Metronidazole Side Effects: Everything You Need To Know

If you suffer from Bacterial Vaginosis (also known as BV), you’ve probably heard of Metronidazole. This prescription-only antibiotic is extremely effective at treating BV — and Metronidazole side effects are also very uncommon.

Although the risk of encountering Metronidazole side effects is usually low, it is always worth finding out more about any medication and how it could potentially affect you before starting any course of treatment.

On this page, we’ll be talking about the side effects of Metronidazole in detail — from more common side effects to the more serious, as well as how to cope with any potential reactions. Read on to find exactly what to expect if you decide to use this BV treatment.

For more general information about Metronidazole, visit our ‘What is Metronidazole?’ page.

Metronidazole 400mg Tablets

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Metronidazole side effects

Everybody is different, which means that we can all react to the same medicine in different ways. Most users don't experience any negative Metronidazole side effects at all and should have a very positive experience with the medication.

However there is always a chance that side effects could occur — whether they are the more common side effects, or the more unusual.

Here is a summary of the known side effects of Metronidazole (most of these are very rare):

• Feeling sick (nausea)
• Being sick (vomiting)
• Upset stomach or diarrhoea
• Loss of appetite
• Numbness, tingling, pain or a feeling of weakness in the arms or legs
• Metallic or unpleasant taste in the mouth
• Furry tongue
• Fever
• Feeling depressed
• Pain in your eyes (optic neuritis)
• Anaphylactic reactions
• Abnormal laboratory test results
• Blood and bone marrow problems
• Brain and central nervous system problems including neurological problems. Seek medical advice if you have symptoms such as fever, paralysis, photosensitivity, balance or coordination problems, stiff neck, tremors or epileptic seizures
• Convulsions
• Double vision
• Eye or eyesight problems
• Feeling dizzy
• Feeling drowsy
• Flushing
• Headaches
• Itching
• Jaundice
• Joint pain
• Liver problems
• Muscle pain or tenderness
• Myopia
• Pancreatitis
• Psychotic problems including confusion and hallucinations
• Skin problems
• Skin rash
• Urine colour changes (your urine may get darker in colour)

These side effects range from what is thought to be milder and more common side effects of Metronidazole (such as nausea - around 1 in 10 people) to very rare (such as psychotic problems). The likelihood of experiencing any of these side effects can vary from user to user; what one individual may encounter could be completely different from another.

If you are concerned about any reactions or Metronidazole side effects you are experiencing (particularly if they feel severe, long-lasting or painful), then you should consult your doctor for further guidance.

More common side effects and symptoms

Many of the Metronidazole side effects we’ve listed above will not be experienced by the majority of users.

However, there are some more common side effects of Metronidazole tablets that are more likely to occur.

The most common may include headaches, nausea, vomiting, an upset stomach, diarrhoea, constipation, loss of appetite, abdominal pains, heartburn, a metallic taste in the mouth, and a furry tongue.

It is worth noting that these more common side effects usually do not need medical attention and that most people have no problems taking this widely used medicine for a week-long course. These side effects will usually go away during treatment as your body adjusts to the medicine.

Serious side effects and symptoms

Serious side effects of Metronidazole are very unusual but may happen.

Below, we have listed some of the more unlikely but serious side Metronidazole effects and symptoms:

• Seizures
• Mental/mood changes (such as confusion)
• Unsteadiness
• Numbness or tingling in your hands or feet
• Blurred or double vision (or any other vision changes like light sensitivity)
• A fever (38C and above), stiff neck, difficulty speaking, hallucinations and confusion (these can be warning signs of meningitis or something else serious)
• Intense stomach pains which may reach through to your back
• Yellow skin or the whites of your eyes turning yellow (this could be indicative of liver or gallbladder problems)
• Unexpected infections such as mouth ulcers, bruising or bleeding gums (which may be indicative of a serious blood problem)

Stop taking the tablets and tell your doctor straight away if any of these unlikely but serious side effects occur.

Allergic reactions to Metronidazole

A serious allergic reaction to Metronidazole tablets is very rare, but it can happen.

Seek immediate medical attention if you notice any of the below symptoms of a serious allergic reaction:

• Any skin rashes (including itchy, red, swollen, blistered or peeling skin)
• Tightness in the chest or throat
• You have trouble breathing or talking (such as breathlessness or wheezing)
• Swelling (particularly of the face, tongue or throat)
• Severe dizziness

These are the symptoms of a serious allergic reaction to Metronidazole, and you should treat this as an emergency — get emergency medical attention immediately by calling 999.

How long do Metronidazole side effects last?

Most Metronidazole side effects shouldn’t last that long.

Usually, they will start from relatively soon after you take a tablet, and should be over in between 30 minutes to several hours (or potentially longer), depending on the type of side effect you experience.

The length of time you experience side effects will vary depending on how your body naturally reacts to the medication; every individual is different, meaning we can all react to the same medication in different ways. This may also vary depending on whether you’ve taken the Metronidazole tablet with food or without.

If the side effects don’t go away, you should talk to your doctor or pharmacist.

How to cope with Metronidazole side effects

If you’re worried about suffering from Metronidazole side effects during your course of treatment, there are a few things you can do to reduce the likelihood of experiencing side effects, as well as the severity of side effects.

These tips will help you to cope with the most common Metronidazole side effects:

• Some people feel sick or may be sick (vomit) when they take Metronidazole. To prevent stomach upset, nausea and vomiting, take this medication with food (either a meal or a large snack). You can take the tablets with or without food, but having a full stomach will help to ease feelings of nausea.
• If you have been experiencing feelings of nausea, diarrhoea or lightheadedness, then you should drink plenty of fluids like water or squash. This will help to keep you hydrated. However, it’s important to sip this slowly rather than drinking large quantities at once; this may make you feel even more sick.
• You may want to stay away from particularly rich or spicy foods if you are suffering from stomach upsets as a Metronidazole side effect; stick to simple and plain food instead.
• A metallic taste in your mouth or a furry tongue are common side effects when taking Metronidazole. If this becomes unpleasant for you in anyway, drink some flavoured liquids like squash, or eat some simple food that you enjoy. This will help to detract from the flavour in your mouth.

As we know, it is important to avoid alcohol whilst taking Metronidazole and for at least 48 hours after your course has finished to avoid any severely unpleasant side effects (nausea and vomiting are much more likely to occur).

If this happens, sip on water to ease feelings of nausea. Make sure you sit down and avoid any sudden movements to help with any lightheadedness you have from flushing, dizziness and increased heart rate.

If your symptoms persist or become worse, you should seek medical help.

It is strongly recommended by medical professionals that you do not use Metronidazole alongside alcohol. This is because Metronidazole is known to react badly with alcohol and can cause a number of unpleasant side effects.

For more information, you can go to our Metronidazole and alcohol page.

When you need to see a doctor

If you have been taking Metronidazole to treat BV and you are concerned that any reactions or side effects you are experiencing are abnormal (especially if they persist or get worse), then you should consult your doctor for further guidance. You may need to stop the treatment, but it is best to talk to your doctor or pharmacist as this could impact the effectiveness of the medicine.

Call your doctor immediately if you experience the below unlikely but serious symptoms:

• Seizures
• Mental/mood changes (such as confusion)
• Unsteadiness
• Numbness or tingling in your hands or feet
• Blurred or double vision (or any other vision changes like light sensitivity)
• Difficulty speaking
• A fever (38°C and above) and stiff neck
• Intense stomach pains which may reach through to your back
• Hallucinating (you're seeing or hearing things that aren't there)
• You get yellow skin or the whites of your eyes turn yellow (this could be indicative of liver or gallbladder problems)
• You get unexpected infections such as mouth ulcers, bruising or bleeding gums

Seek urgent medical help straight away if any of these unlikely but serious side effects occur:

• Any skin rashes (including itchy, red, swollen, blistered or peeling skin)
• Tightness in the chest or throat
• You have trouble breathing or talking
• Your mouth, face, lips, tongue or throat start swelling

These are the symptoms of a serious allergic reaction to Metronidazole, and you should treat this as an emergency.

If you are pregnant and wish to use Metronidazole, you should consult your doctor first; for more on this, go to our Metronidazole while pregnant page.

Summary

Metronidazole is a very safe and effective antibiotic medication used to treat bacterial vaginosis (BV). Many users will not experience any negative Metronidazole side effects at all and will have a very positive experience with the medication on the whole.

However, as with any medication, there is always a chance that side effects could occur — whether they are the more common side effects, or the more unusual.

You are most likely to experience mild side effects when taking Metronidazole: primarily, some stomach upsets and nausea, a metallic taste in the mouth, and a furry tongue. On the whole, these do not need medical attention — but if you are unsure or concerned in anyway, you should contact a doctor, pharmacist or another medical professional.

You can buy Metronidazole at The Independent Pharmacy using our secure and discreet online service. It’s very easy, and free to do; all you need to do is fill in a short online questionnaire before we deliver your treatment straight to your door.

Sources

• Metronidazole 400mg Tablets Patient Information Leaflet: https://www.medicines.org.uk/emc/product/9238/pil
• https://www.nhs.uk/conditions/bacterial-vaginosis/
• https://www.drugs.com/metronidazole.html