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Metronidazole Tablets

Metronidazole Tablets

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  • ✔️ Treats bacterial vaginosis, dental and anaerobic infections effectively
  • ✔️ Targets infection-causing bacteria by disrupting their DNA directly
  • ✔️ Clinically proven antibiotic used across NHS prescribing guidelines
  • ✔️ Suitable for adults treating a wide range of bacterial infections
  • ✔️ Short courses of 5–14 days for fast, targeted infection clearance

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What Are Metronidazole Tablets Used For?

 

Metronidazole tablets are a prescription antibiotic and antiprotozoal medicine used to treat a range of bacterial and parasitic infections. They belong to a class of medicines called nitroimidazoles and have been used in clinical practice for decades. If you have been prescribed this medicine, it is because your doctor or prescriber has identified an infection that responds well to this particular treatment. You can order your prescription conveniently through Cured Pharmacy, a GPhC-registered online pharmacy.

Metronidazole is commonly prescribed for conditions including bacterial vaginosis (BV), dental infections, infected leg ulcers, pressure sores, and certain gastrointestinal infections such as those caused by Helicobacter pylori or Giardia lamblia. It is also used alongside other antibiotics in the treatment of some sexually transmitted infections. If you are managing a related concern, you may also find useful products in our women's health range.

 

How Do Metronidazole Tablets Work?

 

Metronidazole works by targeting the DNA of bacteria and protozoa. Once absorbed into the body, it enters microbial cells and undergoes chemical reduction, producing toxic compounds that damage the organism's DNA. This prevents the bacteria or parasites from replicating and ultimately destroys them. It is particularly effective against anaerobic organisms — those that thrive in low-oxygen environments.

  • Metronidazole is absorbed into bacterial or protozoal cells
  • It is chemically reduced inside the cell to form reactive intermediates
  • These intermediates bind to and disrupt the organism's DNA strands
  • DNA damage prevents replication, killing the microorganism
  • The drug is then metabolised by the liver and excreted via urine

 

Who Should Use Metronidazole Tablets?

 

Metronidazole tablets are suitable for adults and children (depending on the indication and dose) who have been diagnosed with a susceptible infection. They are not suitable for everyone, so a prescriber assessment is always required before dispensing. This medicine is prescription-only in the UK.

  • Adults with bacterial vaginosis or trichomoniasis
  • Patients with dental or oral infections caused by anaerobic bacteria
  • Individuals with H. pylori infection (as part of eradication therapy)
  • People with protozoal infections such as giardiasis or amoebiasis

 

How Do Metronidazole Tablets Compare to Metronidazole Gel?

 

Feature Metronidazole Tablets (Oral) Metronidazole Gel (Topical)
Route of administration Oral (swallowed) Topical (applied locally)
Common uses BV, dental infections, protozoal infections BV (intravaginal), rosacea (facial)
Systemic absorption High — reaches bloodstream Low — mainly local action
Alcohol interaction Yes — must avoid alcohol Lower risk but caution still advised

 

How Should You Store Metronidazole Tablets?

 

Store your metronidazole tablets below 25°C in a dry place, away from direct sunlight. Keep them in their original packaging and out of reach of children. Do not use the tablets after the expiry date printed on the pack. If you have leftover tablets after completing your course, return them to a pharmacy for safe disposal — do not flush them down the toilet or throw them in household waste.

If you are also managing a related condition such as a fungal infection alongside your bacterial infection, take a look at our athletes foot and fungal infections range for additional support products.

This product is a medicine. Speak to your doctor or pharmacist before using if you have an underlying medical condition or are taking other medicines.

Metronidazole Tablets specifications
Treatment category Antibiotic / Antiprotozoal
Mechanism of action DNA disruption in anaerobic bacteria and protozoa
Effective against Anaerobic bacteria, protozoa (e.g. Giardia, Trichomonas)
Suitable for Adults and children (dose-dependent); not suitable in first trimester of pregnancy without specialist advice
Active ingredient Metronidazole
Pack sizes 21 tablets (standard course pack)
Strengths 200mg, 400mg
UK classification Prescription Only Medicine (POM)
Drug class Nitroimidazole
Preparation Film-coated tablet
Route of administration Oral

Specifications of Metronidazole Tablets

 

What Is Metronidazole and What Is It Used For?

 

Metronidazole is an antibiotic and antiprotozoal medicine belonging to the nitroimidazole class. It is used to treat infections caused by anaerobic bacteria and certain parasites. In the UK, it is a prescription-only medicine (POM) and is widely used across NHS and private practice settings.

Conditions commonly treated with metronidazole tablets include bacterial vaginosis, dental abscesses, infected wounds, pelvic inflammatory disease (as part of combination therapy), Helicobacter pylori eradication, giardiasis, and amoebiasis. It may also be used to prevent infection following certain surgical procedures.

 

What Do You Need to Know Before Using Metronidazole Tablets?

 

Before starting metronidazole, it is important to tell your prescriber about any existing health conditions and medicines you are currently taking. This medicine is not suitable for everyone.

Do not take metronidazole if you:

  • Are allergic to metronidazole or any other nitroimidazole antibiotic
  • Are in the first trimester of pregnancy (use only if clearly necessary and under medical supervision)
  • Have a history of blood disorders caused by metronidazole
  • Are taking disulfiram (Antabuse) or have taken it within the last two weeks

Use with caution if you have:

  • Liver disease or hepatic impairment
  • A history of neurological conditions or seizures
  • Severe renal impairment

Known drug interactions — tell your prescriber if you take:

  • Warfarin or other anticoagulants (metronidazole can increase bleeding risk)
  • Lithium (risk of lithium toxicity)
  • Ciclosporin (increased ciclosporin levels)
  • Phenytoin or phenobarbitone (altered drug levels)
  • Fluorouracil (increased toxicity risk)
  • Busulfan (increased busulfan plasma levels)

 

How Should You Use Metronidazole Tablets?

 

Always take metronidazole exactly as your prescriber has directed. Do not stop the course early, even if you feel better — completing the full course helps prevent the infection from returning or becoming resistant to treatment.

  1. Swallow the tablet whole with a full glass of water
  2. Take with or after food to reduce the chance of stomach upset
  3. Space your doses evenly throughout the day
  4. Do not crush or chew the tablets unless advised to do so
  5. Complete the full prescribed course
  6. Avoid alcohol throughout treatment and for at least 48 hours after your last dose
Indication Age Group Dose Frequency
Bacterial vaginosis Adults 400mg Twice daily for 5–7 days
Dental infection Adults 200–400mg Three times daily for 3–7 days
H. pylori eradication Adults 400mg Twice daily (as part of triple therapy)
Giardiasis Adults 2g single dose or 400mg Three times daily for 5 days
Giardiasis Children (1–3 years) 500mg Once daily for 3 days (as directed by prescriber)

Doses listed are for guidance only and reflect standard NHS prescribing ranges. Your prescriber may adjust the dose based on your individual circumstances. If you are also managing a related digestive concern, our IBS and cramps range may offer additional support products.

 

What Are the Possible Side Effects of Metronidazole Tablets?

 

Like all medicines, metronidazole can cause side effects, although not everyone experiences them. Most side effects are mild and resolve once the course is complete.

Common side effects (may affect up to 1 in 10 people):

  • Nausea or feeling sick
  • Metallic or bitter taste in the mouth
  • Loss of appetite
  • Stomach pain or discomfort
  • Headache
  • Dizziness

Less common side effects (may affect up to 1 in 100 people):

  • Vomiting or diarrhoea
  • Furring of the tongue
  • Dark or discoloured urine (harmless)
  • Skin rash or itching
  • Peripheral neuropathy (tingling or numbness in hands or feet) — particularly with prolonged use

Stop taking metronidazole and seek urgent medical advice if you experience signs of a severe allergic reaction (swelling of the face, lips, or throat; difficulty breathing; severe skin rash), seizures, or significant neurological symptoms.

 

How Should You Store Metronidazole Tablets?

 

  • Store below 25°C in a dry place
  • Keep away from direct sunlight and moisture
  • Store in the original packaging
  • Keep out of the sight and reach of children
  • Do not use after the expiry date on the pack
  • Return unused tablets to a pharmacy — do not dispose of in household waste or flush down the toilet

If you are managing a related condition such as a urinary tract or bladder infection alongside your treatment, you may find our cystitis and bladder infection range helpful for supportive products.

Written and reviewed by our qualified team

Your safety and success are our highest priorities. Our medical team rigorously evaluates every product and piece of advice we provide, ensuring you receive only the most effective, science-backed solutions available.

Frequently Asked Questions

Where can I buy metronidazole tablets online in the UK?

You can order metronidazole tablets through Cured Pharmacy, a GPhC-registered UK online pharmacy. Because metronidazole is a prescription-only medicine, you will need to complete a short online consultation before your order is reviewed and dispensed. Once approved, your tablets are dispatched promptly to your door.

How do metronidazole tablets work in the body?

Metronidazole enters bacterial and protozoal cells and is chemically reduced to form reactive compounds that damage the organism's DNA. This prevents the microorganism from reproducing and ultimately destroys it. It is especially effective against anaerobic bacteria — those that survive in low-oxygen environments — and certain parasites.

What infections are metronidazole tablets used to treat?

Metronidazole tablets are used to treat bacterial vaginosis, dental abscesses, infected wounds, pelvic inflammatory disease (in combination), Helicobacter pylori infection, giardiasis, and amoebiasis. They may also be used to prevent infection after certain surgical procedures. Your prescriber will confirm whether metronidazole is appropriate for your specific infection.

What is the correct dose of metronidazole tablets for bacterial vaginosis?

The standard NHS-recommended dose for bacterial vaginosis in adults is 400mg twice daily for 5 to 7 days. Some prescribers may recommend a single 2g dose as an alternative, though the twice-daily course is generally preferred for better tolerability. Always follow the specific instructions given by your prescriber.

Can I drink alcohol while taking metronidazole tablets?

No — you must not drink alcohol during your course of metronidazole and for at least 48 hours after your final dose. Combining alcohol with metronidazole can trigger a disulfiram-like reaction, causing flushing, nausea, vomiting, rapid heartbeat, and severe discomfort. This is one of the most important warnings associated with this medicine.

What are the most common side effects of metronidazole tablets?

The most commonly reported side effects include nausea, a metallic or bitter taste in the mouth, headache, dizziness, and loss of appetite. These effects are usually mild and tend to improve as your body adjusts. Taking the tablets with food can help reduce stomach-related side effects.

What happens if I miss a dose of metronidazole tablets?

If you miss a dose, take it as soon as you remember — unless it is nearly time for your next scheduled dose, in which case skip the missed one and carry on as normal. Never take two doses at the same time to compensate for a missed one. Maintaining a regular dosing schedule helps the medicine work effectively.

How long does a course of metronidazole tablets last?

The duration of treatment depends on the infection being treated. Most courses last between 5 and 14 days, though some single-dose regimens exist for specific conditions. It is essential to complete the full prescribed course even if your symptoms improve early, as stopping too soon can allow the infection to return or become harder to treat.

Is metronidazole safe to take during pregnancy?

Metronidazole should be used with caution during pregnancy, particularly in the first trimester, and only when clearly necessary under medical supervision. It is sometimes prescribed during the second and third trimesters for conditions such as bacterial vaginosis when the benefits outweigh the risks. Always discuss your pregnancy with your prescriber before starting any antibiotic.

Who is not suitable for metronidazole tablets?

Metronidazole is not suitable for people who are allergic to metronidazole or other nitroimidazole antibiotics, those currently taking or who have recently taken disulfiram, or those with a history of blood disorders caused by this medicine. People with severe liver disease or a history of seizures should also use it with caution and only under medical guidance.

What medicines interact with metronidazole tablets?

Metronidazole can interact with several medicines, including warfarin (increasing bleeding risk), lithium (raising toxicity risk), ciclosporin, phenytoin, fluorouracil, and busulfan. Always tell your prescriber and pharmacist about every medicine, supplement, or herbal remedy you are taking before starting metronidazole. If you are managing related conditions, our condoms and sexual health range may also be relevant.

How do I manage side effects of metronidazole tablets?

Taking metronidazole with food or a glass of milk can help reduce nausea and stomach discomfort. Staying well hydrated and avoiding alcohol entirely during treatment also helps minimise side effects. If side effects are severe or persistent — particularly any tingling or numbness in your hands or feet — contact your GP or pharmacist promptly.

What are the alternatives to metronidazole tablets?

Alternatives depend on the infection being treated. For bacterial vaginosis, topical clindamycin cream or metronidazole vaginal gel are options. For dental infections, amoxicillin or co-amoxiclav may be prescribed. For protozoal infections, tinidazole is a related nitroimidazole sometimes used as an alternative. Your prescriber will recommend the most appropriate treatment for your situation.

How long do the effects of metronidazole tablets last after finishing the course?

Metronidazole has a half-life of approximately 8 hours, meaning it is largely cleared from your body within 1 to 2 days of finishing the course. However, the alcohol interaction warning applies for at least 48 hours after your last dose. Symptom improvement should be noticeable within a few days of starting treatment, though the full course must always be completed.

What are the latest clinical findings on metronidazole tablets?

Metronidazole remains a first-line treatment for bacterial vaginosis and anaerobic infections according to current NHS and NICE guidance. Research continues to explore its role in combination therapies for H. pylori eradication and its use in surgical prophylaxis. Antimicrobial resistance to metronidazole in some organisms is an evolving area of study, reinforcing the importance of completing prescribed courses and not using antibiotics unnecessarily. You can find further supportive products in our oral health range if you are being treated for a dental infection.

How Should You Use Metronidazole Tablets?

Always take metronidazole tablets exactly as your prescriber has instructed. Do not adjust your dose or stop the course early without medical advice, even if you start to feel better. Completing the full course is essential to clear the infection properly and reduce the risk of antibiotic resistance.

Follow these steps each time you take your tablets:

What Is the Correct Dose of Metronidazole Tablets?

The correct dose depends on the type and severity of the infection being treated, as well as your age and overall health. Your prescriber will specify the exact dose on your prescription label. The table below reflects standard NHS prescribing guidance for common indications.

When Is the Best Time to Use Metronidazole Tablets?

There is no single "best" time of day to take metronidazole, but consistency matters. Taking your doses at the same times each day — for example, with breakfast, lunch, and dinner for a three-times-daily course — helps maintain steady levels of the medicine in your bloodstream. This consistency is what keeps the antibiotic working effectively throughout the day.

Setting a daily reminder on your phone can be a simple but effective way to stay on track, particularly for longer courses. If you are taking metronidazole twice daily, spacing doses approximately 12 hours apart is ideal.

How Long Can You Use Metronidazole Tablets For?

The length of your course will be determined by your prescriber based on the infection being treated. Most standard courses range from 3 to 14 days. Longer-term use is occasionally required for certain conditions but is generally avoided due to the increased risk of side effects such as peripheral neuropathy with prolonged treatment.

Do not take metronidazole for longer than prescribed, and do not restart a course without consulting your prescriber. If your symptoms have not improved by the end of your course, contact your GP or prescriber for further assessment rather than self-treating.

Do not exceed the recommended dose. If in doubt, speak to your pharmacist.

What Are the Most Common Side Effects of Metronidazole Tablets?

Most people who take metronidazole tolerate it well, but some do experience side effects. The most frequently reported ones tend to be mild and often settle on their own as your body adjusts to the medicine. Taking your tablets with food can help reduce stomach-related symptoms.

  • Nausea or feeling sick
  • Metallic or bitter taste in the mouth
  • Loss of appetite
  • Stomach pain or cramping
  • Headache
  • Dizziness

What Are the Less Common Side Effects of Metronidazole Tablets?

Less common side effects occur in a smaller proportion of people but are still worth being aware of. If any of the following become troublesome or persistent, speak to your pharmacist or GP.

  • Vomiting or diarrhoea
  • Furring or discolouration of the tongue
  • Dark or reddish-brown urine (harmless but can be alarming)
  • Skin rash, itching, or flushing
  • Dry mouth
  • Vaginal irritation or discharge changes (when treating BV)

What Are the Serious Side Effects of Metronidazole Tablets?

Serious side effects are uncommon but require prompt medical attention. Peripheral neuropathy — tingling, numbness, or weakness in the hands or feet — can occur, particularly with prolonged use. This is why metronidazole is generally prescribed for short courses only. Seizures and encephalopathy (confusion, altered consciousness) have been reported rarely, especially in people with pre-existing neurological conditions or liver disease.

Signs of a severe allergic reaction include swelling of the face, lips, tongue, or throat, difficulty breathing, and a widespread skin rash. If you experience any of these, stop taking the medicine immediately and call 999 or go to your nearest A&E.

What Should You Do If You Experience Side Effects of Metronidazole Tablets?

For mild side effects such as nausea or a metallic taste, taking the tablets with food and staying well hydrated usually helps. Avoid alcohol entirely — not only does it interact dangerously with metronidazole, but it can also worsen nausea and dizziness. If side effects are affecting your daily life or do not improve after a few days, contact your pharmacist or GP for advice.

You can also report suspected side effects directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. This helps improve medicine safety monitoring across the UK.

Can Metronidazole Tablets Interact With Other Medicines?

Yes — metronidazole has several clinically significant drug interactions. It can increase the anticoagulant effect of warfarin, raising the risk of bleeding. It may also increase lithium levels in the blood, potentially causing toxicity. Other interactions include ciclosporin, phenytoin, fluorouracil, and busulfan. Always inform your prescriber and pharmacist of every medicine, supplement, or herbal product you are taking before starting metronidazole.

Disulfiram (used to treat alcohol dependence) must not be taken alongside metronidazole or within two weeks of stopping it, as the combination can cause serious psychiatric and neurological reactions.

If you are concerned about any side effects, contact your pharmacist or GP immediately.

Patient Information Leaflet

Important - Before taking any medication, it is always important to read the Patient Information Leaflet (PIL)

Written and reviewed by our qualified team

GPhC Number: 2233073
Tarun Kumar

Reviewed by:

Tarun Kumar

Superintendent/ Clinical Lead

📖 Find out more about our team of medical content authors and how we ensure the accuracy of our content with our content guidelines.

Content last updated: 31 Mar 2025

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