Two Easy Ways to Start Earning Rewards!
Become a member today!
Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
Already a member? Sign in
Become a credit card member today!
Earn 2X Pals Rewards points at Petco
when you use Petco Pay!
APPLY NOW
Learn More About Petco Pay Benefits

My dog is on metronidazole. Can it cause runny stools or diarrhea?

Updated on September 23rd, 2025

Pet's info: Dog | German Shepherd | Female | unspayed | 1 year and 2 months old | 72 lbs

can metronidazole cause runny stools in dogs thanks

3 Answers

Most Helpful Answer

Answered By Daniel Fonza, DVM

Veterinarian

Published on October 22nd, 2017

Hi there and thank you for using pet coach to address your concern. Yes, metronidazole can cause diarrhea. If you are seeing diarrhea or vomiting while on this antibiotic I would recommend discontinuing the drug and contacting the prescribing veterinarian to discuss this further. I hope this helps guide you in the right direction. Please let me know if you have any other questions or concerns. I would add in a probiotics such as Purina fortiflora as well.

2Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Jenny, DVM
Veterinarian
Published on July 31st, 2017
That is a very common antibiotic that is prescribe for loose stool especially if there is blood present. Every medicine has side effects, but the short term use of that particular one has minimal. Most side effects are from prolonged use and often at very high doses.
2Pet Parents found this answer helpful
Answered By Dr. Strydom, DVM
Veterinarian
Published on February 10th, 2018
Hello. Thank you for using Petco Pet Education Center, formerly Petcoach.

It is my recommendation that you keep Loki on all the medications prescribed by your vet. If you want to change the medications you should discuss your concerns with your vet. They have all her medical history and know why they prescribed the medications they did, etc.

Any drug can have side effects and be dangerous. I would not classify Metronidazole as dangerous; it really doesn't cause much in the way of side effects unless they are given a very high dose.

There is a huge issue in veterinary medicine with owners not following through with the entire course of medications they are given: #1 this causes bacterial resistance and then when we really need these drugs they don't work and #2 the infection is not completely resolved so when you stop the drug the dog will often come down with the same issue because the infection was not properly cleared.

Metronidazole is an antibiotic, has anti-protozoal properties and is also an anti-inflammatory for the colon. It is not an anti-diarrheal. The diarrhea resolves because the Metronidazole is killing the protozoan parasites, kills any overgrowth of specific bacteria that cause diarrhea and by reducing colonic inflammation.

Please continue all the medications as directed and call your vet on Monday if you want to discuss stopping the Metronidazole.

Hope this helps. Best wishes and I hope Loki gets better soon!
1Pet Parents found this answer helpful

Smart Picks for Smart Questions

Related Questions

Health & Wellness

Is my dog's Metronidazole causing diarrhea or other side effects?

Sorry Jake is having problems. Metronidazole is often used to treat diarrhea in dogs. It is not common for metronidazole to cause vomiting. However, the underlying CAUSE of the diarrhea is usually some form of gastroenteritis which is inflammation of the stomach and intestine. Gastroenteritis often includes vomiting and can occur for many reasons including: bacterial imbalance, viral infections such as parvovirus (Jake is too old for this to be a concern) ingesting non-food items such as trash or mulch inflammatory bowel disease cancer in the GI tract intestinal parasites At higher doses, metronidazole can cause "grogginess" or an unsteady gait. If he is showing those signs, discontinue the metronidazole. Correct, I would hold off on Pepto, but Pepcid AC is fine. I hope I've answered your questions, and I apologize that we did not get to your question sooner. Please feel free to post again if you still have questions or concerns with Jake. Thanks for asking Petco Pet Education Center, formerly Petcoach!

Updated on September 23rd, 2025

Health & Wellness

My dog got diarrhea after starting new medication. Is it a side effect?

Thank you for submitting your question regarding Indy. No, diarrhea is not a common side effects from these medications. Metronidazole, in particular, is used to treat diarrhea. I recommend contacting his veterinarian with the update on his new symptoms. If he is otherwise doing well, it may be recommended to fast him for a period of time to allow his GI tract to rest. I hope this information helps!

Updated on September 23rd, 2025

Is soft puppy stool normal after metronidazole for diarrhea?

Hi! I would say that it is likely ok. Sometimes it takes a bit longer to see results. If it is just soft and Snowball is otherwise fine, I would just give it a few days before getting concerned. Keep in mind that metronidazole is not always a curative medication for diarrhea but rather an antibiotic with anti-inflammatory properties that help with colitis. This means that it will not treat an underlying disease every time. Perhaps try a few days on a bland diet mostly composed of boiled chicken or turkey and rice. If no resolution within a few days, it may be appropriate to start her on a probiotic or try a different medication such as Tylosin. Best of luck with her!

Updated on September 23rd, 2025

Health & Wellness

Why is my dog's poop yellow after metronidazole for diarrhea?

I agree that this poop is quite a bright color yellow! This is not normally caused by metronidazole, so it's hard to say why it might be happening. Poop can sometimes be yellow or orange in color, and it may not mean anything in particular... so I wouldn't necessarily be concerned unless it stays this was for several days in a row, or she's having other symptoms of a problem. If she's still acting normal and this stool is improved vs. yesterday (which I'm assuming it is, since it definitely looks better than bloody diarrhea!) it should be okay to continue on her meds as prescribed by your vet, and monitor for the next few days. If her stool is not back to normal within the next 3-5 days, or if she develops other new symptoms in the meantime, then I would recommend having her rechecked by your veterinarian.

Updated on September 23rd, 2025

Health & Wellness

My pet's diarrhea got worse on Metronidazole. Should I stop?

It could be that the diarrhea worsening is independent of the metronidazole as this drug does not help all cases of diarrhea, dependent on the cause. But since it is new it would be best to stop until you can speak with your vet. Has your kitty had a work up for these symptoms? Chronic vomiting and diarrhea are common symptoms of several things, but most notably GI disease. It would be abnormal for a cat to need chronic medication for vomiting unless there is a disease process there. Just to help a little, a work up for an older kitty with these signs could include bloodwork with thyroid testing, an abdominal ultrasound, and sampling if needed (dependent on ultrasound). If there is an underlying disease that can be treated your kitty may feel better and need less medications eventually. I hope this helps and thank you for using Petco Pet Education Center, formerly Petcoach!

Updated on September 23rd, 2025

My dog's diarrhea keeps returning. Is long-term Flagyl safe?

Some dogs that have an underlying disease like inflammatory bowel disease do need long term antibiotic use, but it is best to have a diagnosis before continuing medications long term for two reasons: one is that antibiotic usage can sometimes mask the underlying problem, and the other is that there can be effects on the gastrointestinal flora. There are many diseases that could cause chronic diarrhea including a food intolerance, pancreatitis, or inflammatory bowel disease as stated above. I would recommend talking to your veterinarian to see if other tests or treatments are recommended at this point to try to diagnose the problem - some additional tests might include a pancreatic lipase test, cobalamin/folate, abdominal ultrasound or even obtaining intestinal biopsy samples to try to determine what might be causing chronic diarrhea. You might also want to talk to your veterinarian about a hypoallergenic food trial.

Updated on September 23rd, 2025

My dog's diarrhea worsened on meds. Can I give Loperamide or Flagyl?

It would be best to consult with your veterinarian before changing treatment or giving other medications. Legally, we are prohibited from recommending medications or dosing information in the absence of a physical exam and a patient-veterinarian-client relationship. You can try withholding food for 24 hours. Allow small amounts of water or an unflavored electrolyte replacement beverage. Resume feeding a bland diet in small frequent amounts until symptoms resolve. Transition slowly to the regular diet afterwards. A stool sample should be submitted to diagnose intestinal parasites or bacterial overgrowth. A veterinary probiotic such as Prostora, FortiFlora or ProViable may promote gut health.

Updated on September 23rd, 2025

Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Share