How to Take Metronidazole: Dosage & Safety Guide

In One Sentence: Metronidazole is a prescription antibiotic that must be taken with or after food, swallowed whole with a drink of water, and strictly without any alcohol.

You must take metronidazole tablets with or after a meal, swallowing them whole with a full glass of water. If you have been prescribed this antibiotic for conditions like bacterial vaginosis (BV), dental abscesses, or trichomoniasis, knowing exactly how to take your medication is vital. Taking it incorrectly on an empty stomach can cause severe nausea and stomach upset. In this guide, you will learn the exact steps for taking your tablets, the typical dosages for various infections, and the critical importance of the strict 48-hour alcohol warning. We will also cover what to do if you miss a dose and explain harmless side effects like experiencing a metallic taste.

Key Takeaways

Do you take metronidazole with food?

Yes. Always take your tablets with or immediately after a meal or a snack. Taking metronidazole on an empty stomach drastically increases the likelihood of nausea, vomiting, and general digestive discomfort.

Can you drink alcohol while taking metronidazole?

No, you must avoid all alcohol. Drinking alcohol while taking this antibiotic causes a severe physical reaction. You must wait a full 48 hours after your final dose before drinking any alcohol.

How should I space out metronidazole doses?

You should space your doses evenly throughout the day to keep a constant level of medicine in your body. If taking it twice daily, leave 12 hours between doses. If taking it three times a day, leave 8 hours between doses.

What happens if you miss a dose of metronidazole?

If you forget a tablet, take it as soon as you remember unless it is nearly time for your next scheduled dose. If it is, skip the missed dose completely. Never take a double dose to make up for a forgotten one.

What is Metronidazole?

Metronidazole is a powerful antibiotic designed to treat infections caused by anaerobic bacteria and protozoa (microscopic parasites). In the UK, it is a Prescription-Only Medicine (POM), meaning a qualified healthcare professional must assess you before prescribing it.[1] It is commonly used for infections in the gastrointestinal tract and reproductive system, including bacterial vaginosis (BV) and Trichomoniasis.

The medication comes in two main forms. Immediate-release tablets are absorbed into the body straight away, while extended-release tablets release the medication slowly over time. Both forms are available as cost-effective generic drugs or under brand names like Flagyl. Your doctor will choose the right version based on your specific infection.

How to Take Metronidazole Tablets

To ensure the medication works correctly and to minimise side effects, you must follow specific steps when taking your tablets. Always read the instructions printed on your pharmacy label.

• 1. Take with or after food: Always consume your tablets during a meal or immediately after eating a snack.[2] This coats your stomach and prevents the medication from causing severe nausea.

• 2. Swallow the tablet whole: Take the tablet with a full glass of water. Do not crush, break, or chew the tablet. Metronidazole has an intensely bitter taste that is very unpleasant.

• 3. Space your doses evenly: Setting an alarm on your phone can help you remember to take your doses at equally spaced intervals. This ensures the antibiotic levels remain consistent in your bloodstream.

Understanding Your Dosage

Your correct dosage, drug form, and frequency will depend on your age, the condition being treated, the severity of the infection, and any other medical conditions you have. Your reaction to the initial dose may also affect your treatment plan. Always follow your doctor's guidance on how much to take.

For children aged 0 to 17 with amoebic infections, the usual dose is calculated by body weight (35 to 50 mg/kg daily) and given in three divided doses for 10 days.

Note for Older Adults (65+): As we age, our kidneys may not work as efficiently. This can cause the body to process metronidazole more slowly, resulting in more of the drug staying in the body for a longer time. This increases the risk of side effects. To keep the levels of metronidazole from building up too much, your doctor may start you on a lower dose or a modified medication schedule.

The Golden Rule: Metronidazole and Alcohol

The most important safety rule when taking this antibiotic is the strict avoidance of alcohol. Drinking alcohol while taking metronidazole triggers a severe interaction known as a disulfiram-like reaction.[4] This causes intense nausea, vomiting, stomach cramps, hot flushes, headaches, and a rapid heartbeat.

Crucially, you must continue to avoid all alcohol for exactly 48 hours after you have finished your entire course of antibiotics. It takes this long for your body to completely clear the medication from your system. This warning includes checking the labels of everyday items like mouthwashes and cough syrups, as many contain hidden alcohol.

Missed Doses and Overdoses

If you forget to take a dose, you should take it as soon as you remember. However, if it is nearly time for your next scheduled tablet, simply skip the missed dose and carry on with your normal routine. You must never take a double dose to make up for a forgotten one, as this increases the risk of adverse effects. If you accidentally take too much metronidazole, contact NHS 111 or your doctor immediately for advice.

Common Side Effects and Drug Interactions

Like all antibiotics, metronidazole can cause side effects. Being aware of them can help you feel more prepared and less anxious during your treatment. Up to 1 in 10 people in the UK will experience a sharp, metallic taste in their mouth.[5] This is a completely harmless, temporary side effect that will vanish once you finish the course.

You may also notice that your urine turns a darker, reddish-brown colour. While this can look alarming, it is simply the body safely excreting the medication and is no cause for concern.

Drug Interactions

It is perfectly safe to take everyday, over-the-counter painkillers such as paracetamol or ibuprofen alongside your metronidazole. However, you should always inform your prescriber if you are taking blood thinners (like warfarin) or medications for epilepsy, as metronidazole can alter how these drugs work in your bloodstream.

Medical Disclaimer: The information provided in this article is for educational purposes only and does not replace professional medical advice. It is vital that you complete your entire course of antibiotics, even if you feel better after a few days, to prevent antimicrobial resistance. If you experience severe side effects, such as numbness, tingling, or neurological symptoms, stop taking the medication and contact NHS 111 or your GP immediately. If you require treatment for a condition like Bacterial Vaginosis, you can complete a confidential online consultation with the UK Meds clinical team.

Frequently Asked Questions

Can I take paracetamol with metronidazole?

Yes, it is completely safe to take paracetamol or ibuprofen while you are taking metronidazole. These everyday painkillers do not interact with the antibiotic and can help manage pain or fever associated with your infection.

Why does metronidazole give me a metallic taste?

The metallic taste is a very common, harmless side effect caused by the way the medication interacts with the taste receptors on your tongue as it circulates in your bloodstream. It will disappear completely a few days after you finish your prescription.

How long after metronidazole can I drink alcohol?

You must wait a full 48 hours after taking your final metronidazole tablet before consuming any alcohol. Drinking before this 48-hour window has passed can trigger severe vomiting, stomach pain, hot flushes, and an irregular heartbeat.

Do you have to finish the whole packet of metronidazole?

Yes. You must finish the entire course of antibiotics prescribed to you, even if your symptoms clear up after a few days. Stopping early allows surviving bacteria to multiply and develop resistance to the medication, making future infections much harder to treat.

Does metronidazole affect the contraceptive pill?

Metronidazole does not directly stop the combined contraceptive pill or the mini-pill from working. However, if the antibiotic causes you to experience severe vomiting or diarrhoea, your pill may not be fully absorbed. If this happens, you will need to use extra precautions like condoms.

Final Thoughts From Our Clinical Team

"Metronidazole is an incredibly reliable and effective treatment for a variety of uncomfortable bacterial and parasitic infections. While the instructions may seem strict, particularly the absolute ban on alcohol, following them is the key to a fast, complication-free recovery. We always advise our patients to set reminders on their phones to keep their doses evenly spaced and to make sure they have a small snack handy before taking their tablet. Remember, finishing the entire course is essential for protecting your long-term health and preventing antibiotic resistance."

Sources and References

[1] BNF NICE - Metronidazole. https://bnf.nice.org.uk/drugs/metronidazole/ [Type: Regulatory document]. Accessed: 11 May 2026.

[2] NHS - How and when to take metronidazole [2025]. https://www.nhs.uk/medicines/metronidazole/how-and-when-to-take-metronidazole/ [Type: NHS guidance]. Accessed: 11 May 2026.

[3] National Institute for Health and Care Excellence (NICE) - Clinical Knowledge Summaries: Bacterial vaginosis dosage. [2023]. https://cks.nice.org.uk/topics/bacterial-vaginosis/prescribing-information/oral-metronidazole/  [Type: NICE guideline]. Accessed: 11 May 2026.

[4] National Institute for Health and Care Excellence (NICE) - BNF: Metronidazole interactions. [2026]. https://bnf.nice.org.uk/interactions/metronidazole/ [Type: NICE guideline]. Accessed: 11 May 2026.

[5] National Health Service (NHS) - Side effects of metronidazole. [2025]. https://www.nhs.uk/medicines/metronidazole/side-effects-of-metronidazole/ [Type: NHS guidance]. Accessed: 11 May 2026.

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