day to take it. If the label says something different from what you expect, call the pharmacy before you take the first dose. Metronidazole only works if you finish the entire course, even if you feel better after a few days.

Key Takeaways

  • Take metronidazole 500 mg tablets at the same times each day, following the dose written on your pharmacy label.
  • Swallow tablets whole with water; do not crush or chew them unless your pharmacist says otherwise.
  • Finish all tablets in your course even if symptoms improve, because stopping early can allow infection to return.
  • Avoid alcohol completely while taking metronidazole and for at least 48 hours after your last dose, as it causes severe nausea and vomiting.
  • Tell your doctor about all other medicines you take, because metronidazole interacts with blood thinners, certain seizure drugs, and other medications.

Timing and daily routine

Pick three times of day that are straightforward to remember — for example, breakfast, lunch, and dinner — and take your tablet at those times every day. If you forget a dose, take it as soon as you remember, unless it is almost time for your next dose. In that case, skip the missed dose and continue with your regular schedule. Never take two tablets at once to make up for a missed dose.

If you take metronidazole with food, it may reduce stomach upset, though the tablet works the same way either way. Some people find it easier to take with a meal so they do not forget. Keep the bottle in a place where you see it at those times — next to your toothbrush, on the kitchen counter, or in your bag if you take a dose away from home.

Food, drink, and alcohol interactions

You must avoid all alcohol — including beer, wine, spirits, and products containing alcohol like some cough syrups — while taking metronidazole and for at least 48 hours after your last tablet. Mixing metronidazole with alcohol causes severe nausea, vomiting, flushing, and headache. This reaction can happen even with small amounts of alcohol, so check the labels of any over-the-counter medicines you use.

Food does not prevent metronidazole from working, so you can eat normally. If the tablet upsets your stomach, taking it with food or milk may help. Avoid very spicy foods if they usually trigger stomach problems for you, but there are no specific foods you must avoid while on this medicine.

What to do if you miss a dose or take too much

If you forget a dose, take it as soon as you remember unless your next dose is due within a few hours. Do not double up on tablets to catch up. If you accidentally take more than one tablet at a time, contact your pharmacist or poison control right away — overdose can cause numbness, tingling, or seizures, though this is rare.

If you vomit within an hour of taking a tablet, you may not have absorbed the full dose. Call your pharmacist to ask whether you should take another tablet or wait until your next scheduled dose. Keep the metronidazole bottle and any remaining tablets with you if you go to an emergency room, so doctors know exactly what and how much you took.

Side effects and when to contact your doctor

Common side effects include a metallic taste in your mouth, nausea, headache, and dark or reddish urine — all of these are normal and usually fade as your body adjusts. Take the tablet with food if nausea bothers you. The metallic taste typically goes away after you finish the course.

Contact your doctor if you develop severe diarrhea, numbness or tingling in your hands or feet, confusion, or signs of an allergic reaction such as rash, swelling of the face or throat, or difficulty breathing. These are uncommon but need medical attention. If you have liver disease, kidney problems, or a history of seizures, tell your doctor before starting metronidazole, because the dose may need to be adjusted.

Storage and handling

Store metronidazole tablets at room temperature, away from moisture and heat — a kitchen cabinet or bedroom drawer works well. Keep the bottle tightly closed and out of reach of children and pets. Do not store tablets in the bathroom, where humidity can damage them. Check the expiration date on the label and do not use tablets after that date.

If you have leftover tablets after finishing your course, ask your pharmacist how to dispose of them safely. Do not flush them down the toilet or throw them in the trash unless the label specifically says you can. Many pharmacies have a take-back program for unused medicines.

Medicines and supplements that interact with metronidazole

Tell your doctor or pharmacist about all medicines you take before starting metronidazole, including over-the-counter drugs and supplements. Metronidazole can increase the effect of blood thinners like warfarin, raising your bleeding risk. It also interacts with certain seizure medicines, lithium, and some diabetes drugs.

If you take birth control pills, metronidazole does not reduce their effectiveness, so you do not need backup contraception. However, if you develop diarrhea while on metronidazole, diarrhea itself can reduce how well birth control works, so use a backup method if that happens. Ask your pharmacist to check your full medicine list — they can spot interactions you might miss.

Frequently Asked Questions

Can I take metronidazole on an empty stomach?

Yes, metronidazole works the same way whether you take it with food or without. If it upsets your stomach, taking it with a meal or snack can help reduce nausea. There is no medical reason to avoid taking it on an empty stomach if that works better for your schedule.

What if I cannot swallow the tablet whole?

Ask your pharmacist before crushing or breaking the tablet. Some formulations are designed to be swallowed whole, and breaking them can change how your body absorbs the medicine. Your pharmacist may be able to order a liquid version or a different formulation that you can take instead.

How long does metronidazole take to work?

You may start feeling better within 2 to 3 days, but you must take all tablets for the full course your doctor prescribed — usually 7 to 10 days. Stopping early because you feel better can allow the infection to return or become harder to treat. Finish every tablet even if symptoms disappear.

Can I drink alcohol the day after my last dose?

Wait at least 48 hours after your last metronidazole tablet before drinking any alcohol. Some people experience the reaction even longer after stopping, so if you are unsure, wait a full three days. If you do drink too soon and feel sick, the reaction is uncomfortable but not dangerous — drink water and rest until it passes.

What should I do if I develop a rash while taking metronidazole?

A mild rash may be a normal side effect, but contact your doctor to describe it — where it is, whether it itches, and whether it is spreading. If the rash is severe, covers a large area, or comes with fever or swelling, stop taking the tablets and call your doctor right away, as this could signal an allergic reaction.