1. Health
You can opt-out at any time. Please refer to our privacy policy for contact information.

Side Effects of Flagyl (Metronidazole)

This Antibiotic Is Used To Treat Infections And Pouchitis


Updated June 16, 2014

Young woman sitting on bed with headache

Flagyl can cause several troublesome side effects such as headache and dry mouth.

Tetra Images/Brand X Pictures/Getty Images

Common Side Effects of Flagyl

Check with your doctor if any of the following side effects continue or are bothersome:

  • diarrhea
  • dizziness or lightheadedness
  • headache
  • loss of appetite
  • nausea or vomiting
  • stomach pain or cramps

Less Frequent or Rare

Check with your doctor if any of the following side effects continue or are bothersome:

  • change in taste sensation
  • dryness of mouth
  • unpleasant or sharp metallic taste

Check With Your Doctor

Less common

  • any vaginal irritation, discharge, or dryness not present before use of this medicine
  • clumsiness or unsteadiness
  • mood or other mental changes
  • skin rash, hives, redness, or itching
  • sore throat and fever
  • stomach and back pain (severe)

For injection form

  • Pain, tenderness, redness, or swelling over vein in which the medicine is given

Notify Doctor Immediately

Less common

  • numbness, tingling, pain, or weakness in hands or feet


  • convulsions (seizures)

Other Notes

Metronidazole (Flagyl) may cause dark urine in some patients. This is temporary and will go away when you stop taking this medicine.

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor. This information is meant only as a guideline - always consult a physician or pharmacist for complete information about prescription medications.

Return to Medication Side Effects Index

©2014 About.com. All rights reserved.

We comply with the HONcode standard
for trustworthy health
information: verify here.