Probiotics are supplements that contain beneficial microorganisms that can help improve certain health conditions in dogs. Pet owners and veterinarians often use them to promote gut health in dogs. Probiotics have become a common part of many people’s and their pets’ healthcare routines.

Some dog owners wonder if a dog can overdose on probiotics. There are many internet articles on the topic written by laypeople that don’t give the full picture. As a veterinarian, I have a few concerns I want to share with you.

Although uncommon, a dog can get an overdose of probiotics. Dogs who accidentally eat a huge amount of the supplement can develop mild to severe digestive upset. Immunocompromised dogs may even develop a bacterial infection in their blood from a normal dose of probiotics.  


  • Dogs who eat a massive quantity of probiotic supplements may develop symptoms.
  • Probiotics made for humans may contain the sweetener xylitol which is highly toxic to dogs.
  • For best results, follow your vet’s recommendations for dosing your dog with probiotics. If they accidentally get an overdose, your vet can also help with treatment.

What’s the Proper Dosage of Probiotics for Dogs?

Scientists are still trying to establish the proper dosage of probiotics for dogs. You have to give enough good bacteria that some will survive the digestive chemicals in the stomach. But if too many are given, dogs can develop adverse effects (see below for details).  

The most common dosing range for dog probiotics is between 100 million to 100 billion colony-forming units (CFUs) of beneficial bacteria and microorganisms per dose. (2)

Let’s look at two popular veterinary-recommended dog probiotics. Pro Plan Fortiflora® has 100 million CFUs per dose. NutraMax’s Proviable DC® has at least 5 billion CFUs per dose. 

You can certainly find probiotics with a lot more CFUs per dose, but more is not always better. 

I recommend my clients stick to using probiotics made specifically for dogs and are produced by trustworthy manufacturers. ProPlan Fortiflora and Nutramax Proviable DC are two my clients have relied on for many years. Use the dose recommended on the label unless directed by your veterinarian to do otherwise.


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Dogs like Lucy will gobble anything edible, including supplement pills!

How Many Probiotics Would Cause an Overdose in a Dog?

Just how many probiotics does it take to cause problems for a dog? Scientists don’t know the answer. Since probiotics seldom cause major problems for dogs taking them, there are no scientific studies that have tested a maximum dose. 

And since every dog is different, some may not have any problems at all with 10 times the recommended dose while others could get sick enough to need treatment. 

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Factors that May Increase the Risk of Probiotic Overdose in Dogs

There have been reports of humans getting very sick from recommended doses of probiotics. (5) The risk may be increased in people with compromised immune systems and/or inflammation of the digestive tract.

No studies have looked at dogs with the same conditions, but they might have the same risks. My advice? If your dog has immune system disease or chronic GI tract inflammation consult your vet before giving them any probiotic supplements at all.

Watch Out for Human Probiotics with Xylitol Sweeteners

There are many chewable human probiotics made for children that contain the sweetener xylitol. Xylitol is safe for kids but VERY TOXIC TO DOGS.  

If your dog has eaten a probiotic supplement containing xylitol, it doesn’t matter if they only ate a small amount. Even small amounts of xylitol cause extreme blood sugar and liver problems in dogs very quickly. You need to seek veterinary care immediately. 

Can a dog overdose on probiotics

Probiotics Overdose Symptoms in Dogs

Dogs can experience adverse effects from probiotic supplements even at recommended doses. The most common side effects are constipation, increased gassiness, nausea, skin rash and hiccups. Dogs with sensitive stomachs, chronic pancreatitis, etc. may be more likely to be affected.

With massive overdoses, we might expect to see diarrhea, abdominal pain, poor appetite and/or vomiting. Infections could theoretically occur in some dogs, which might cause symptoms such as fever, weakness, trouble breathing or urinary tract symptoms. 

What to Do If Your Dog Ate a Large Number of Probiotics

If your dog has ingested more probiotics than recommended, you need to contact your veterinarian. Take the package (or what’s left of it) with you to the vet clinic. It will be helpful for the doctor to know what and how much the dog ate.

If the dog is already showing symptoms like vomiting or diarrhea, your vet can help by administering supportive care. Your pup may need to stay in the vet hospital for IV fluids and anti-nausea medication until their body can recover. 

How to Give Probiotics to Dogs Safely

If you decide to try giving your dog probiotic supplements, take it seriously. Think twice before purchasing probiotic products marketed by random pet supply companies. At best, they will have zero effect on your dog but at worst, they might contain organisms or amounts differing from what’s on the label. 

Ask your vet for a recommendation on which dog probiotic to use for your unique dog. Most U.S. veterinary clinics stock Purina Pro Plan Fortiflora and Proviable DC. These are made by reputable companies with a long track record of manufacturing safe pet products. 

Make sure you follow the dosing instructions given by your vet (or on the product label). Giving less might not be therapeutic and giving more could make your pet sick.


While it is possible for a dog to overdose on probiotics, it is generally a rare occurrence when probiotics are used as directed. The most common dosing range is between 100 million to 100 billion colony-forming units of good bacteria and other microorganisms per dose. The maximum safe dose of probiotics a dog can tolerate is unknown.

The most common symptoms of probiotic overdose in dogs include diarrhea, gassiness, vomiting and decreased appetite. Factors that may increase the risk of probiotic overdose in dogs include underlying health conditions and compromised immune systems. 

Treatment for probiotic overdose in dogs by a veterinarian may involve supportive care, such as IV fluids and anti-nausea medications. To prevent probiotic overdose in dogs, use a dog-specific product, consult your vet before starting and keep the supplement locked in a safe place away from your dog.

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  1. Dore, M. P., Bibbò, S., Fresi, G., Bassotti, G., & Pes, G. M. (2019). Side effects associated with probiotic use in adult patients with inflammatory bowel disease: a systematic review and meta-analysis of randomized controlled trials. Nutrients, 11(12), 2913.
  2. Jensen, A. P., & Bjørnvad, C. R. (2019). Clinical effect of probiotics in prevention or treatment of gastrointestinal disease in dogs: a systematic review. Journal of veterinary internal medicine, 33(5), 1849-1864.
  3. Jugan, M. C., Wouda, R. M., & Higginbotham, M. L. (2021). Preliminary evaluation of probiotic effects on gastrointestinal signs in dogs with multicentric lymphoma undergoing multi‐agent chemotherapy: A randomised, placebo‐controlled study. Veterinary record open, 8(1), e2.
  4. Kochan, P., Chmielarczyk, A., Szymaniak, L., Brykczynski, M., Galant, K., Zych, A., … & Heczko, P. B. (2011). Lactobacillus rhamnosus administration causes sepsis in a cardiosurgical patient—is the time right to revise probiotic safety guidelines?. Clinical Microbiology and Infection, 17(10), 1589-1592.
  5. Land, M. H., Rouster-Stevens, K., Woods, C. R., Cannon, M. L., Cnota, J., & Shetty, A. K. (2005). Lactobacillus sepsis associated with probiotic therapy. Pediatrics, 115(1), 178-181.
    Salminen, M. K., Rautelin, H., Tynkkynen, S., Poussa, T., Saxelin, M., Valtonen, V., & Järvinen, A. (2004). Lactobacillus bacteremia, clinical significance, and patient outcome, with special focus on probiotic L. rhamnosus GG. Clinical infectious diseases, 38(1), 62-69.