Buy metronidazole 400mg tablets from a registered UK pharmacy

  • Powerful prescription antibiotic used to treat a variety of bacterial infections
  • Used to treat bacterial vaginosis (BV) in women
  • Order online after a quick consultation, for fast and discreet delivery to your door
  • Available from £13.99 + prescription fees and delivery costs

Our prices

Strength Quantity Price Stock
400mg10 tablets£13.99Out of Stock
Prices exclude a prescription fee. This treatment requires a quick online consultation,
which a doctor will review to determine if a prescription is appropriate.

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Dr Samantha Miller

Reviewed by Dr Samantha Miller MB ChB
(2017, University of Glasgow)
GMC number: 7561464

Information last reviewed 10/04/2021


What is metronidazole?

Metronidazole, (often supplied under the brand name Flagyl) is an antibiotic used to treat a wide variety of bacterial and parasitic infections. It is used to treat infection of the skin and mouth, the respiratory system, the gastrointestinal tract and much of the reproductive system. Metronidazole is commonly prescribed to treat bacterial vaginosis (BV) in women.

How does metronidazole work?

Metronidazole works by preventing certain bacteria from reproducing and spreading, giving your body’s immune system the chance to get rid of the infection. For treatment of BV, this allows the natural balance of bacteria in the vagina to be restored.

How long does metronidazole take to work?

Metronidazole should begin to make you feel better within a few days. However, you must finish the full course of tablets even if you are feeling better.

Metronidazole summary


One tablet, three time per day for 5-7 days

Type of Medicine

Nitroimidazole antibiotic


Inhibits nucleic acid synthesis, disrupting DNA synthesis in bacteria, which prevents essential cell functions and replication

Available Size

10 tablets

Available Strengths


Active Ingredient



From £1.40 per tablet

Side Effects

Can include mental confusion, hallucinations, convulsions, headache, skin rash, darkening of the urine, muscle or joint pain


Active ingredients

The active ingredient of each metronidazole tablet is 400 milligrams (mg) metronidazole.

Inactive ingredients

The inactive ingredients are povidone, magnesium stearate, colloidal anhydrous silica and maize starch.

Please note: different brands of generic metronidazole may contain different ingredients than those listed here.

Which ingredients can cause an allergic reaction?

Metronidazole is not known to cause severe allergic reactions in people unless you have a hypersensitivity to this medication. However, as it does contain lactose as one of its inactive ingredients, if you have a severe lactose intolerance you might experience some uncomfortable gastrointestinal symptoms. It is otherwise present in small safe amounts and should not affect you if you have mild lactose intolerance.


How to take metronidazole

Always take metronidazole as instructed by a doctor or pharmacist as the dose may differ depending on what type of infection you have. For treatment of bacterial infections in adults, a typical dose is 400mg three times per day (every 8 hours) for 5–7 days. For treatment of bacterial vaginosis, the dose is usually 400mg twice per day for 5–7 days; or alternatively a single dose of 2g. Your prescriber will inform you of the correct dose and duration of treatment. 

Swallow the tablets whole with a glass of water, preferably during or just after a meal to avoid side effects such as nausea or vomiting. Do not crush or chew the tablets. If you forget to take a dose, try and take it as soon as you remember. However, if it is nearly time for your next dose, just skip the forgotten dose and take the next one as planned. Never take a double dose to make up for a missed one.

Can metronidazole tablets be crushed or split?

Metronidazole tablets should not be crushed or split.

Side Effects

Metronidazole side effects

Like all medications, metronidazole can cause side effects in some patients. If you experience any of the following rare side effects, stop taking Metronidazole and seek medical attention immediately:

  • Symptoms of an allergic reaction: skin rash, sore lips or mouth, wheezing, tightness of the chest, swelling of the face, tongue or throat, difficulty breathing, itchy rash
  • Symptoms of encephalopathy (a brain disease): fever, stiff neck, headache, hallucinations, problems using your arms and legs, problems with speaking or feeling confused
  • Skin rashes with blistering, peeling or bleeding around the lips, eyes, mouth, nose or genitals, flu-like symptoms or a high temperature, all of which could be symptoms of Steven-Johnson syndrome or toxic epidermal necrolysis.
  • A red, scaly, widespread rash with bumps or blisters on the skin, accompanied by fever, which may be acute generalised exanthematous pustulosis.

Speak to your doctor if you experience any of the following side effects:

  • Jaundice (yellowing of the skin or whites of the eyes)
  • Unexpected infections, mouth ulcers, bruising, bleeding gums or severe tiredness, which could indicate blood problems
  • Severe stomach pain which may reach through to your back (pancreatitis)

The following side effects affect less than 1 in 10,000 people, but should be reported immediately to a doctor or pharmacist:

  • Fits (convulsions)
  • Mental confusion or hallucinations
  • Blurred or double vision
  • Skin rash and flushing
  • Headache
  • Darkening of the urine
  • Feeling sleepy or dizzy
  • Muscle or joint pain
  • Hepatocellular liver injury, which may cause jaundice

The frequency of the following side effects cannot be estimated from the available data, these should be reported to your doctor also:

  • Vaginal thrush
  • Numbness, tingling, pain or weakness in the arms or legs
  • Unpleasant taste in the mouth
  • Furred tongue
  • Nausea, vomiting, or diarrhoea
  • Loss of appetite
  • Fever
  • Depression
  • Optic neuritis (pain in the eyes)
  • Fever accompanied by nausea, vomiting, headache, stiff neck and sensitivity to light, which could be caused by meningitis
  • Hearing impairment or loss
  • Tinnitus
  • Skin rash with or without raised areas recurrent in the same skin area each time the drug is taken

How to cope with the side effects of metronidazole

One of the most common side effects is nausea. If you experience this then it’s helpful to have small, simple meals and avoid overly spicy or rich foods. Drink plenty of water, particularly if you have vomiting. If the nausea is troublesome or if vomiting is preventing you from taking the tablets, consult your doctor as there may be a more suitable alternative treatment. 


Do NOT take metronidazole tablets if you are allergic to any of the ingredients in this medication, or to other nitroimidazoles e.g. tinidazole.

Take particular caution and tell your doctor or pharmacist if:

  • You have or have ever had liver problems
  • You have kidney problems and are having dialysis
  • You have a condition called porphyria (a blood disorder leading to abnormal sensitivity to sunlight and other problems)
  • You have an intolerance to lactose or other sugars
  • You are affected by Cockayne syndrome, a rare disease that causes severe sensitivity to sunlight

Drug interactions

Before taking metronidazole, tell your doctor or pharmacist if you are taking any other medications, including those purchased over the counter without a prescription. In particular, tell your doctor or pharmacist if you are taking any of the following:

  • Anticoagulants such as warfarin
  • Medications used to treat epilepsy (e.g. phenobarbital, phenytoin, primidone)
  • Lithium (used to treat mental illness)
  • 5 fluorouracil for cancer
  • Busulfan for leukaemia
  • Ciclosporin
  • Disulfiram (used to treat alcoholism)
  • Medicines used to treat stomach ulcers e.g. cimetidine

Metronidazole and pregnancy

Metronidazole should not be taken during pregnancy or breastfeeding unless absolutely necessary. You should inform your doctor if you are pregnant, think you might be pregnant or plan to become pregnant before taking this medication.

Metronidazole and alcohol

Do not drink alcohol while taking metronidazole or for the 48 hours after finishing your course. Combining alcohol with this medication can cause unpleasant side effects such as nausea, vomiting, stomach pain, hot flushes, heart palpitations and headaches.

Treatment Options

Metronidazole tablets vs gel

For the treatment of infections such as bacterial vaginosis, there is little difference in effectiveness between metronidazole tablets and gel, and both work effectively to eradicate BV. The gel tends to be more expensive than the tablets and carries a slightly higher chance of causing vaginal thrush as a side effect.  The tablets are more likely to induce gastrointestinal side effects such as nausea or vomiting, although these can be avoided by taking each dose with food. Each patient reacts differently to different forms of antibiotic, so if you are worried about any side effects, speak to your doctor for advice. 


When can I stop taking metronidazole?

Metronidazole is an antibiotic, so it is vital that you complete the full course of treatment prescribed to you by your doctor. The length of the course will depend on the type of infection being treated, and even if your symptoms have gone, you must continue until the end of the course.

Does metronidazole affect birth control?

Metronidazole itself does not affect any type of oral contraception or prevent it from working. However, if you experience vomiting or severe diarrhoea as a side effect of metronidazole, your contraceptive pill may not prevent pregnancy. See the packet instructions of your contraception for advice if this happens.

Is metronidazole an antibiotic?

Metronidazole is an antibiotic that is used to treat a wide variety of bacterial and parasitic infections.

Does metronidazole cause thrush?

Metronidazole can cause thrush in some patients if the antibiotics attack the normal, harmless bacteria which live in the vagina. This is more common in patients who use metronidazole gel rather than tablets.

Can metronidazole affect fertility?

Metronidazole does not affect fertility in men or women, but you should seek advice from your doctor if you are trying to get pregnant while using this medication.

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I moved 150 miles from my GP (to uni) and was unable to go home or visit a walk in for another 2 days due to being at work (12.5 hour shifts). I filled out a quick form - and 1.5 days later I had my antibiotics delivered to my door and I am on the mend. 10/10.