My Dog Has Diarrhea: Most Common Causes of Dog Diarrhea

We don’t talk about it much, but dog owners spend a lot of time scrutinizing their pets’ stools. There are all kinds of information in it about animal health, diet, and potential parasites. So, when you realize your dog has diarrhea, asking why is only natural. 

Here are some of the most common causes of dog diarrhea and ways to address the problem. 

But first, what does healthy dog poop look like? 

How Can I Tell My Dog Has Diarrhea? 

Healthy stool plays a significant role in maintaining your dog’s health. Soft poo, especially, doesn’t put adequate pressure on your dog’s anal sack, and that stops the glands from expressing. 

Full anal glands cause discomfort for your dog and in worst-case scenarios, may create abscesses and require surgery. No wonder dog owners pay so much attention to doggy poo. 

Ideally, your dog’s poo should be approximately the consistency of soft-scoop ice cream. It’s firm enough to express the anal glands but not so hard that your dog has to strain. It keeps its shape, and you can pick it up easily. 

It’s diarrhoeic when it loses shape when picked up or has no shape and is a soupy consistency.

Reasons My Dog Has Diarrhea

If you are wondering “Why does my dog have diarrhea,” there are many possible causes. Here are the most common. 


Anxiety may not seem like the obvious answer when you call the vet to report that your dog has diarrhea

But there’s a connection between your dog’s brain and their gut. When stressed or anxious, the brain increases norepinephrine. That’s the hormone behind your dog’s fight or flight instinct. Dogs that favor flight may respond to stressful scenarios by experiencing diarrhea. 

Canine anxiety has various causes and often dovetails with significant changes in your dog’s life, like:

  • New family members 
  • Loss of family member 
  • Moving house 

Eating Spoiled Food 

Dogs are notorious for eating things they shouldn’t. Their keen noses make them as interested in dried chewing gum as in scraps from the dinner table. 

If you realize your dog has diarrhea and has been eating things they shouldn’t, this may be the cause. 

Spoiled food can trigger mild bouts of food poisoning, and this sometimes presents with diarrhea as a symptom. Other symptoms include: 

  • Vomiting 
  • Lethargy
  • Loss of appetite  

Typically, this type of diarrhea resolves without a trip to the emergency vet. But depending on what your dog ate, the symptoms may persist longer than usual. In that case, speaking to a vet about medication to alleviate the symptoms may help. 

Sudden Change in Diet 

Sometimes canine diarrhea happens because you changed your dog’s pet food suddenly. 

The shock of the switch surprises your dog’s digestive tract, and it responds by producing softer-than-normal poo. 

For that reason, vets encourage owners to switch foods gradually. Ideally, you want to mix the new food in with the old, starting at a ratio of 10% new to 90% old. As your dog acclimatizes, you decrease the percentage of old food until they eat exclusively from the new diet.

There are some fruits and vegetables that you can give your dog to help with an upset stomach and diarrhea. Many people will give their dogs strawberries or pumpkins to help relief their upset stomach because of the fiber and vitamins within them.

Underlying Illness 

Various illnesses can cause diarrhea, as part of your dog’s immune response when fighting them off. These range from the parasitic and include round- and hookworms, to the viral, like Giardia or parvovirus. 

And, as discussed, bacterial infections like salmonella can also bring on diarrhea. 

Antibiotic Treatment 

Confusingly, sometimes you call the vet for one problem only to ring up several days later because your dog has diarrhea. 

It’s not unusual for certain antibiotics to cause diarrhea in dogs. This is a normal side-effect, and you will notice the problem shortly after administering the antibiotic. Typically, if the antibiotic affects your pet this way, it happens within the first day or two. 

If it doesn’t clear up, your vet may change your dog’s prescription or add medication to relieve diarrhea. 

How to Treat My Dog’s Diarrhea 

First, here’s what not to do. Even if you are concerned your dog has diarrhea, never give them human medication for it. 

Some human medicines can work on dogs, but you should only administer them with a vet’s recommendation. Guessing the correct dosage for your pet’s weight is challenging and should be left to experts.

It’s also important to remember that diarrhea often resolves on its own. If you notice some after dinner and your dog’s poo is normal by breakfast, there’s no need to worry. 

If diarrhea becomes chronic and lasts more than 48 hours, it’s time to call the vet. Keep in mind that depending on the diagnosis, treatment will vary. A stressed dog may benefit from synthetic pheromone dispensers, while a dog suddenly transitioning to new food does better when you mix some of their old food back into their meal. 

When It’s Not Diarrhea 

Sometimes, what looks like diarrhea is constipation. Many people look at small amounts of liquid stool and naturally assume it’s diarrhea. 

However, when dogs become constipated, sometimes a few liquid drops of poo are all they can get out. So, how do you tell the difference? 

The primary indicator of a constipated dog is straining. Diarrhea never results in difficult bowel movements. If your dog spends several seconds or minutes straining and only manages a bit of liquid poo, it probably isn’t diarrhea. 

It’s still treatable, but the conversation you need to have with the vet is different. 


Before calling the vet to let them know your dog has diarrhea, it’s important to remember that this problem often resolves on its own. This is especially true if your dog reacts adversely to something they should never have eaten in the first place. 

However, if your dog shows signs of chronic diarrhea, it’s time to call the vet. It could point to an underlying infection or parasite. Or it might be brought on by stress. Whatever the cause, dog diarrhea is easily treated. 

But remember, leave the diagnosing to others. Human medication is best-suited to people, and giving it to your dog could exacerbate the problem. 

Ultimately, you know your dog best. If they exhibit diarrhea or seem different to you, don’t hesitate to call a vet and ask for help.

Photo of author

Dr. Jacob Hawthorne, DVM

Dr. Jacob Hawthorne, DVM is a certified veterinarian who graduated from the University of California - Davis Veterinary School in 2012. He specializes in nutrition and veterinary medicine for companion animals such as dogs, cats, rabbits, and more. He has been featured in websites such as PetMD, Yahoo News, Hills Pet, Daily Paws, and more. Learn more about Dr. Jacob Hawthorne, DVM.

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