Dog diarrhoea: when to watch at home and when to go

Quick answer

Most dogs get diarrhoea at some point and most cases resolve. The decision that matters is not what to feed but whether this dog can safely be watched at home, and that is answered by the dog rather than by the stool.

A bright, drinking, comfortable adult dog with soft stool and no other signs can usually be observed. A dog that is flat, vomiting repeatedly, passing black or heavily bloodstained stool, or under six months old and not fully vaccinated cannot.

How the dog looks between trips outside carries more information than the stool itself.

• Learn the difference between small bowel and large bowel diarrhoea. It narrows the causes more than anything else you can observe.
• Black, tarry stool means digested blood from higher up the tract. It is a same day sign, not a wait and see sign.
• Prolonged fasting is outdated advice. Early, small, easily digested meals are now preferred for most cases.
• Never give human anti-diarrhoeal medicines. Loperamide is dangerous in herding breeds carrying the MDR1 mutation.
• A puppy with diarrhoea is a different animal from an adult with diarrhoea, and the threshold for being seen is much lower.

:::danger
Go to a vet immediately, out of hours if necessary, for any of the following.

Black tarry stool, a large volume of fresh blood, pale or white gums, collapse or an inability to stand, repeated unproductive retching with a swelling or tightening abdomen, a puppy under six months with diarrhoea and vomiting, a dog with known access to a toxin, or a dog that has swallowed a foreign object.

Acute haemorrhagic diarrhoea syndrome, sometimes still called haemorrhagic gastroenteritis, produces sudden large volume bloody diarrhoea often described as looking like raspberry jam. Fluid moves out of the circulation into the gut so quickly that a previously well dog can go into shock within hours. It is treatable and it is time critical.

Unproductive retching with a distending abdomen is not a diarrhoea problem at all. It is the presentation of gastric dilatation and volvulus, which kills deep chested dogs within hours.
:::

Decide in 60 seconds

The single most useful distinction

Where the problem sits in the intestine changes the list of likely causes, and you can tell from the pattern without any equipment.

Small bowel pattern.

Larger than normal volumes, perhaps three or four trips a day rather than twenty. Often watery. Weight loss if it continues. Vomiting is common. Blood, if present, appears as black, tarry, sticky stool because it has been digested on the way through. Gas and gurgling are common.

Causes that sit here include dietary indiscretion, abrupt diet change, parvovirus, small intestinal parasites, pancreatitis, partial obstruction, exocrine pancreatic insufficiency, lymphangiectasia, inflammatory bowel disease and lymphoma.

Large bowel pattern.

Small amounts passed frequently, sometimes ten or more times a day. Urgency, straining after the stool has been passed, visible mucus like jelly, and fresh red streaks or spots of blood. The dog often seems otherwise well and keeps eating.

Causes that sit here include stress colitis after boarding or a change in routine, whipworm, dietary intolerance, clostridial overgrowth, and in Boxers and French bulldogs a specific ulcerative colitis.

Mixed pattern.

Both sets of features together suggests a diffuse process, and it takes the case out of the watch at home category.

What is actually causing it

Dietary indiscretion and abrupt diet change.

The most common cause by a wide margin. Bin raiding, a stolen fatty meal, a new treat, a change of food without transition, or a rich food given as a kindness. Usually self limiting.

Parasites.

Roundworms and hookworms matter most in puppies, whipworms produce a stubborn large bowel picture in adults, and giardia produces greasy, foul, intermittent diarrhoea that often defeats a single course of treatment. Worming history matters and most owners are less up to date than they think.

Infectious disease.

Parvovirus in unvaccinated dogs, especially puppies. Campylobacter and salmonella, both of which can affect people in the household. Leptospirosis, which is more common after flooding and in areas with rats and standing water.

Pancreatitis.

Often follows a fatty meal. Typically vomiting, a painful abdomen, a hunched or praying posture, and reluctance to eat. Miniature schnauzers, Yorkshire terriers and cocker spaniels are over represented.

Foreign body and partial obstruction.

Intermittent vomiting with diarrhoea, a dog that is off colour, and often a history of chewing toys, socks or corn cobs. Intussusception, where the bowel telescopes into itself, occurs in puppies with existing diarrhoea and turns a manageable case into a surgical one.

Addison's disease.

Hypoadrenocorticism produces episodes of vomiting, diarrhoea and lethargy that resolve and then return. It is frequently mistaken for repeated dietary upsets until the dog collapses. Standard poodles, bearded collies, Portuguese water dogs and West Highland white terriers are among the breeds over represented.

Chronic enteropathies.

Food responsive disease, antibiotic responsive disease and inflammatory bowel disease all produce recurring signs over weeks to months. German shepherd dogs are notably over represented, and so are several terrier breeds for protein losing forms.

Exocrine pancreatic insufficiency.

Large volume, pale, greasy stool in a dog that is ravenously hungry and losing weight, most classically in German shepherds. It looks like a feeding problem and it is a pancreatic one.

Neoplasia.

In older dogs, persistent or recurring diarrhoea with weight loss deserves investigation rather than another course of bland food.

Toxins and medications.

Non steroidal anti inflammatories, some antibiotics, and a long list of garden and household toxins. Always tell the vet everything the dog is on, including supplements.

The seasons and situations that change the odds

Spring and summer bring scavenging, compost heaps, barbecue leftovers, wildlife faeces, and blue green algae in warm standing water, which is rapidly fatal and produces vomiting and diarrhoea among its early signs.

Autumn brings mushrooms and acorns, and in some regions a rise in leptospirosis after wet weather.

Holidays bring fatty human food, bones, chocolate, raisins and sultanas in baking, and dogs left with unfamiliar sitters, which is also when stress colitis peaks.

Boarding, kennels, shows, moving house and the arrival of a baby all produce large bowel diarrhoea in otherwise healthy dogs, and it typically starts a day or two after the event rather than during it.

What to do at home when watching is reasonable

A written timeline and a weight are the two things that make the appointment productive if home management does not work.

Feed, do not starve.

The old advice to withhold food for twenty four hours has largely been abandoned. The intestinal lining is fuelled directly from the gut contents, and prolonged fasting slows its repair. Small, frequent, low fat, highly digestible meals are preferred, and this is more important, not less, in puppies and small breeds where hypoglycaemia is a real risk.

A veterinary gastrointestinal diet is the cleanest option. A simple home alternative is boiled white rice or plain pasta with boiled skinless chicken or white fish, offered in small amounts several times a day, with nothing else at all. Return to the normal diet gradually over several days once stools firm up.

Keep water available.

Do not restrict water to reduce output. Dogs lose a great deal of fluid through diarrhoea and restricting intake is how a manageable case becomes a dehydrated one.

Keep a record.

Time and description of every stool, every vomit, what was eaten, and how the dog seems between episodes. This is the information a vet needs and it is impossible to reconstruct afterwards.

Weigh the dog.

A weight now, and one every day if this continues. Weight loss changes the urgency.

Check hydration crudely but usefully.

Gums should feel wet and slippery, not tacky. Press a finger on the gum and the colour should return in about a second. Skin tenting over the shoulders is a rough guide but is unreliable in old, thin or overweight dogs.

Separate from other dogs where practical, and pick up stools promptly. Wash hands after every clean up, and be strict about it if anyone in the household is pregnant, very young, elderly or immunosuppressed.

Where the popular advice fails

Human anti-diarrhoeal tablets.

Loperamide slows the gut, which is exactly wrong when the body is clearing an infection or a toxin, and it is dangerous in Collies, Australian shepherds, Shetland sheepdogs, Border collies and other herding breeds carrying the MDR1 mutation, in which it crosses into the brain and causes severe neurological signs. Bismuth containing human products contain a salicylate. None of these should be given without veterinary instruction.

Leftover antibiotics.

Most acute diarrhoea in dogs does not need antibiotics, and using them unnecessarily disrupts the gut flora further and drives resistance.

Long fasting.

Covered above. It delays recovery and risks hypoglycaemia in small and young dogs.

Assuming blood always means emergency, or never does.

A few streaks of fresh blood with mucus in a bright dog with colitis is common and usually not urgent. Black tarry stool in the same dog is urgent. The colour matters more than the presence.

Assuming a dog that keeps eating must be fine.

Dogs with obstructions, Addison's disease and early pancreatitis often still eat. Appetite is reassuring but it is not decisive.

Repeating the same bland diet cycle for months.

Diarrhoea that keeps returning is a diagnosis waiting to be made, not a diet to be repeated.

What the vet will want

General condition, coat quality and hydration tell a vet as much about a chronic gut problem as the stool does.

Bring a fresh stool sample if you can, collected from a clean surface rather than scraped off grass, sealed, and refrigerated if it will be more than a couple of hours. A photograph of the stool is genuinely useful and vets would rather see it than hear it described.

Bring the timeline: when it started, how many times a day, volume per episode, straining or not, mucus or not, blood and what colour.

Bring the diet history: what the dog normally eats, what changed, what it might have found, and every treat, chew and supplement.

Bring the medical facts: worming product and date, vaccination status and dates, current medications, travel history, and whether other dogs or people in the household are also unwell.

Bring the weight, and any earlier weights you have.

What never to do

Do not give human medications of any kind without instruction.

Do not withhold water.

Do not feed a fatty food to tempt an inappetent dog. Cheese, cooked meat trimmings and butter are how pancreatitis cases start.

Do not restart the normal diet at full quantity the moment one stool looks better.

Do not delay for a puppy. Parvovirus can go from mild signs to critical illness in under a day.

Do not use another dog's prescription food or medication.

Do not assume a dog that has had a stressful week has stress colitis without checking. Stress and disease coexist comfortably.

When to get help

Book the same day for blood in any form, repeated vomiting alongside diarrhoea, lethargy, a painful abdomen, a puppy or incompletely vaccinated dog, a senior dog, or any dog with an existing medical condition.

Go immediately for collapse, pale gums, black tarry stool, large volume bloody diarrhoea, or unproductive retching with a swelling abdomen.

Recovery is a dog back to its normal energy, weight and appetite, with formed stools that stay formed after the diet returns to normal.

Book a non urgent investigation appointment for diarrhoea that keeps returning, for stools that never quite firm up, and for any dog that is slowly losing weight or condition alongside intermittent gut signs. Those cases get answers from testing, not from another week of chicken and rice.