If your dog is suffering from diarrhea it can be a frustrating time. It can be hard to work out what could have triggered the episode and also what you can do to help your pet feel better. Diarrhea can be messy and difficult to deal with at home too, especially if your pet is having accidents in the house.

This article gives some of the more common causes of diarrhea as well as some practical tips to help.

Reasons your dog has an upset stomach


There are many different causes of diarrhea in dogs, so it is not always possible to identify what the trigger is without seeking veterinary advice. In this section, we will explore some of the most common reasons your dog might have diarrhea.

1. Dietary indiscretion

This means eating something that he shouldn’t have done, especially if it’s gone bad. Dogs will frequently do this when out on walks, so it can be hard to avoid but discourage this behavior where possible. Feeding your dog table scraps and changing their normal diet suddenly could create tummy upset too.

2. Parasites

Large amounts of worms in your dog’s digestive tract could cause diarrhea. Other parasites such as the microscopic protozoan Giardia may cause loose stools and can be infectious between pets.

3. Bacterial

Salmonella, campylobacter, and E. coli can cause diarrhea in some animals. Eating uncooked meat puts dogs at higher risk of these infections, including animals that are on raw food diets.

4. Viral

Some viruses can cause diarrhea. The most well-known is parvovirus, which causes large amounts of bloody diarrhea and can be fatal. You can protect your dog against disease by getting him regularly vaccinated.

5. Food sensitivities

Some dogs with underlying food sensitivities or allergies may have upset stomachs. Doing a dietary trial under veterinary supervision can help diagnose this.


6. Inflammatory bowel disease (IBD)

This condition can have differing degrees of severity and associated causes. Some animals can be managed on hypoallergenic diets, whereas others may require medication.

7. Pancreatitis

This condition describes inflammation of a small organ known as the pancreas, which is responsible for the normal digestion of fats. When this happens dogs can suffer from a painful abdomen, vomiting, and diarrhea. They can become very lethargic and dehydrated.

Sometimes pancreatitis can be triggered by eating something very fatty or rich, and some breeds can be more prone to it than others, like miniature schnauzers and cocker spaniels.

8. Exocrine pancreatic insufficiency (EPI)

EPI is a condition whereby the pancreas doesn’t produce enough enzymes to help with the digestion of fats. This condition causes chronic diarrhea, and animals can suffer from severe malnutrition if left untreated.

9. Hemorrhagic gastroenteritis (HGE)

Also known as Acute Hemorrhagic Diarrhea Syndrome (AHDS), this condition presents as a sudden onset of bloody diarrhea, often with vomiting. Animals can become very unwell and require hospitalization for treatment. The exact cause is unknown but could possibly be triggered by allergies, parasites, or issues with blood clotting.

10. Addison’s disease

Otherwise known as hypoadrenocorticism, this condition is caused by the adrenal glands not producing enough hormones, including cortisol. These hormones help regulate electrolytes in the body as well as helping animals deal with stressful events.

Animals can show symptoms that wax and wane, and the condition may not be diagnosed until they have a serious Addisonian crisis, where they can present collapsed and extremely unwell. Diagnosis is made with blood samples and the condition will require lifelong treatment.

11. Cancer

Certain types of cancer could cause diarrhea in dogs. Tumors can cause loose stools with or without blood in them. The diagnosis will be made with a combination of blood tests, diagnostic imaging, and biopsies.

One-off occurrence vs. long-term condition


In most cases, dogs will have a short self-limiting bout of diarrhea which they recover from without too much intervention. This is a bit like us—we often have upset stomachs without requiring medical assistance, though we might feel a bit off-color at the time.

Some dogs can go on to have repeated bouts of diarrhea though or may be suffering from loose stools most days. This would be considered a long-term condition and requires investigation. Left untreated, your pet could become more poorly as well as suffering from issues like weight loss or weakness.

How to treat an upset stomach

If it is just a one-off episode of diarrhea and your dog is otherwise bright and well, then you could try treating him at home. You should offer your dog small amounts of bland easy-to-digest food at a time, such as cooked chicken breast, cooked white fish, and boiled white rice. Alternatively, you could get some sensitive stomach food over the counter from your veterinarian or your pet store.

Probiotics are another thing that you could try alongside bland food. The idea is to improve your dog’s gut flora and get some good bacteria back inside him. Some of these products contain things such as kaolin and montmorillonite, which help firm your dog’s stools up.

These products don’t require a prescription, so again can be purchased over the counter or online.

When to take your dog to the vet


There are occasions when your dog will require veterinary treatment. The following is a list of warning signs to look out for:

Blood in the stools

This can be fresh red blood, or black sticky digested blood (melena).

Large amounts of very watery stools

If your dog is passing frequent and copious amounts of very watery feces he is at risk of dehydration.


If he is vomiting as well as passing diarrhea then you should call your veterinarian for advice. See our link here for more information on vomiting in dogs.

Abdominal pain

Signs your dog may have pain in his tummy would include whimpering, crying when his tummy is touched, looking at his abdomen, holding himself in unusual postures to try and get comfortable, and bloating.


If your dog is not his normal self and seems quiet, you should get him checked out by a veterinarian, in case there is something more serious going on.


If your dog becomes weak or collapses you must see your veterinarian immediately. Your dog could be severely dehydrated or suffering from a serious underlying health complaint.

How your vet is likely to assess/treat your dog


Examination and possible blood test

Your veterinarian will start by examining your pet to look for signs of dehydration, abdominal pain, or a fever. Depending on the findings of their examination they might advise a blood test. A general health screen will further identify dehydration and assess any electrolyte imbalances.

More specific blood tests can look at your dog’s pancreatic enzymes to look for pancreatitis or an underactive pancreas (pancreatic insufficiency). Blood tests can also check your dog’s protein and vitamin levels as sometimes these can be deficient.

Fecal samples are often useful to look for infectious causes of diarrhea such as bacterial infections or parasites. Feces can also be assessed for signs of blood loss.

Diagnostic imaging (such as x-rays)

In some instances, diagnostic imaging is required, like x-rays or ultrasound scans. This will help to look for possible obstructions in your dog’s digestive tract as well as looking for signs of cancer, or liver issues. Surgical biopsies of your dog’s digestive tract are sometimes required for a definitive diagnosis for some more serious causes of diarrhea.

Food trials

Food trials are also a useful way of trying to work out if your dog has a food allergy or intolerance. Usually, your dog will be put on a very strict single-source diet for 6-8 weeks (with no other food, treats, tidbits, etc). If his diarrhea has resolved in that time then the diet is challenged with different foods (like chicken or beef), to see if he reacts and has diarrhea again—your veterinarian will be able to advise you on this further.

How to prevent your dog from getting an upset stomach


While it is impossible to stop your dog from getting upset stomachs altogether, there are some sensible steps you can take to help.

  • Don’t feed your dog table scraps, especially ones that are rich or fatty,
  • Don’t suddenly change your dog’s diet, do this gradually, mixing the new food with the old over several days,
  • Discourage your dog from scavenging while out on walks,
  • Keep up to date with preventative parasite control, to stop heavy worm burdens,
  • Ensure your dog is vaccinated to prevent viral causes of diarrhea,
  • Regular check-ups with your veterinarian to pick up any underlying health problems early.


There are many different reasons your dog might have diarrhea, so always get veterinary advice if you are worried, especially if your dog is showing any of the warning signs we discussed earlier. Mild cases can be self-limiting, so if your dog is otherwise bright and well in itself, it may resolve with a bit of bland food. But if things aren’t getting better, then you should always seek help in case there is something more serious going on.