Metronidazole For Dogs: Everything You Need To Know

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As pet parents, we feel the most at ease when we know our pets are healthy and thriving. We do our best to monitor for signs of illness, whether it’s examining the stool of our dogs before picking it up or checking our dog’s gums for swelling and redness. 

Unfortunately, sometimes we do notice that something is wrong. From diarrhea to swollen gums, there is usually an underlying cause. You might wonder why your dog has diarrhea or swollen gums and what to do about it. Oftentimes, the culprit is an infection, including bacteria and parasitic infections. Taking your dog to the vet as soon as you observe discomfort and getting an accurate diagnosis can ensure that your dog gets the help they need and starts to recover as soon as possible. 

If your dog’s illness is the result of an underlying bacterial or parasitic infection, your vet may prescribe a variety of medications including metronidazole. Metronidazole is an extra-label antibiotic and antiprotozoal used to treat a variety of infections in dogs. Read on to learn about how it is given to dogs, its side effects, metronidazole overdose, and more. 

What Is Metronidazole?

Metronidazole is an off-label medication used to treat anaerobic bacterial and protozoal infections in dogs

Metronidazole (brand name Flagyl) is a human-grade medication used to treat a wide range of infections in humans and pets.1 It has both antiprotozoal and antibacterial properties.2 Since it's not an FDA-approved veterinary drug, vets use it as an off-label medication. 

Metronidazole can also be used for a wide range of other animals, including cats and horses. It's typically prescribed in combination with other medications, depending on the diagnosis.3

Metronidazole targets a specific type of bacteria called anaerobic bacteria, which doesn’t need oxygen to survive in the dog's intestinal tract.4 

What Is Metronidazole Used To Treat In Dogs?

Metronidazole for pets targets anaerobic bacterial infections. These infections may include abscesses, peritonitis, genital tract infections, periodontitis, osteitis, arthritis, and meningitis.2 In addition, dog Flagyl targets protozoal or parasitic infections, such as trichomoniasis, amebiasis, and giardiasis.2 

This medication targets bacteria by disrupting its DNA, although how it eliminates parasites in dogs is unknown.4 In addition, metronidazole is used to treat inflammation of the digestive tract by blocking inflammatory mechanisms.4 

Simply put, metronidazole for dogs can be used to successfully treat: 

  • Parasitic infections of the digestive tract
  • Inflammatory bowel disease (IBD)
  • Oral and dental infections that may affect the digestive tract
  • Bacterial infections that cause diarrhea3

In most cases, it's used to treat severe diarrhea in dogs and may be prescribed even when the cause of diarrhea can't be determined. It's also used for oral infections because of its anti-inflammatory properties. 

How Is Metronidazole Given To Dogs?

Metronidazole is often prescribed alongside other antibiotics and can be administered orally, topically, or by injection

Dog metronidazole is sometimes prescribed with other antibiotics, depending on the dog's initial diagnosis.3 It's a prescription drug, so you can't order it online without first talking to a vet. Depending on your dog's needs, it's available in oral, topical, or injection (IV) form. In most cases, your vet will prescribe the oral form, and you'll give it to your dog based on their instructions with food. If it is prescribed topically, it will likely be given rectally, which enhances absorption.2

The dosage will depend on your dog's breed, size, and the type of infection or illness being treated. For example, dogs suffering from giardiasis typically get a dosage of 25 mg/kg every 12 hours for five days. Meanwhile, dogs with inflammatory GI issues or IBD will receive 10-15 mg/kg every 12 hours.2 In general, the dose ranges from 5-20 mg/kg of body weight, but it mainly depends on what's being treated. It's important to follow the vet's instructions to ensure you're giving your dog the correct dosage at the right times. In addition, you should never give human doses of metronidazole to dogs. Even though they're the same medication, your vet will provide you with the right dosages and instructions to prevent potentially dangerous overdoses. 

Metronidazole is bitter, so you may need to find ways to entice your dog to swallow them. In most cases, masking the pill in a piece of cheese should help, but if you have issues administering the medication to your pet, you can call your vet for advice. 

The medication takes effect within a few hours, and you should notice gradual improvements after a few days. 

What If I Miss Giving My Dog A Dose Of Metronidazole?

Missing a dose of dog metronidazole should not have any adverse side effects. You can give your dog their dosage as soon as you remember. However, if the next dose is only a few hours away, you can skip the missed dose and resume your normal schedule. You should avoid giving your dog extra or double doses of metronidazole because their dosage depends on their weight and health condition, so too much could harm their health.4

What Are The Possible Side Effects Of Metronidazole For Dogs?

Flagyl for dogs is considered relatively safe, and there are no adverse side effects commonly associated with the medication. However, if you give your dog too high a dose, they can experience signs of neurotoxicity, with symptoms such as:

  • Tremors
  • Muscle spasms
  • Ataxia
  • Convulsions

Giving your dog too much of the IV form of metronidazole for dogs can lead to central nervous system (CNS) excitement. Bone marrow depression has also been reported in dogs that take too much metronidazole, but it is reversible. In addition, dogs taking metronidazole may have a reddish-brown discoloration of urine due to pigments in the medication.2

However, like with any medication, you should always monitor your dog for signs of allergic reactions. Symptoms of allergic reaction to medication in dogs include:

  • Hives and rash
  • Rapid heartbeat
  • Difficulty breathing

Dogs may also experience minor side effects from taking Flagyl, including: 

  • Nausea
  • Vomiting
  • Diarrhea
  • Drooling
  • Gagging
  • Fatigue
  • Loss of appetite
  • Fever3

However, in general, side effects of metronidazole for dogs are rare. Since it's a short-acting medication, your dog's symptoms should subside within a day after they stop taking the medication. Additionally, most minor side effects should improve over the course of your dog's treatment. However, if you're worried about your dog's side effects, you should contact your vet to let them know and determine whether your dog should stop or continue treatment. 

What Dogs Should Not Use Metronidazole?

Metronidazole is considered a safe medication for healthy dogs. However, some dogs should not take this medication because it can be harmful to their health. For example, pregnant and nursing females and young puppies should not take metronidazole. Dogs with kidney disease, liver disease, and other underlying health conditions are also not ideal candidates for the drug.3 In general, dogs that should not take metronidazole include:

  • Pregnant and nursing females
  • Dogs with an allergy to the medication or related drugs
  • Dogs with weakened immune systems
  • Puppies and young dogs

In addition, some drugs may interact with Flagyl, including supplements, flea medications, chemotherapy drugs, and more. If your dog is on other drugs, whether they're supplements or prescriptions, you should tell your vet to ensure they won't experience any adverse reactions that may cause one drug to become ineffective or even harmful to your dog's health. 

Metronidazole Overdose

When to seek veterinary attention for metronidazole overdose

If you follow your vet's instructions on the medication label, you can avoid harmful overdoses. Overdoses are a medical emergency, so if you notice any of these symptoms, take your dog to the nearest emergency vet clinic as soon as possible:

  • Vomiting
  • Decreased appetite
  • Neurologic symptoms like seizures4
  • Tremors
  • Stiffness or muscle spasms
  • Dilated pupils3

Because metronidazole for dogs tastes bitter, it's likely your dog will not try to eat it if you drop it on the floor. However, since dogs are curious creatures, you should always keep their pills out of reach to ensure they don't accidentally eat them. If your dog takes more Flagyl than they're supposed to, they'll require immediate treatment to limit the medication absorption and minimize potentially harmful symptoms like seizures.4

Metronidazole For Dogs: FAQs

How should metronidazole be stored?

Metronidazole for dogs should be stored at room temperature; typically, anything between 59 to 77 degrees Fahrenheit is okay. However, you can confirm storage requirements by reading the label, and it's best to keep it in a dark, dry area where you keep the rest of your medications and supplements.4 In addition, you should always keep medication out of reach of children and pets. Even though overdoses are rare because this medication is bitter, it's not worth the risk. Therefore, keep your medication in a cabinet or closet where your children and pets can't reach them. 

Is metronidazole an antibiotic for dogs?

Yes, metronidazole, also known as Flagyl for dogs, is a popular antibiotic used by vets to treat diarrhea and inflammation issues in the digestive tract. It can even be used to treat gum disease since it targets bacteria. Unfortunately, the most common side effect of metronidazole is diarrhea, even though it's often prescribed to treat diarrhea while eliminating bacteria and parasites that may cause the symptom. 

Are there any drug interactions with metronidazole?

There are several drug interactions with metronidazole, including chemotherapy drugs, gastro protectants, other anti-inflammatory drugs, anticonvulsants, and anticoagulants. If your dog is on any other medication your vet may not know about, you should inform them as soon as possible to help them come up with the best treatment plan for your dog. 

Dog laying on table receiving check up from veterinarian

Final Notes

Even though metronidazole is not FDA approved for veterinary use, it's still an effective treatment for many infections by bacteria and protozoan parasites, especially infections in the digestive tract. Diarrhea and other digestive issues can have many underlying causes. It's important to speak to your vet about your dog's diet, exercise, and lifestyle, especially if they suffer from chronic diarrhea with no clear underlying cause. 

Worried about your dog's diarrhea? Talk to a Dutch vet. We can help you fix your dog's nutrition, learn about why dogs have diarrhea, diagnose the underlying cause of your dog's GI issues, and help you treat them, with or without medication. With Dutch telemedicine for pets, there's no need to stress your dog out by going to the vet, potentially making their diarrhea worse. Instead, you can get them the treatment they need from the comfort of home. 



  1. "Flagyl Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing." WebMD, WebMD,

  2. Mercer, Melissa A. "Nitroimidazoles Use in Animals - Pharmacology." Merck Veterinary Manual, 18 Oct. 2022,

  3. "Fat Dogs & Dog Obesity: How to Help Your Dog Lose Weight." American Kennel Club, 4 June 2021,

  4. “Metronidazole.” PetMD,

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