A dog with diarrhea has almost always raided the bin, had its kibble changed too quickly, been through a stressful day or picked up worms, and it clears in a day or two with water and small bland meals. But diarrhea is also the first sign of serious diseases, including parvovirus in puppies, and a dehydrated dog goes downhill fast. Here is what you can do at home, what you must never give, what the look of the stool tells you, and the signs that mean the vet the same day.
Dog diarrhea: the key points
| The same day | a lot of blood or black stools, repeated vomiting, a lethargic or painful dog, an unvaccinated puppy, an old or ill dog, suspected poisoning, it cannot keep water down |
|---|---|
| Within 48 hours | the diarrhea lasts more than two days, it comes back every week, the dog is losing weight, a little red blood but the dog is bright |
| At home | bright dog that drinks and eats: water at will, digestive rest of 12 to 24 h at most (never for a puppy), then rice and chicken in small meals, gradual return to its kibble |
| Never give | any human anti-diarrheal without advice: loperamide (Imodium) is toxic to dogs carrying the MDR1 mutation (collies, Australian shepherds…) |
| Common causes | dietary indiscretion, food change, stress, parasites; more rarely infection, foreign body, poisoning, underlying disease |
| Puppies | diarrhea + vomiting + lethargy in an unvaccinated puppy aged 6 weeks to 6 months: parvovirus until proven otherwise, emergency |
| For the vet | a fresh stool sample, the list of what it ate, the dates of worming and vaccines |
Sources: Cornell Riney Canine Health Center, MSD Veterinary Manual, Washington State University (MDR1 mutation), ESCCAP, Frégis veterinary hospital. Details at the end of the article.
Contents
Why does my dog have diarrhea?
Cornell's Riney Canine Health Center separates two families of causes. The transient causes, by far the most common: dietary indiscretion (the bin, fatty leftovers, something dead found on a walk, too many treats), a food change made too quickly, stress (boarding, a vet visit, a move, fireworks) and intestinal parasites. And the serious causes: a digestive infection, viral such as parvovirus or bacterial, a foreign body blocking or irritating the gut, a food allergy or intolerance, poisoning, pancreatitis, liver, heart or adrenal disease (Addison's disease), inflammatory bowel disease or a tumour.
The difference is not read in the stool but in the dog: a dog with diarrhea that eats, drinks, plays and asks for its walk almost always has a transient cause. A dog that is lethargic, vomiting, refusing water or has a sore belly does not. That is the whole point of the next two sections.
What the look of the stool tells you
| Stool | What it suggests | What to do |
|---|---|---|
| Soft to liquid, brown | fast transit: dietary indiscretion, stress, food change | bland diet and watch for 48 hours if the dog is bright |
| Yellow or orange, sometimes green | transit so fast that bile has not had time to be processed; green also after eating grass | same; vet if it lasts or if the dog vomits |
| With mucus, small frequent amounts, straining | irritated colon (colitis): stress, indiscretion, parasites including Giardia | appointment if more than two days, with a stool sample |
| Streaks of bright red blood | bleeding from the colon or rectum: colitis, parasites, straining | a little blood in a bright dog: appointment within 24 to 48 h; a lot of blood, or a lethargic dog: the same day |
| Black, tarry, shiny | digested blood from the stomach or small intestine (melena): ulcer, foreign body, poisoning, tumour | the same day |
| Dark red, "raspberry jam", with vomiting | hemorrhagic gastroenteritis, especially in small dogs | emergency |
| Grey, greasy, bulky, dog losing weight | poor digestion or absorption: pancreas, intestine | appointment, work-up |
| Pure water, very strong smell, puppy | possible parvovirus | emergency |
Based on the Cornell Riney Canine Health Center (black stool: partially digested blood; foreign bodies, infections, inflammation, trauma, tumours, ulcers) and the MSD Veterinary Manual. Photograph the stool before picking it up: the vet prefers a photo to a description.
When to worry: the same day, within 48 hours, or at home
The vet the same day
- A lot of blood, or black stools like tar.
- Vomiting on top of the diarrhea, especially repeated: the dog is losing water at both ends, and Cornell notes that vomiting "further accelerates dehydration".
- A lethargic dog that will not get up, that trembles, with a tense or painful belly, or that stands hunched: abdominal pain can mean a blockage, which "requires emergency treatment", writes the MSD Veterinary Manual.
- It cannot keep water down or refuses to drink.
- A puppy, especially unvaccinated or mid-course, an old dog or one already ill (kidneys, heart, diabetes): they dehydrate within hours.
- Suspected poisoning: chocolate, grapes, medicines, rat poison, plants, party leftovers. Call your vet or an animal poison centre, and see the chocolate doses by weight in our guide Christmas with a dog or a cat.
- Very liquid, abundant diarrhea, more than three or four times in the day, in a small dog: the volume lost matters more than the cause.
An appointment within 48 hours
- The diarrhea lasts more than two days despite the diet: "if loose stool lasts more than two days, call the vet", sums up Cornell, and a bland diet that has changed nothing in two or three days warrants the visit.
- It comes back regularly, every week or at every change of routine.
- A little red blood or mucus, in a dog that is otherwise bright.
- It is losing weight, its coat is dull, its appetite is down.
- It has not been wormed for a long time, or lives in a group (boarding, kennel, shelter).
Watching at home
A bright adult dog that drinks, eats or accepts its bland diet, whose stools are soft or liquid but without blood, for less than 48 hours: you can manage, while watching closely. At the first sign from the first list, you change your mind.
Recognising dehydration
Dehydration is what turns a banal diarrhea into an emergency. Cornell is blunt: dehydration upsets the electrolytes, strains the kidneys and "can lead to organ failure and death". The signs to check twice a day: dry, tacky gums instead of moist and slippery ones, eyes that look sunken, a listless dog, and the skin tent: gently pinch the skin between the shoulder blades and let go; in a hydrated dog it snaps back at once, in a dehydrated dog it stays tented for a second or two. The test is less reliable in a puppy, a very thin or very old dog: when in doubt, the vet gives fluids.
What to do at home: the bland diet in three steps
For simple diarrhea in a healthy adult dog, the vets' protocol has not changed for years, with one exception: we no longer fast dogs for long.
- The first hours: water, and a short digestive rest. Fresh water available at all times, in small amounts often rather than a big bowl gulped down in one go. Cornell suggests withholding food for 12 to 24 hours in adults before moving to a bland diet; the MSD Manual notes that current thinking favours feeding earlier, and that "it was previously thought that food and water should be withheld until vomiting has subsided": that is no longer the case, and water is never withheld. Never fast a puppy, a toy dog, a diabetic or an old dog: they become hypoglycaemic.
- Days 1 and 2: small bland meals, often. "Mild cases of diarrhea in both cats and dogs can be treated at home by feeding a bland diet", writes Cornell: well-cooked white rice (almost overcooked, with its water) and boiled chicken or turkey, no skin or fat, or lean minced beef with the fat drained, or pasta, or a gastrointestinal diet prescribed by your vet. One third meat to two thirds rice, in four to six small meals a day, about the volume of its usual ration. No milk, no leftovers, no treats.
- Days 3 to 5: back to its kibble, gradually. As soon as the stools firm up, mix: a quarter kibble to three quarters bland diet, then half and half, then three quarters, over three to five days. Cornell warns that bland diets "are not appropriate for long-term feeding": they are unbalanced, you do not stay on them. If the diarrhea returns when the kibble is reintroduced, the vet will look for an intolerance.
Three extras everyone agrees on: take it out more often, it cannot hold on and scolding will change nothing; if you had changed its kibble in the preceding days, go back to the old food until the stools are firm then switch over one to two weeks, advises Cornell; and keep a stool sample (or a photo) for the vet if you have to consult. Probiotics for dogs can help some dogs get back to normal stools a little sooner; ask your vet which ones, human yoghurts and supplements have no place here.
What not to give
No human anti-diarrheal without your vet's advice. Cornell is explicit: do not give Pepto-Bismol or Imodium "unless a veterinarian directs it", because they "can be harmful to certain dogs and may not pair well with other medications". The case of loperamide (Imodium) deserves to be known by every owner of a herding dog: in dogs carrying the MDR1 mutation, which lets certain drugs into the brain, "at doses used to treat diarrhea, this drug will cause neurological toxicity", writes the reference laboratory at Washington State University, which asks that it be avoided in all carrier dogs. And the mutation affects about three collies in four, half of Australian shepherds and long-haired whippets, 15% of Shetland sheepdogs, 10% of German shepherds, and 5% of mixed-breed dogs, whose owners do not know. A genetic test exists; in the meantime, treat every herding dog as a carrier.
No human anti-inflammatories either (ibuprofen, paracetamol: toxic to dogs), no antibiotics from the cupboard: most diarrhea is viral, dietary or parasitic, and the MSD reminds us that antibiotics are added only "where secondary bacterial infection is likely to be present", which is decided in the consulting room. Clay-based intestinal adsorbents exist in veterinary versions: again, your vet says which one and how much.
Puppy diarrhea: the three causes to rule out
With a puppy, you do not wait and see: it weighs little, has no reserves, and dehydrates within hours. Three causes dominate.
Parvovirus
This is the absolute emergency of puppyhood. The MSD Veterinary Manual describes it: it mostly affects unvaccinated or incompletely vaccinated puppies aged 6 weeks to 6 months; signs appear 5 to 7 days after infection (2 to 14 days), vague at first, lethargy, loss of appetite, fever, then vomiting and hemorrhagic diarrhea within 24 to 48 hours. The virus spreads through faeces, directly or via shoes, hands and bowls, and it persists for at least two months indoors and many months outdoors. With intensive care (fluids, hospitalisation), 70 to 90% of puppies survive; without care, most die. The protection is the vaccine: MSD cites injections at 6–8, 10–12 and 14–16 weeks, a booster a year later and then every three years, because the mother's antibodies can neutralise the first doses. Until the course is complete, no dog parks, no busy pavements, no contact with dogs of unknown status.
Worms
Almost all puppies are born with roundworms, passed on by their mother, and worms cause soft diarrhea, a bloated belly, a dull coat and sometimes vomited worms. ESCCAP, the European network of veterinary parasitologists, recommends worming puppies every two weeks from 2 weeks of age until two weeks after weaning, then monthly until 6 months, with the mother at the same time; in adults, at least four times a year, more for a dog that hunts, eats prey or lives with young children. A "just in case" wormer is no substitute for a stool test if the diarrhea lasts. And a dog with fleas swallows fleas while grooming, and with them the tapeworm: see our guide dog fleas.
Giardia
These microscopic parasites cause intermittent, pale, soft, often mucoid diarrhea in a puppy that keeps its appetite but does not gain weight. ESCCAP says they occur "commonly in densely populated environments such as kennels, pet shops and animal shelters": a puppy arriving from a breeder or a shelter with soft stools is the ideal candidate. Diagnosis is made on the stools; the first-line treatment recommended by ESCCAP is fenbendazole for at least three days, ideally five, prescribed by the vet, with two steps that prevent reinfection: washing the puppy's hindquarters with a chlorhexidine shampoo at the end of treatment, to remove the cysts stuck to the hair, and washing bedding at 60 °C, picking up stools at once, cleaning and drying. The risk of transmission to humans is "considered to be very low", ESCCAP adds, but you wash your hands.
Chronic diarrhea: when it lasts or keeps coming back
Diarrhea that lasts more than three weeks, or that keeps coming back, is no longer a "tummy bug": it is a disease to be found. The usual suspects are food intolerance or allergy (the vet proposes a strict six- to eight-week elimination diet, with no lapses at all), inflammatory bowel disease, parasites that slipped through the first tests, exocrine pancreatic insufficiency (greasy stools, a ravenous dog losing weight), and diseases outside the gut: liver, kidneys, adrenals. The work-up includes repeated stool tests, a blood test, sometimes an ultrasound or biopsies. This is not a situation where changing kibble brand every week helps: every change muddies the trail.
Avoiding the next time
- A stable diet, and any transition over one to two weeks, mixing gradually.
- No table scraps, especially fatty ones (the day-after-the-party pancreatitis is a classic), no cooked bones, bins closed and compost out of reach.
- Worming and vaccines up to date, and a stool test at the slightest doubt.
- On walks: clean water that you bring, rather than the puddles and ponds where Giardia and bacteria lurk; a dog that picks up everything on walks can wear a basket muzzle while it learns "leave it".
- A dog that gulps its food digests badly and vomits: a slow-feeder bowl or a snuffle mat slow the meal down.
- Stress: before boarding, a sitter or a trip, keep its kibble and its routine, and warn the carer that a soft stool on the first day is common.
- After diarrhea: pick up at once in the garden, parasites settle back in through the soil, and wash the bedding.
The essentials: our selection
Nothing here treats diarrhea: these are the things that help you get through it, at home and on walks, and avoid the next one.
Washable pee padView product
Water bottle with folding bowlView product
Poop bags, 150 or 300View product
Slow-feeder bowlView product
Snuffle matView product
Microfibre towel 60 x 100 cmView product
Frequently asked questions about dog diarrhea
What should I feed a dog with diarrhea?
Very well-cooked white rice with boiled skinless chicken or turkey, one third meat to two thirds rice, in four to six small meals a day, for two days, then a gradual return to its kibble over three to five days. Never milk or leftovers.
Should I fast a dog with diarrhea?
At most 12 to 24 hours in a healthy adult, and never without water. Vets now refeed earlier and earlier. Never fast a puppy, a toy dog, a diabetic or an old dog.
How long does diarrhea last in dogs?
Banal diarrhea clears in 24 to 48 hours with the bland diet. Beyond two days without improvement, or if it keeps coming back, you need to consult with a stool sample.
When should I worry about diarrhea in my dog?
The same day if there is a lot of blood or black stools, vomiting, a lethargic or painful dog, an unvaccinated puppy, an old or ill dog, suspected poisoning, or if it cannot keep water down.
My dog has diarrhea with blood: is it serious?
A few streaks of bright red blood in a bright dog often come from an irritated colon: appointment within 24 to 48 hours. A lot of blood, dark red or tar-black stools, or a lethargic dog: emergency.
My dog has yellow diarrhea: why?
The transit is so fast that bile has not been processed: dietary indiscretion, stress, parasites. Bland diet and watch if the dog is bright; vet if it lasts more than two days or if it vomits.
My dog has diarrhea and is vomiting: what should I do?
See the vet the same day. Losing water at both ends dehydrates quickly, and vomiting plus diarrhea is the pattern of blockages, poisoning, hemorrhagic gastroenteritis and parvovirus.
How do I know if my dog is dehydrated?
Dry, tacky gums, sunken eyes, a listless dog, and a skin tent that stays up for a second or two when you pinch the skin between the shoulder blades. A dehydrated dog needs fluids: vet.
Can I give my dog Imodium?
Not without veterinary advice. Loperamide causes neurological toxicity in dogs carrying the MDR1 mutation: three collies in four, half of Australian shepherds, and 5% of mixed-breed dogs whose owners do not know.
Can I give my dog a clay-based anti-diarrheal?
Clay-based intestinal adsorbents exist in veterinary versions, dosed for dogs: ask your vet which one and how much. No human medicine is given on your own initiative.
My puppy has diarrhea: what should I do?
Consult without delay, especially if it vomits, is lethargic or is not fully vaccinated: parvovirus starts this way and kills without care. No fasting for a puppy. Worms and Giardia are the other causes to rule out.
Can a food change cause diarrhea?
Yes, it is one of the most common causes. Go back to the old food until the stools are firm, then switch over one to two weeks, mixing gradually.
Can stress give a dog diarrhea?
Yes: boarding, a move, a vet visit, fireworks or a newcomer often cause stress colitis, with mucoid stools and straining. It clears in a day or two with calm and the bland diet.
My dog has diarrhea but seems fine: should I see the vet?
Not right away: water at will, rice and chicken diet, watch closely. Consult if it lasts more than two days, if there is blood, if it vomits, if it refuses to drink or becomes lethargic.
Should I worm a dog with diarrhea?
If the last wormer was a while ago, yes, but a stool test beats blind treatment when the diarrhea lasts: not all parasites respond to the same product, Giardia for instance.
What should I bring to the vet?
A fresh stool sample in a clean pot, or at least a photo, the list of what it ate or may have swallowed, the date of the last wormer and the vaccination record.
Sources
- Cornell Riney Canine Health Center, "Diarrhea"
- MSD Veterinary Manual, disorders of the stomach and intestines in dogs and canine parvovirus
- Washington State University, WADDL laboratory, MDR1 in dogs
- ESCCAP, fact sheet "Giardia infection in dogs and cats" and guideline GL1 on worm control in dogs and cats
- Frégis veterinary hospital, emergencies: "Mon chien vomit" (in French)
Article updated on 15 October 2026. This article is no substitute for a consultation: a dog that vomits, bleeds or is lethargic, or a puppy, should be examined the same day. The photos in this article were generated by AI. Read also: Christmas with a dog or a cat: the dangerous foods, dog ticks and cat vomiting.
