Flagyl 400mg

Flagyl 400mg is Abbott's metronidazole 400 mg tablet, made and sold in India. Metronidazole is a nitroimidazole medicine with antibacterial and antiprotozoal action: it kills anaerobic bacteria (germs that grow without oxygen) and some protozoa, notably Trichomonas vaginalis, Entamoeba histolytica (the cause of amoebiasis) and Giardia lamblia. We sell Flagyl 400 in packs of 100, 200 and 300 tablets, from $0.07 a tablet in the largest pack, before shipping.

Four points before you read further. First, Flagyl is not a worm medicine. Our own catalogue category files it under worm treatments, which is wrong: neither the US nor the UK label lists any worm infection among its uses. Second, the US label opens with a boxed warning: metronidazole "has been shown to be carcinogenic in mice and rats", "Unnecessary use of the drug should be avoided", and its use should be reserved for the conditions the label lists. Third, alcohol: the US label says to stop alcohol and products containing propylene glycol during treatment and for at least three days after it; the UK label says at least 48 hours. Fourth, a usual course is 5 to 30 tablets for most infections, and our smallest pack holds 100. In the US, generic metronidazole 500 mg tablets cost pharmacies about 10 cents each, so US readers with a prescription should compare local generic prices first. This page uses the current US generic metronidazole tablet label (the US Flagyl tablet itself is discontinued), the UK product information for metronidazole 400 mg tablets, the Health Canada and Australian registers and Indian pharmacy listings, all listed at the end. We found no published trial of the Indian Flagyl 400 tablet itself.

Flagyl 400mg at a glance

Price per tablet

Prices below are as of October 2026; the pack selector shows the current price.

All three packs cost less than $149, so each one carries the $25 shipping charge when ordered alone. The larger packs are cheaper per tablet before shipping as well as after it, but the cheapest order you can place with us costs $40 delivered.

How many tablets does a course need? Using the adult doses in the UK label (our arithmetic for the tablet counts):

• Trichomoniasis or bacterial vaginosis: 2 g as a single dose is 5 tablets; 400 mg twice daily for 5 to 7 days is 10 to 14 tablets.
• Giardiasis: 2 g once daily for 3 days, or 400 mg three times daily for 5 days, is 15 tablets.
• Amoebiasis: 15 to 30 tablets for most courses; the largest, 800 mg three times daily for 10 days for symptomless cyst passers, is 60 tablets.
• Established anaerobic infection: 800 mg, then 400 mg every 8 hours for about 7 days, is about 22 tablets.
• Leg ulcers and pressure sores: 400 mg three times daily for 7 days is 21 tablets.

So our smallest pack of 100 tablets is more than any single adult course in the UK label, and the 200 and 300 packs are far more than one person needs for one infection. In India, Flagyl 400 is sold in strips of 15 or 20. If you are treating one infection once, the 100 pack is the only one that makes sense, and most of it will be left over. Please do not keep leftover tablets to treat yourself next time. Vaginal discharge or itching is often thrush, which metronidazole does not treat; diarrhoea has many causes; and the US label's boxed warning says unnecessary use of metronidazole should be avoided. For repeat courses of trichomoniasis treatment, the US label recommends an interval of four to six weeks, with the infection confirmed again by laboratory tests and white cell counts before and after re-treatment.

Compared with US generics and the Flagyl brand

NADAC is the US National Average Drug Acquisition Cost: what US pharmacies pay for a medicine, not the price a patient pays. In the NADAC file effective 21 October 2026, all 26 rows for generic metronidazole 500 mg tablets show $0.10449 per tablet. The US label's one-day trichomoniasis treatment is 2 g, four 500 mg tablets, which costs a US pharmacy about $0.42 (our arithmetic). Our cheapest delivered order is $40. Per tablet before shipping, our 300 pack ($0.07) is cheaper than the US acquisition cost (about $0.10); with shipping it is $0.16 a tablet, and nobody needs 300 tablets for one infection, so for a single course a US prescription filled with local generic tablets will almost always cost less. If you are in the US and have a prescription, compare local generic cash prices first.

Flagyl 400 contains the same amount of metronidazole as the UK Flagyl 400 mg tablet, but we have not found a published study comparing the Indian and UK tablets.

Which strength to choose

US prescriptions are written for 250 mg or 500 mg tablets (for example 750 mg three times daily for amoebic dysentery, or 250 mg three times daily for 7 days for trichomoniasis). Those doses cannot be made from whole 400 mg tablets, so if your prescription was written for US strengths, ask the prescriber for a dose that fits this tablet rather than guessing. Flagyl ER 600mg is an extended release tablet with different dosing and is not covered on this page.

How to take Flagyl 400mg: UK label doses by infection

The UK label gives these doses for adults and children over 10 years. Tablet counts are our arithmetic.

The US label covers fewer uses for metronidazole tablets: trichomoniasis, amoebiasis (acute amoebic dysentery and amoebic liver abscess) and serious anaerobic bacterial infections. It does not list bacterial vaginosis or giardiasis as uses for the tablets. For anaerobic infections the US label says intravenous metronidazole is usually given first; the usual oral dose is 7.5 mg/kg every six hours (about 500 mg for a 70 kg adult), and "A maximum of 4 g should not be exceeded during a 24-hour period."

1. Swallow the tablets whole with water, not chewed, during or after a meal (UK label).
2. Take every dose for the full course, even if you feel better early. The US label says skipping doses or stopping early may make the treatment less effective and make resistant bacteria more likely.
3. No alcohol, and no products containing propylene glycol, during the course and for at least three days afterwards (US label; the UK label says at least 48 hours). Check the labels of mouthwashes, cough syrups and other liquid medicines. Our advice is to follow the longer US interval.
4. For trichomoniasis, sexual partners should be treated at the same time to prevent reinfection (US label; the UK label says the partner should receive a similar course where reinfection is likely). The UK label adds that a gonococcal infection might persist after trichomonas has been cleared, so get tested for other sexually transmitted infections.
5. Metronidazole may darken urine (UK label). The US label says this was reported in about one patient in 100,000 and seems to have no clinical significance.
6. Do not drive or use machines if you feel drowsy, dizzy, confused, have hallucinations, fits or vision problems (UK label).
7. If treatment lasts more than 10 days, the UK label advises regular clinical and laboratory checks, especially white cell counts.

Lower doses and extra care for some groups

• Severe liver impairment: the US label says the dose should be reduced by 50% for severe (Child-Pugh C) impairment; no change is needed for mild to moderate impairment, but these patients should be monitored for side effects. The UK Flagyl and Flamingo labels say that for hepatic encephalopathy (confusion caused by liver failure) the daily dose should be reduced to one third and may be given once daily.
• Kidney failure and dialysis: the US label says patients with end-stage kidney disease build up metronidazole breakdown products and should be monitored for side effects; if a dose cannot be separated from a haemodialysis session, an extra dose after dialysis should be considered. The Flamingo UK label says no dose reduction is needed in kidney failure and the dose should be given again straight after haemodialysis.
• Older adults: the US label recommends monitoring for side effects; the UK label suggests cautious use of high dose regimens.
• Children: the US label says safety and effectiveness in children have not been established, except for amoebiasis. The UK label gives children's doses by age; the 400 mg doses in the table above are for adults and children over 10. A child's dose must come from a doctor.

Side effects

Neither label gives percentages for metronidazole side effects, so we have not charted them. The UK label says serious adverse reactions occur rarely with standard recommended regimens.

The boxed warning and long-term use

The US label's boxed warning reads: "Metronidazole has been shown to be carcinogenic in mice and rats ... Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below." The animal studies found tumours of the liver, lungs, breast and lymphatic tissue in rats and mice, but not in hamsters. The UK label adds that "Epidemiological studies have provided no clear evidence of an increased carcinogenic risk in humans", and that because of inadequate evidence on the mutagenicity risk in humans, use for longer than usually required "should be carefully considered". The US label notes reports of breast and colon cancer in people with Crohn's disease treated with high doses for long periods, says a cause and effect relationship has not been established, and states that Crohn's disease is not an approved use. Long courses also carry the nerve damage risk below: the US label says persistent peripheral neuropathy has been reported with prolonged use.

When to get urgent help

Stop taking Flagyl and get medical help straight away if you have:

• Swelling of the face, lips, tongue or throat, trouble breathing or swallowing, or hives. Call emergency services (911 in the US and Canada, 999 in the UK, 000 in Australia).
• Any rash, blisters, peeling skin or a rash with fever. The US label tells patients to stop metronidazole immediately if they develop any type of rash and to seek medical attention, because severe skin reactions can be fatal.
• Numbness, tingling or pain in the hands or feet. The US label says to stop and report any nerve symptoms to your doctor immediately.
• A fit (seizure), confusion, unsteady walking, slurred speech, or a stiff neck with fever and headache. These can be signs of encephalopathy or aseptic meningitis, which the US label says are generally reversible after stopping.
• Any change in your vision or hearing.
• Yellow skin or eyes, dark urine with pale stools, or severe pain in the upper abdomen, which can mean liver injury or pancreatitis. People with Cockayne syndrome should stop at once and report any sign of liver injury (UK label).
• A fast, pounding or irregular heartbeat, or fainting, especially if you take other medicines that affect heart rhythm.
• Severe vomiting, flushing or a pounding headache after alcohol, or diarrhoea that is severe, bloody or does not settle (our advice).

Single doses of up to 15 g (US label) and 12 g (UK label) have been reported in overdoses, with nausea, vomiting and unsteadiness. There is no specific antidote. If someone has taken more than the prescribed dose, contact a doctor or poison centre, and tell emergency staff that the medicine was metronidazole, how much was taken and when.

Who should not take Flagyl 400mg

Never take it if (US label contraindications unless stated):

• you have ever had an allergic reaction to metronidazole or another nitroimidazole medicine, such as tinidazole. The UK label also contraindicates it if you are allergic to any ingredient of the tablet.
• you have taken disulfiram (Antabuse) in the last two weeks: psychotic reactions have been reported with the combination.
• you cannot avoid alcohol or products containing propylene glycol during the course and for at least three days afterwards: the reaction includes abdominal cramps, nausea, vomiting, headaches and flushing.
• you have Cockayne syndrome, a rare inherited disorder: severe irreversible liver damage and fatal liver failure have been reported, with signs of liver failure as soon as 2 days after starting. The UK label puts this as a warning rather than a contraindication: metronidazole should not be used unless the benefit outweighs the risk and no alternative is available, with liver tests before, during and after treatment.
• you are in the first three months of pregnancy and it is for trichomoniasis.

Talk to a doctor first if:

• you are pregnant: the UK label says metronidazole should not be given during pregnancy unless the physician considers it essential, and that the short, high dose regimens are then not recommended. The US label says the one-day 2 g course should not be used for pregnant patients with trichomoniasis. The US label also summarises published studies that include more than 5,000 pregnant women; most of the studies it describes did not show an increased risk of birth defects or other harm to the baby.
• you are breastfeeding: the US label says metronidazole reaches breast milk at levels similar to the mother's blood, and a nursing mother may choose to pump and discard milk during treatment and for 48 hours after the last dose. The UK label says it should not be given during lactation unless the physician considers it essential.
• you have a blood disorder or a history of one (US label: use with caution; white cell counts before and after treatment).
• you have an active or chronic severe disease of the brain, spinal cord or nerves (UK label: use with caution because of the risk of making it worse).
• you have liver disease, kidney failure or are on dialysis (see the dose section above).
• you take medicines that prolong the QT interval (US and UK labels: QT prolongation has been reported, particularly with these), or you have had a long QT interval (our advice).

Medicines that interact with metronidazole

• Alcohol and propylene glycol: see above.
• Disulfiram: not within two weeks (US label).
• Warfarin and other coumarin blood thinners: the effect can increase; prothrombin time and INR should be carefully monitored (US label), and the blood thinner dose may need reducing (UK label).
• Lithium: lithium levels can rise. The US label says serum lithium and creatinine should be checked several days after starting metronidazole; the UK label says lithium treatment should be tapered or withdrawn before metronidazole is given.
• Busulfan: metronidazole can raise busulfan levels; the US label says it "should not be administered concomitantly with busulfan unless the benefit outweighs the risk".
• Medicines that prolong the QT interval: QT prolongation has been reported, particularly with these (US and UK labels).
• Phenytoin and phenobarbital: speed up the breakdown of metronidazole (UK label: half-life cut to about 3 hours); the US label adds that phenytoin clearance can be impaired.
• Cimetidine: may prolong metronidazole's half-life (US label).
• Fluorouracil (5-FU) and ciclosporin: metronidazole can raise their levels; ciclosporin and creatinine should be closely monitored (UK label).
• Blood tests: metronidazole can interfere with some tests for liver enzymes (AST, ALT), LDH, triglycerides and glucose, giving falsely low or zero results. Tell the laboratory you are taking it.

Tell your doctor or pharmacist about every medicine and supplement you take before you start.

Prescription and legal status

Metronidazole tablets are prescription medicines in all four countries we ship to:

• US: generic metronidazole tablets are labelled "Rx only". The Flagyl 250 mg and 500 mg tablets (NDA 012623) are discontinued; Flagyl 375 mg capsules are still listed as a prescription product. The FDA says personal importation of unapproved medicines is illegal in most circumstances, and this Indian pack is not registered with the FDA.
• UK: metronidazole 400 mg tablets are a prescription only medicine (emc), and Flagyl 400 mg tablets are licensed to Sanofi (PL 04425/0746).
• Canada: Health Canada's database lists metronidazole 250 mg tablets and 500 mg capsules as prescription products; we found no 400 mg tablet, and the Sanofi Flagyl capsule entry is cancelled.
• Australia: healthdirect lists Flagyl 400 mg tablets as Schedule 4 (Prescription Only Medicine), available on the PBS.
• India: Apollo Pharmacy marks Flagyl 400 as a prescription medicine and MediBuddy marks it Rx; we did not verify its Indian schedule.

Antibiotics should be taken only for an infection a clinician has diagnosed, at the dose and for the length of time prescribed. Check the rules where you live.

Buying genuine Flagyl

The MHRA warns: "Any medicine not authorised for sale in the UK can be unsafe or ineffective and there is no way of knowing what is in them or the negative health effects they can have." That warning covers this Indian Flagyl pack, which is not the pack authorised in the UK. The MHRA advises UK buyers to "Only use UK-registered pharmacies, including online pharmacies displaying the official green cross logo". When your order arrives, read the strip: it should name Abbott and metronidazole 400 mg, with a batch number and an expiry date. These checks cannot prove that tablets are genuine, because counterfeiters copy packaging. If your symptoms have not improved by the end of the course, see a doctor rather than taking more tablets. If a batch causes unusual symptoms, seek medical advice and report it to your medicines regulator (the MHRA Yellow Card scheme in the UK, FDA MedWatch in the US, the TGA in Australia or Health Canada) as well as to us.

Delivery

We ship Flagyl 400mg to the US, UK, Australia and Canada in plain packaging with tracking. Standard delivery takes 7 to 14 business days to most countries. Shipping costs a flat $25 on orders under $149 and is free from $149. Store the tablets at room temperature, away from light and moisture (Apollo and PharmEasy listings). An infection that needs metronidazole now cannot wait two weeks for tablets to arrive, and bloody diarrhoea, fever, pelvic pain or a dental abscess with swelling needs a doctor or dentist locally. See our shipping page and refund policy.

Related guides

• Flagyl metronidazole: uses, dosage and side effects
• Antibiotic resistance: when antibiotics do not work and what you can do

Other strength: Flagyl 200mg. Related medicines with their own prescriptions and warnings: Tiniba 500mg (tinidazole, another nitroimidazole) and Amicline 500mg (diloxanide furoate, which some doctors give after metronidazole to clear amoebic cysts from the bowel; our note).

Sources

• Metronidazole tablets USP 250 mg and 500 mg, US prescribing information, Teva Pharmaceuticals USA, Rev. J 7/2024, DailyMed setid 291a45f6-ed27-4dcc-8364-358d08623797, version 19: boxed warning, indications, contraindications, warnings, precautions (drug interactions, pregnancy, nursing mothers, pediatric and geriatric use), adverse reactions, overdosage, dosage and administration. DailyMed
• Flagyl 375 capsules, US prescribing information, Pfizer, revised 07/2025, DailyMed setid a2883ca1-5a9a-4259-9d80-46ab67274384. DailyMed
• US Food and Drug Administration, openFDA Drugs@FDA: Flagyl tablets NDA 012623 (discontinued; Federal Register determination that the product was not withdrawn for safety or effectiveness reasons), searched 21 October 2026.
• Metronidazole Tablets BP 400mg, UK Summary of Product Characteristics, Milpharm Ltd (Aurobindo), PL 16363/0026, revised 17 April 2025: sections 4.1 to 4.9, 5.2, 5.3, 6.4. emc
• Metronidazole 400 mg Film-coated Tablets, UK Summary of Product Characteristics, Flamingo Pharma UK Ltd, revised 4 May 2023: sections 4.2 (amoebic liver abscess dose) and 4.4 (kidney failure, dialysis, hepatic encephalopathy). emc
• Flagyl 400 mg Tablets, UK Summary of Product Characteristics, Aventis Pharma Ltd (Sanofi), PL 04425/0746, revised 5 September 2023. emc
• Health Canada Drug Product Database, metronidazole oral products and status, searched 21 October 2026. Health Canada
• healthdirect Australia, Flagyl brand page (400 mg tablets, Schedule 4, PBS), checked 21 October 2026; TGA ARTG 160174, Flagyl metronidazole 400 mg tablet blister pack. healthdirect
• Medicaid NADAC (National Average Drug Acquisition Cost) 2026 dataset, metronidazole 500 mg and 250 mg tablets, per NDC, effective 21 October 2026. data.medicaid.gov
• Apollo Pharmacy listing, Flagyl 400 Tablet 15's, Abbott India Ltd, checked 21 October 2026. Apollo
• PharmEasy listing, Flagyl 400mg Tablet, strip of 15, Abbott Healthcare Pvt Ltd, checked 21 October 2026. PharmEasy
• MediBuddy listing, Flagyl 400 Tablet, strip of 20, Abbott, checked 21 October 2026. MediBuddy
• MHRA. 20 million illegal erectile dysfunction pills seized as MHRA warns against risky online buys, 13 February 2026. GOV.UK
• US Food and Drug Administration. Personal Importation. FDA

This page is for information and is not medical advice. Metronidazole is a prescription medicine in the US, UK, Canada and Australia. Take it only for an infection a clinician has diagnosed, and do not start, stop or change a course without a clinician's advice.