Dog Diarrhoea: Causes, Treatment and When to See a Vet

Few things send a pet parent into worry mode faster than spotting a puddle of dog diarrhoea on the kitchen floor. If you've found yourself frantically Googling "why does my dog have runny poo?" at 6am, take a breath — you're not alone. Loose, messy stools are one of the most common reasons dogs end up at the vet, and most cases clear up on their own.

In this thorough guide, we'll explain what dog diarrhoea actually is, the many possible causes, how to tell benign upset from a real cause for concern, what you can safely do at home, and exactly when to see your veterinarian. By the end, you'll feel far calmer about reading your furry friend's poop — and far more confident about what to do next.

What Is Dog Diarrhoea?

Diarrhoea is simply loose, watery or more frequent poo than normal. It's a symptom of a disease or upset rather than an illness in itself — in other words, diarrhoea is not a disease, it's a sign that something in your dog's digestive system isn't happy.

When food moves through the gastrointestinal tract too quickly, or the intestines can't absorb water properly, the result is loose stools. It's your dog's body reacting to an irritant, an infection, or a change somewhere along the intestinal tract. Understanding the underlying cause is the key to helping your pup feel better.

Why Dogs Get Diarrhoea

Your dog's gut is a busy, sensitive place. From the small intestine that absorbs nutrients to the large intestine and colon that firm things up, a lot has to go right for a nice, solid poo. A wobble in the gut microbiome — the balance of good bacteria, or gut microflora — is often all it takes to cause a bout of digestive upset. That kind of mild digestive upset is exactly what leads to those messy puddles on the floor.

The good news is that many cases of diarrhoea in dogs are mild and self-limiting, meaning they settle within a day or two without any special treatment. But some cases point to a more serious underlying condition, so it always pays to know what to look for.

Common Causes of Diarrhoea in Dogs

There are dozens of reasons for diarrhoea in dogs, but they tend to fall into a handful of groups. We'll start with the most common and least worrying, then work towards the ones that need veterinary attention.

Dietary Indiscretion

This is a fancy vet term for "my dog ate something they shouldn't." Dietary indiscretion is far and away the most frequent cause of dog diarrhoea. Think raiding the bin, hoovering up table scraps, snaffling spoiled food on a walk, or scoffing something greasy.

• Eating garbage: rubbish and rotten food are full of bacteria that irritate the gut.
• Rich or fatty food: a sneaky sausage or leftover roast can overwhelm a dog's digestion — and fatty foods are a common trigger.
• Eating something they shouldn't: grass, sticks, socks and other non-food finds all cause tummy trouble. Your pup eating something they shouldn't is the number-one reason for a sudden bout of the runs.

Change in Diet

A sudden diet change is another classic culprit. When you introduce new food too fast, the gut microbiome doesn't have time to adjust. Switching foods too quickly — a sudden change in food without a gradual transition — often leads to soft stools for a few days. Even a change of treats can be enough to bring on soft stools in a dog with a sensitive stomach.

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Food Allergies and Intolerances

Some dogs have a genuine food allergy or food intolerance. A true food allergy involves the immune system, while food intolerances are simply an inability to digest an ingredient. Both are types of adverse food reactions and can cause chronic loose stools, flatulence and itchy skin. Dogs with a sensitive stomach are especially prone, and a persistent loose stool is often the first clue. Your vet may suggest an elimination diet to pinpoint the trigger.

Stress or Anxiety

Yes, dogs get "nervous tummy" too. Stress or anxiety floods the body with hormones that speed up the gut. Big life events cause a spike in stress and anxiety that can trigger a bout of colitis almost overnight.

• Fireworks and thunderstorms
• Boarding in kennels or a stay away from home
• Moving home or a new baby in the house

Infections

Both viral infections and bacterial infections can wreak havoc on the GI tract. A mild viral infection might pass quickly, but some are serious, and certain bacterial infections can pass to people too.

• Parvovirus: canine parvovirus (often just called parvo) is life-threatening, especially in unvaccinated puppies, and often causes bloody diarrhoea.
• Distemper and coronavirus: canine distemper and coronavirus are other viral causes.
• Bacterial infection: salmonella, campylobacter and clostridium commonly come from raw or contaminated food, with salmonella being a well-known risk of raw feeding.

Intestinal Parasites and Worms

Intestinal parasites are a very common cause of diarrhoea in dogs, particularly in puppies. Various worms and single-celled protozoa irritate the gut lining and the walls of the intestines.

• Roundworms, hookworms and whipworms are the usual suspects, along with tapeworms.
• Roundworms are especially common in puppies, while hookworms and whipworms tend to affect dogs that spend a lot of time outdoors.
• Giardia and coccidia are microscopic parasites that thrive in damp, communal spaces.

Regular worming prevention keeps most of these at bay, which is why routine treatment matters so much.

Toxins and Poisons

Toxin ingestion is always a red flag. Many everyday items are toxins or poisons to dogs.

• Chocolate and raisins: even small amounts of chocolate can be dangerous.
• Poisonous plants in the garden.
• Household chemicals like antifreeze and cleaning products.

Foreign Body or Blockage

Dogs love to swallow things they shouldn't. A foreign body — a sock, a toy, a stone — can cause a partial intestinal blockage. Foreign body ingestion can start as diarrhoea but quickly become a surgical emergency. If a foreign object causes a full obstruction or gut blockage, your dog will usually vomit, stop eating and show signs of pain. A blockage is one of the reasons any diarrhoea with repeated vomiting needs prompt veterinary care. Watch especially closely with small-breed dogs, whose narrow guts block more easily. Multiple foreign bodies are common in enthusiastic chewers.

Pancreatitis

Pancreatitis is inflammation of the pancreas, often triggered by rich or fatty food. When the pancreas becomes inflamed, dogs typically show vomiting, abdominal pain and diarrhoea together. It's painful and needs proper veterinary care.

Liver or Kidney Disease and Other Underlying Conditions

Longer-lasting cases may point to an underlying health condition, including:

• Inflammatory bowel disease (IBD) and colitis, which inflame the gastrointestinal tract. Inflammatory bowel disease tends to cause on-and-off symptoms over months.
• Exocrine pancreatic insufficiency (EPI), where the body can't produce enough digestive enzymes.
• Liver or kidney disease — both liver disease and advanced kidney failure can upset digestion and are serious.
• Cancer, including intestinal cancer, is a rarer but important cause.
• Haemorrhagic gastroenteritis (HGE), a sudden, severe gastroenteritis with bloody, jelly-like stools.

Medications

Some medications upset the gut as a side effect. Antibiotics can wipe out helpful bacteria in the GI tract, while NSAIDs and other anti-inflammatory drugs can irritate the stomach lining. If your dog develops diarrhoea while on a course of antibiotics, mention it to your vet. Recent vaccinations and worming treatments occasionally cause a brief, mild upset too.

Types of Diarrhoea in Dogs

Vets often classify diarrhoea by where in the gut it starts and how long it lasts. Knowing the type helps everyone work out the likely cause.

• Small bowel diarrhoea: large volumes of watery stools, usually less frequent, sometimes with weight loss.
• Large bowel diarrhoea: smaller amounts passed often, frequently with mucus, straining and increased urgency.
• Acute diarrhoea: comes on suddenly and often resolves within a couple of days.
• Chronic diarrhoea: lasts longer and points to an ongoing problem.

Acute Dog Diarrhoea and Feeding Tips

Acute diarrhoea is the sudden, short-lived kind — usually from dietary indiscretion or a passing bug. Most acute cases of acute diarrhoea are self-limiting and improve within 24 to 48 hours with simple home care and a gentle diet. In these cases you'll often notice sudden watery diarrhoea that firms up again within a day or two.

Chronic Diarrhoea in Dogs

Chronic diarrhoea is diarrhoea that lasts more than two weeks or keeps returning. Chronic diarrhoea is more likely to signal an underlying condition such as IBD, food allergies, parasites or EPI, and always deserves proper investigation by your vet.

Diarrhoea Symptoms in Dogs

Diarrhoea rarely arrives alone. Keep an eye out for these accompanying signs, as they help gauge how worried to be.

Watch closely for signs of dehydration — repeated vomiting and diarrhoea drain fluids fast. Dehydration shows up as dry gums, sunken eyes and skin that's slow to spring back. If you're worried your dog isn't drinking, our guide on how much water your dog should drink is a handy read.

Bloody Diarrhoea in Dogs

Bloody diarrhoea always raises the alarm. There are two types of blood in the stool to know about:

• Fresh (bright red) blood in stool: usually comes from the large intestine or colon and often appears with mucus.
• Tarry stools: black, sticky tarry stools or dark diarrhoea suggest digested blood from higher up the gut.

A little blood and mucus with a one-off large bowel diarrhoea episode is often mild colitis, and seeing some mucus in dog poop now and then isn't unusual. But heavy or repeated bloody diarrhoea — especially with vomiting — needs emergency care, as it can signal parvo, HGE or a foreign body.

What should dog poop look like?

Knowing what healthy dog poop looks like makes it much easier to spot trouble. Vets use a fecal scoring chart (or stool chart) to grade stool consistency from hard pellets to pure liquid.

Ideal dog poop is firm, log-shaped and holds its form when picked up. The colour should be a rich chocolate brown. When you inspect your dog's poop, watch for changes in colour, consistency or the appearance of watery diarrhea. Checking your dog's poop each day makes it easy to catch problems early. On the flip side, straining with hard, dry stools points to constipation rather than diarrhoea. Any lasting change in your dog's normal bowel movement is worth noting, and a change in the look or smell of every bowel movement can be an early warning sign. For more on this, see our post on how often your dog should poop.

When Is Dog Diarrhea Cause for Concern?

Most mild, one-off dog diarrhea isn't a cause for concern — but certain dogs and certain signs mean you shouldn't wait it out.

Be extra cautious with the very young or very old, and with any dog that has a compromised immune system. Puppies, especially unvaccinated puppies, can go downhill fast, and a puppy with watery diarrhoea should be seen promptly. Use these verdict pills as a rough guide: ✓ Mild, one-off, dog otherwise bright ⚠ Lasting over 48 hours ＋ Blood, collapse or a suspected toxin

When should you bring your dog to the vet?

You should see your veterinarian — and in some cases seek emergency care — if your dog has any of the following:

• Diarrhoea lasting more than 24 to 48 hours, or chronic diarrhea lasting more than two weeks
• Bloody diarrhea, blood in the stool, or tarry stools
• Repeated vomiting, fever, severe lethargy or a sudden loss of appetite
• Clear signs of dehydration like dry gums and sunken eyes
• Any suspected toxin ingestion or swallowed foreign object

How is the cause of diarrhea diagnosed?

When you contact your vet, they'll want to get to the underlying cause. Expect a mix of the following diagnostic tests:

1. History and examination

   Your vet will take a full medical history and perform a hands-on physical examination, feeling the tummy for pain or a possible blockage.

2. Stool sample testing

   Bringing a fresh stool sample speeds things up. A fecal exam or stool test checks a stool sample for roundworms, hookworms, whipworms, giardia, coccidia and bacterial infections such as salmonella.

3. Bloodwork and imaging

   Bloodwork can reveal pancreatitis, liver disease, kidney disease, inflammatory bowel disease and infection. X-rays help spot a foreign body or intestinal blockage.

4. A tailored treatment plan

   With the cause identified, your vet builds a treatment plan — which might include fluids, medications, antibiotics, deworming or a special diet.

What Should I Do If My Dog Has Diarrhoea?

For a bright, otherwise well adult dog with mild, acute diarrhea, there's plenty you can do at home. These simple home remedies support recovery while nature does its thing.

1. Consider a short fast

   For adult dogs, some vets suggest you briefly withhold food for a few hours to rest the gut — a gentle fasting period. Never fast puppies, tiny breeds or unwell dogs.

2. Keep them hydrated

   The most important step is to help your dog stay hydrated. Always offer plenty of fresh water, as diarrhoea and vomiting quickly lead to dehydration.

3. Feed a bland diet

   Reintroduce food with a gentle bland diet of rice and chicken — boiled chicken with boiled rice (plain white rice is easiest to digest). A little plain pumpkin adds soothing fibre, and this simple fiber for dogs trick can firm up soft stool. It's a kind, easily digested option for a dog with a sensitive stomach or a lingering soft stool.

4. Support the gut

   A dog-specific probiotic helps restore the gut microflora and settle the digestive upset. Once your dog is back to normal, transition to a highly digestible food or a low-fat diet if a sensitive tummy is the issue.

Cleaning up? An enzymatic cleaner breaks down odours and stains far better than ordinary sprays — a real lifesaver during a messy few days.

Quick questions

Remember, no one knows your dog like you do. Trust your instincts, keep an eye on their poo, and don't hesitate to seek veterinary care if something feels off. Here's to happy tummies and firm, chocolate brown poos! Loved this guide? Sign up to our newsletter for more, and share it with a fellow pet parent who could use the reassurance.

Sources & further reading

• Why Is My Dog Pooping in the House?
• How Often Should My Dog Poop?
• How Much Water Should My Dog Drink?