Metronidazole For Dogs: Dosage, Uses, And Side Effects

Medically reviewed by Nicole Wanner, DVM

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If your dog is suffering from diarrhea, inflammatory bowel disease, tooth or gum disease, or parasites, your vet may prescribe a drug called Metronidazole (Flagyl).

In this blog, we explore the uses, dosage, and side effects of Metronidazole for dogs.


Metronidazole is a strong antibiotic used to treat bacterial infections and some parasites, and is often prescribed with other antibiotics. 


Metronidazole should start to work in around one to two hours, though you may not notice the effects that fast. It can take a few days for a gradual improvement in symptoms to be visible.  


Metronidazole is most often prescribed by vets to treat severe diarrhea in dogs. It is also used frequently for dental infections due to its ability to move through bone. Its anti-inflammatory effects also make it useful in the treatment of inflammatory bowel disease. Here is a list of the most common uses for Metronidazole in dogs: 

  • Diarrhea
  • Inflammatory bowel disease (IBD)
  • Bacterial Infections
  • Parasites
  • Periodontal disease


Yes, there are potential side effects of Metronidazole for dogs. If your dog is experiencing any of the following, you should immediately get them to the vet:

  • Hives
  • Labored Breathing
  • Swelling around the face or tongue

Call your vet and monitor your dog closely if you notice any of these side effects: 

  • Diarrhea
  • Lethargy
  • Seizures
  • Vomiting
  • Poor balance
  • Weakness
  • Not eating
  • Bloody urine
  • Yellow tint to whites of eyes


If you are talking to your vet about Metronidazole for your dog, it's important to let them know about any vitamins, supplements, or herbal remedies your dog is taking.

The following drugs can have potentially harmful interactions if taken with Metronidazole, so you should make your veterinarian aware if your dog is taking any of them: 

  • Chemotherapy medication
  • Gastroprotectants (cimetidine)
  • Cyclosporine
  • Phenobarbital
  • Phenytoin
  • Warfarin

Make sure to inform your vet if your dog is in any of the following situations: 

  • Is taking medication to thin the blood
  • Is pregnant
  • Is under three months old
  • Has liver problems

Your vet may avoid prescribing this medication if your dog has any of the following:

  • Nursing puppies
  • Allergic or sensitive to Metronidazole or similar drugs
  • Weakened immune system

It’s important to note that some studies have found that Metronidazole may be harmful for pregnant women. The jury is still out, though. If you accidentally touch it, you should immediately rinse it off.


The generally accepted dose range is 5-20mg per kg (2.2lb) of your dog's body weight. Metronidazole is a prescription drug, so your vet will advise you on the correct dosage and schedule. Make sure you follow their instructions very closely, as though Metronidazole is prescribed to dogs regularly; it is not FDA approved for use in animals. You will usually find Metronidazole in either 250mg or 500mg pills. However, it is also available in capsules, liquid suspensions, and can be made into a flavored liquid by a compounding pharmacy. The flavoring can be useful if you have a dog who refuses to eat tablets. If you miss a dose of Metronidazole, you can give it to your dog when you remember, as long as it isn't too close to the next scheduled dose. Never give two doses to your dog at the same time.


Metronidazole costs around 34c for a 250mg tablet and 62c for a 500mg tablet, making it relatively inexpensive. A compounded liquid suspension usually starts at around $50.  



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Ever since she was a puppy, she’d spend her days running and playing. I’d take her on walks, to the beach, and dog parks.

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