Metanidazole Side Effects

Metronidazole can be an effective medication for many people with conditions like rosacea, skin infections, and mouth infections such as dental abscesses and infected gums, as well as pelvic inflammatory disease and bacterial vaginosis. However, like any medication, metronidazole can cause side effects in some people.

While Metronidazole is generally well-tolerated, it can cause mild-to-moderate side effects for some people. Read on to find out more information about the side effects of metronidazole, including how the different ways of taking it – such as oral tablets, capsules, topical creams, gels, and lotions – can have different side effects.

Dr Babak Ashrafi Clinical Lead for Service Development

Medically reviewed by

Dr Babak Ashrafi

Last reviewed: 23 Sep 2023

What Are the Side Effects of Metronidazole?

The side effects people get from taking metronidazole will vary in type and severity from person-to-person. The form of metronidazole also determines the possible side effects. Most frequent side effects of tablets, liquid, suppositories, or vaginal gels are diarrhoea, nausea (feeling sick), vomiting (being sick), and a metallic taste in your mouth. Metronidazole creams and gels do not normally cause side effects, but they can for some people.

Side Effects of Metronidazole Tablets and Capsules

Like any medication, metronidazole tablets and capsules can cause side effects in some people. Whether side effects occur or not depends on the individual taking the tablets.

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

  • yellowing of the skin and eyes
  • severe tiredness
  • unexpected infections
  • mouth ulcers
  • stomach pain

Seek immediate medical attention if you get:

  • swellings of hands, feet, ankles or any other body part
  • problems with breathing
  • an itchy rash or hives
  • a stiff neck
  • headache
  • problems using your arms and legs
  • difficulty speaking and confusion
  • hallucinations

These are very rare side effects, and you need immediate medical attention if you develop any of them.

Side Effects of Topical Creams and Gels

Topical creams and gels containing metronidazole can cause a variety of possible side effects depending on the individual, the type of cream or gel they’re using, and what they’re using it for. Remember that side effects are not experienced by everyone.

Side effects of metronidazole gels and creams used for rosacea

Creams and gels containing metronidazole can be used for the treatment of rosacea, a skin condition that causes reddening of the skin on the face.

The most common side effects include:

  • watering of the eyes
  • skin reddens
  • treated skin lightens in colour
  • burning sensation on your skin after application
  • peeling of skin
  • dry skin
  • greater sensitivity to sunlight

Read the patient information leaflet you receive with your rosacea treatment for more information, or ask your doctor.

Side effects of vaginal gels containing metronidazole

Vaginal gel containing metronidazole is commonly used to treat bacterial vaginosis (BV). Like all medications, vaginal gels containing metronidazole can cause side effects.

Some of the common side effects of metronidazole gel used for BV include:

  • dizziness and headaches
  • nausea (feeling sick)
  • vomiting (being sick)
  • stomach cramps
  • dry skin
  • itchy and/or irritated skin
  • an unpleasant taste in your mouth

Some of the uncommon side effects of metronidazole gel used for BV include:

  • fatigue
  • problems sleeping
  • unusual feeling in your toes and fingers
  • dry mouth or feeling thirsty
  • muscle cramps
  • diarrhoea
  • constipation
  • depression

Some of the rare side effects of metronidazole gel for BV include:

  • numbness, tingling, or a burning sensation in your hands or feet
  • serious allergic reaction

Side effects of vaginal creams containing metronidazole

Sometimes a cream applied directly to the skin, such as Dalacin Cream can be prescribed to treat bacterial vaginosis. Like any medication, Dalacin Cream can cause side effects, although they do not affect everyone.

The most common side effects include:

  • mild itching
  • a vaginal thrush infection
  • irritation in your vagina

Uncommon side effects include:

  • headache
  • vertigo (dizziness)
  • nausea (feeling sick)
  • vomiting (being sick)
  • diarrhoea
  • stomach pain
  • constipation
  • heartburn

There are some more serious side effects, although it is not known how common these are. They can include:

  • blood in your stool
  • severe diarrhoea
  • fever
  • signs of an allergic reaction, like a rash or hives

It’s often recommended to avoid using condoms or contraceptive diaphragms whilst using most vaginal gels. This is because these barrier methods can be less effective and weakened by some gels. Use alternative contraceptive methods during treatment and for at least 5 days after you stop using a vaginal gel.

How Long Do Metronidazole Side Effects Last?

The duration of metronidazole side effects can vary depending on the individual, the dosage, and the specific side effect experienced. In general, most common side effects of metronidazole, such as nausea, vomiting, diarrhoea, and metallic taste in the mouth, tend to be temporary and will go away shortly after discontinuing the medication or completing the prescribed course.

You should always contact your doctor if you get any side effects that you’re struggling to deal with or won’t go away.

If you get any signs of an allergic reaction such as rash, itching, swelling, severe dizziness, or difficulty breathing, you must seek immediate medical attention.

Skin reactions or allergic symptoms may take a bit longer to subside and can persist for several days after stopping metronidazole. If you are experiencing persistent or severe side effects, it is important to consult your doctor for further evaluation and guidance.

Everyone's response to medication can be different, and individual factors can influence the duration and severity of side effects. If you have specific concerns about the duration of metronidazole side effects, speak to your doctor for more advice.

How to Avoid Metronidazole Side Effects

While it's not always possible to completely avoid side effects, there are a few steps you can take to minimise the likelihood or severity of metronidazole side effects:

Check the ingredients on the patient leaflet

Make sure metronidazole does not contain any ingredients that you are allergic to. You can find this information in the patient leaflet that comes with your medication.

Do not take it if you have Cockayne syndrome

Metronidazole can cause life-threatening liver problems for people who have Cockayne syndrome. Contact your doctor immediately if you have this condition and have taken metronidazole.

Follow dosage instructions

Take metronidazole exactly as prescribed by your healthcare provider, paying attention to any intervals between taking tablets or applying metronidazole to your skin. Do not exceed the recommended dosage or alter the treatment duration without medical advice, and finish the course of medication as prescribed unless advised otherwise by a doctor.

Take with food

Taking metronidazole tablets or capsules with food can help reduce the risk of stomach-related side effects such as nausea or abdominal discomfort. The exception to this is if you are taking extended-release capsules, which must be taken without food.

Avoid alcohol

It's important to avoid drinking alcohol while taking metronidazole as it can lead to an increase in severe side effects such as nausea, vomiting, and several other adverse reactions.

Inform your doctor and report any concerns

Make sure to inform your doctor about any pre-existing medical conditions or medications you are taking to help them assess potential interactions or contraindications. If you experience any side effects while taking metronidazole, let your doctor know. They can evaluate your symptoms and make any necessary adjustments to your treatment.

Remember, while side effects can occur, they are normally temporary and may be outweighed by the benefits of treating the infection. Following these precautions and communicating with your doctor can help manage any potential side effects effectively.

When Should I See a Doctor About My Side Effects?

It is important to seek medical attention if you experience any severe or worrying side effects while taking metronidazole. Some circumstances in which you need to consult a doctor include:

Allergic reactions

If you develop symptoms such as rash, hives, itching, swelling (especially of the face, lips, tongue, or throat), or difficulty breathing, it could indicate an allergic reaction that requires immediate medical attention.

Severe or persistent side effects

If you experience persistent or severe side effects that are causing significant discomfort, it is advisable to consult your doctor. This includes getting symptoms like severe nausea, vomiting, diarrhoea, dizziness, headache, or mood changes.

Worsening of symptoms

If your condition being treated with metronidazole does not show improvement or worsens despite completing the prescribed treatment, it is important to consult your doctor for re-evaluation.

New or unusual symptoms

If you develop any new or unusual symptoms that you suspect may be related to metronidazole, it is best to seek medical advice to rule out any potential complications.

In general, it's important to communicate any concerns or persistent side effects to your doctor. They can evaluate your symptoms, provide appropriate guidance, and make the necessary adjustments to your treatment plan.


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