Woman inspecting with magnifying glass, thinking she may have BV | e-surgery

What are some of the Metronidazole Side Effects?

If you are one of the many women who suffer from bacterial vaginosis (BV), you may be prescribed antibiotics such as Metronidazole. Before taking this medication, it is important to understand the potential side effects. This article will discuss common and serious side effects associated with Metronidazole, as well as what to do when you experience them.

What Is Bacterial Vaginosis?

Bacterial vaginosis is a condition caused by an overgrowth of bacteria normally found in the vagina. A microorganism called “lactobacillus” usually keeps the vagina in its acidic state, helping prevent infections. In bacterial vaginosis, there is an increase in certain bacteria called Gardnerella vaginalis [1] and Mycoplasma hominis [2], which release toxins or enzymes which kill other bacteria in the vagina. The lack of competition for space allows this bacterium to outgrow others in the vagina and produce an imbalance. These species of bacteria are also sometimes present in healthy women so it’s difficult to diagnose this infection solely on these bacteria.

Is Bacterial Vaginosis an STI?

Bacterial vaginosis is not a sexually transmitted disease and can affect any woman of childbearing age, although it more frequently affects those who have unprotected and frequent sex, have an IUD (Intrauterine Device), those who douche regularly or are pregnant. Douching washes away natural bacteria inside the vaginal canal so it becomes easier for harmful bacteria or other germs to grow. Certain ethnicities, such as black women, are also statistically more likely to develop the condition. [3]

Bacterial vaginosis is the most common vaginal infection among women ages 15-44 [4]. After menopause, it occurs more frequently because estrogen and progesterone production decreases which allows colonization of harmful bacteria [5].

Is Bacterial Vaginosis the same at thrush?

Bacterial vaginosis can also often be confused with thrush, have a look at our article that compares the two and lets you know how to tell the difference. Here are the most common symptoms of Thrush, as it is important to recognize your symptoms to get the correct treatment. In addition, women should be aware of the differences between a UTI and Thrush, as these conditions are very common and can overlap.

What Are The Symptoms Of Bacterial Vaginosis?

Woman suffering from BV wondering what are the Metronidazole Side Effects

Some women have no symptoms at all – about 50% of all women with bacterial vaginosis don’t (6). If you do experience symptoms, they may include [3]:

  • A strong fishy odor coming from the vagina
  • An increase in vaginal discharge, which may appear white or grey
  • Pain or burning during urination

What Are Metronidazole Tablets?

Metronidazole tablets are prescription medications used to treat bacterial vaginosis (BV) in adult women. Metronidazole is an antibiotic that treats the overgrowth of ‘bad’ bacteria by targeting it with an antimicrobial agent. Metronidazole is effective against anaerobic microorganisms, such as those that cause BV. It works by stopping the growth of bacteria and allowing the body’s natural defenses to take over and restore normal vaginal flora.

What Are Metronidazole Side Effects?

Some antibiotics, including Metronidazole, have serious side effects that could harm you. It’s important for you to know what side effects might happen before taking this medicine so that you can avoid them or seek medical attention right away if you do have any symptoms.

Common Metronidazole side effects may include [7] [8]:

  • Headache
  • Vomiting
  • Loss of appetite
  • Heartburn or acid reflux
  • Constipation
  • Gastrointestinal issues or diarrhoea.
  • Abdominal cramps
  • Metallic taste in the mouth
  • A feeling of being sick
  • Vaginal discharge/Yeast infection

These Metronidazole side effects are typically mild and will likely go away once you stop using the medication.

Severe Metronidazole side effects though rare can be life-threatening for certain individuals. Please be aware that your GP/Pharmacist will only prescribe this medication if it is safe to do so, and will be happy to answer any concerns you may have. You can connect with an e-Surgery pharmacist online for free using our Ask-a-Pharmacist service. Those that require immediate medical attention include:

  • Eyes or skin turns yellow indicating liver or gallbladder issues.
  • Unexpected infections begin appearing.
  • You may experience blood issues such as bruising, mouth ulcers, bleeding from gums, excessive tiredness, etc.
  • Pancreatic issues such as severe stomach and backache.
  • Blurred vision.
  • Signs of meningitis such as severe headache, intolerance to bright lights, hallucinations, stiff neck, and fever.
  • Symptoms of peripheral neuropathy such as the feeling of pins and needles, numbness, a feeling of burning, and stinging pains.
  • Neutropenia, which is a condition of low neutrophils, are important cells that help the body fight off infections. A person with neutropenia has an increased risk of developing bacterial, fungal, and viral infections. It will go away once the medication is stopped.
  • Cancer.
  • It May cause seizures. Those with a seizure history should consult their GP before taking this medication.
  • A severe allergic reaction.
  • Stevens-Jones syndrome with symptoms including fever, followed by a painful rash, and then shedding of the skin’s top layer.

Where Can I Purchase Metronidazole Tablets?

You can easily and securely purchase Metronidazole tablets for bacterial vaginosis from e-Surgery, a registered and reputed online pharmacy.

It is available as a 7-day course, with one 400mg tablet to be taken twice daily on a full stomach. Avoid alcohol consumption while on the antibiotic course and till 48 hours after finishing the medication.


Although Metronidazole tablets are a common and effective treatment for bacterial vaginosis, they may cause some side effects. It is important to be aware of these potential side effects before you begin taking the medication.

Before beginning any medication, let your GP know so that you don’t experience any cross-medications. Talk to your doctor if you experience any of the above side effects. If a severe or rare side effect occurs, stop using Metronidazole and contact your doctor immediately or seek emergency medical assistance.

Further Reading

  1. Metronidazole Oral: Uses, Side Effects, Interactions | WebMD
  2. Side effects of metronidazole | NHS
  3. Metronidazole Side Effects | Healthline
  4. Metronidazole (Flagyl) – Side Effects, Interactions, Uses | Everyday Health


  1. Gardnerella – StatPearls – NCBI Bookshelf | NCBI
  2. Mycoplasma hominis and Gardnerella vaginalis display a significant synergistic relationship in bacterial vaginosis | NCBI
  3. Bacterial Vaginosis: Symptoms and How to Treat It | Healthline
  4. Infections in Pregnancy: Bacterial Vaginosis | Healthline
  5. Probiotics in the Prevention and Treatment of Postmenopausal Vaginal Infections: Review Article | NCBI
  6. Bacterial vaginosis – NHS | NHS
  7. Metronidazole Side Effects: Capsules, Gel, Alcohol, and More | Healthline
  8. Side effects of Metronidazole – NHS | NHS