Flagyl, otherwise known as metronidazole or Protostat, is a form of antibiotic used for the treatment of various infections. This broad spectrum antibiotic can treat infections caused by both bacteria and parasites. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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Flagyl is a branded version of the medication metronidazole. This is an antibiotic medication used for the treatment of various infections. Flagyl can treat various infections caused by parasites or bacteria.  

What is Flagyl? 

Flagyl, otherwise known as metronidazole or Protostat, is a form of antibiotic used for the treatment of various infections. This broad spectrum antibiotic can treat infections caused by both bacteria and parasites.  

Flagyl is available in a variety of different forms, including an oral capsule, tablet, and a topical cream, gel, or lotion which can be applied directly to the skin. The tablet versions of Flagyl are prescription drugs that should not be taken without doctor approval.  

Immediate release medications release medicine into the body immediately, while extended-release drugs are released over time. Both the immediate and extended-release options for Flagyl are available as a generic drug.  

When is Flagyl used? 

Flagyl is used for the treatment and prevention of various infections. Flagyl can be used for both bacterial and parasitic infections that occur within the bones, abdomen, nervous system, joints, bones, skin and respiratory tract. In some cases, Flagyl can also be used for intestinal and vaginal infections.  

Flagyl is sometimes available in an injectable form that should only be administered by a healthcare provider. Flagyl works by stopping the growth of certain parasites and bacteria. The substance only treats parasitic and bacterial infections and cannot treat viral infections like the common cold.  

Using an antibiotic for treatment when it is not clearly needed could prevent the same medication from working in the future. Flagyl is rarely used alongside other medications for the treatment of stomach or intestinal ulcers caused by the growth of a particular bacteria.  

How do you use Flagyl? 

You should always read the patient leaflet included with a medication before taking it. Flagyl should be taken by mouth when given in tablet form by your doctor or medical consultant. Make sure that you check to ensure that you know when and how to take your medication.  

When taken for the treatment of an infection in tablet form, Flagyl is usually taken by mouth with a full glass of milk or water. You can take this tablet with food to reduce the risk of you feeling nauseas or uncomfortable after taking it.  

Flagyl works best when you maintain a consistent level of the drug in your blood. Because of this, it is important to take Flagyl at regular intervals. If you miss a dose, then you can take it when you remember, as long as another dose is not too close.  

Make sure that you take Flagyl until the full dose is complete. Even if you start to feel better after a couple of days of using this medication, it is important to complete your course. Stopping an antibiotic too early can increase your chances of the infection coming back or you becoming resistant to a drug.  

What dosages are there? 

The typical dose of Flagyl will change according to the kind of medication that you are taking, and the strength. Your doctor or consultant will prescribe your dose according to your situation, previous responses to treatment, and other crucial information.  

For the treatment of a current infection, the usual dose of Flagyl is 1 tablet taken three times a day. This tablet usually contains 500mg of the active ingredient in Flagyl. You should not use Flagyl for 10 consecutive days or longer without the approval of a doctor or medical professional. Overuse of this medication can lead to an increased risk of side effects.  

If you are using Flagyl to prevent an infection, then it may be taken at a lower dose only once per day. Follow the instructions given by your doctor carefully in this case. If you are concerned that you have taken too much Flagyl at once, then speak to a doctor or emergency health provider immediately.  

What are the side effects of Flagyl? 

All medications can sometimes cause side effects as well as the effects that are intended. Usually, Flagyl is well tolerated by a lot of people, and can be an effective treatment. However, it is important to be aware of the possible side effects, just in case you do encounter them.  

The most common side effects of Flagyl are stomach upset, dizziness, headache, vomiting, diarrhea and loss of appetite. You may also notice vomiting and a metallic taste in your mouth. Constipation can be a problem for some people. If any of these symptoms persist or worsen, speak to a doctor.  

Flagyl can cause your urine to turn darker in color. Though this effect is harmless, it may be strange at first. You should find that this problem stops when you finish your medication.  

Remember that this medication was prescribed to you because the benefits were deemed greater than the potential risks. Tell your doctor if you see any more serious side effects such as signs of a new infection, which include a sore throat or easy bleeding and bruising. Abdominal pain, fever, and painful urination can also be signs of an infection.  

You should also seek medical attention immediately if you notice any other serious side effects that can be caused by Flagyl, including: 

  • Dizziness; 
  • Confusion; 
  • Unsteadiness; 
  • Seizure; 
  • Eye pain; 
  • Sudden changes in your vision; 
  • Problems with your speech; 
  • Tingling or numbness in the legs or eyes; 
  • Headache that doesn’t go away; 
  • Painful or stiff neck. 

Using Flagyl for an extended period of time could increase your chances in a new instance of yeast infection or thrush. If you notice a new vaginal discharge or white patches in your mouth, speak to a doctor immediately.  

A very significant allergic reaction to this drug is rare. However, you should always seek medical attention immediately if you notice the symptoms of an allergic reaction, including a rash, swelling in the lips or tongue, or trouble with your dizziness or breathing.  

This is not a complete list of the possible side effects that you may experience when taking Flagyl. If you notice side effects other than the ones mentioned above, speak to a doctor.  

When shouldn’t you use Flagyl? 

Before you begin taking Flagyl make sure that you tell your doctor or consultant if you are allergic to this medication or if you have any other allergies to antibiotics and similar drugs. If you have other allergies that aren’t related to the medication, it is important that your doctor or consultant knows about them. Flagyl can include ingredients that are inactive but may still cause allergic reactions.  

Before taking Flagyl¸ answer any questions that your doctor or consultant has about your medical history. Make sure that you share any background on blood disorders, kidney disease, or liver disease. People with a rare genetic disorder called Cockayne syndrome may be at higher risk of experiencing liver disease when using Flagyl. 

If you have this condition, then you will need to discuss the risks and benefits of this medication with your doctor or consultant. If you need to take this medication anyway, then you may need to have your liver functioning checked regularly. It is also important to watch out for any signs of liver disease during treatment, including loss of appetite, nausea or vomiting, and severe abdominal pain.  

Avoid any alcoholic beverages or products that contain glycol when taking this medication because it could increase your risk of significant side effects, including dizziness, vomiting, headaches and nausea or stomach cramps.  

In certain circumstances, Flagyl and similar medications could cause live bacterial vaccines to be less effective. You should not have any live vaccinations or immunizations with this medication unless you are told otherwise by a doctor.  

Before you have any surgery with Flagyl, tell your doctor or dentist about all products that you use, and make sure that your doctor is aware of your background. If you are pregnant or breastfeeding, make sure that you speak to your doctor about the positives and negatives of taking Flagyl.  

Does Flagyl interact with other medications? 

Flagyl could potentially interact with other medications which could increase your risk of dangerous side effects. It is important to keep a complete list of all the medications that you use so that you can share them with your doctor if you need to take a new drug. You should tell your doctor about all over the counter and herbal remedies you use, as well as prescription medications.  

Alcohol containing products can interact negatively with this medication and increase your chances of side effects. Additionally, products containing lithium or glycol could also lead to negative side effects. You should not take Flagyl if you are taking disulfiram within the last 2 weeks.  

Flagyl could interfere with tests and cause positive or false results accidentally. Tell your doctor before taking any test that you are using Flagyl  

Where can you buy Flagyl? 

Flagyl is available to purchase online or offline from pharmacies provided that you have a prescription for your treatment.  

Can I get Flagyl without a prescription? 

Flagyl is not available at this time without a prescription. Speak to a medical professional to ensure that Flagyl is the right treatment for you. If this is not the treatment that is best for you, then a medical professional may be able to suggest an alternative option.  


Medicines.org (2019, September, 18 ) Flagyl 400mg Tablets Retrieved March 27th 2020 from: https://www.medicines.org.uk/emc/product/9238/pil 

Medicinenet (2019, October 2022 ) metronidazole Retrieved March 27th 2020 from: https://www.medicinenet.com/metronidazole/article.htm 

RXList, (2018, June 03) FLAGYL Retrieved March 27th 2020 from: https://www.rxlist.com/flagyl-drug.htm 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.