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This guide helps you triage; it does not replace your veterinarian's exam. When in doubt, call us at 514 223-1197.
Go now: the signs that cannot wait
Any single one of these is enough. Don't wait to "see if it passes", don't wait for morning: head to the clinic or the nearest emergency centre, and call on the way so they are ready for you.
- Significant blood in the stool, or watery diarrhea that looks like raspberry jam or jelly. This picture goes downhill fast, and it can do so before your dog looks dehydrated at all: "he's still drinking" and "he seems fine in between" prove nothing.
- Stools that are black, sticky and tarry: that is digested blood, coming from higher up in the gut. A stool that is darker than usual already deserves a call; a truly black one means now.
- He has diarrhea, he is vomiting, and he is flat: he gets up reluctantly, refuses water or brings it back up. He is emptying out faster than he can fill back up, and that cannot be fixed at home.
- His belly is tight, swollen or painful: he freezes, he paces, he stretches his front end to the floor as if bowing, he stiffens or growls when your hand comes near.
- He is very weak, staggering, or collapsing. Pale, grey or white gums confirm the emergency, but they are a late sign: do not wait to see them before leaving, and never use gum colour as a green light (early in shock they can stay pink, or even look redder than usual).
- A toxin is possible: rat poison, chocolate, cannabis, a human medication, garbage or mouldy compost, an unknown plant. Diarrhea is no longer the subject: leave now with the packaging, a photo of the label, or a twin of the product, and do not make him vomit on your own initiative.
- He may have swallowed an object (a toy, a ball, a bone, a corn cob, fabric, string). Diarrhea does not rule out something stuck: see section 3.
- He is a puppy, and there is blood, vomiting on top, or he is going flat and less responsive: in puppies, everything moves faster (section 7).
Chocolate, grapes, human medications, antifreeze, rat poison: our dedicated pages give the first steps for each product:
Diarrhea after exercise or a hot day
If the diarrhea follows exercise, a hot car or a heat wave, especially if there is blood in it, think heatstroke before you think gut. This is the one situation where you do not leave first: you cool first, then you drive. Our guide tells you exactly how, and in what order. Heatstroke: the first steps
Blood in the stool: two readings, neither of them harmless
This is probably what you are looking at right now, and it is the right thing to look at. Blood reads two different ways depending on where it comes from, and neither one is something you watch in silence.
Bright red
In streaks, in small amounts mixed through a soft stool, or as a puddle: the bleeding is more likely coming from the lower gut, closest to the exit. A few streaks on one stool, in a dog who is otherwise completely himself: call us today. Blood in quantity, or blood together with any single sign from the section above: leave now.
Black and tarry: melena
Stools that are black, sticky and shiny, sometimes like coffee grounds: the blood has been digested, so it comes from higher up. It is the sign most often missed at home, because a black stool first reads as simply a dark one. If you are unsure, take it out into daylight, photograph it, and call: never file black as less serious than red.
Watery, profuse and frankly bloody
Watery diarrhea that looks like jam or raspberry jelly, often in a small dog, sometimes preceded by vomiting earlier the same day: this picture deteriorates quickly. The fluid loss can tip a dog over before he ever looks dehydrated. Do not wait until you have every sign at once to make up your mind.
Two things that blur the reading
Pepto-Bismol and similar products turn stools black for several days: once the dose is given, nobody can read that information anymore, not you and not us. Some very dark foods change the colour too. Always tell us what your dog was given and what he ate: we sort it out with you, we don't judge you.
What the stool tells you, and what it does not
What you saw is the first thing we will ask about. Two patterns come up, and they point at different lists of causes. If you can, take a photo: we are used to it, and it is worth a thousand descriptions.
Large, watery stools
A lot of volume, a few times a day, sometimes with weight loss: that points at the upper gut. It is the pattern that dehydrates fastest, because every stool carries away a lot of water.
Small stools, often, with straining
He asks to go out constantly, he strains, he produces little, sometimes with mucus or streaks of blood: that points at the lower gut. Careful with the wording: a dog who strains and produces little is not "constipated", and the fact that some stool or liquid comes out does not mean the road is clear.
The trap: "something is still coming out"
We hear this on the phone all the time, and it proves nothing. A partial blockage lets liquid slip past the object, and diarrhea can absolutely come with an obstructed gut. More insidious still: intense diarrhea can telescope one segment of bowel into the next, often in young dogs, after an infection or with parasites.
What we will ask you
Since when, how many trips outside per day, what it looks like and what colour it is, whether there is mucus or blood, what he might have swallowed, and how he is in between. You do not have to interpret anything: just describe what you see, and we will sort it out with you.
Soft stools in a healthy adult: watching is reasonable
The most common scenario: a healthy adult dog whose stools have gone soft, and who is otherwise completely himself. There, and only there, watching at home is a reasonable choice. And if you would rather call right away, you are exactly where you should be: our Emergency page already lists diarrhea in an alert pet among the reasons to call the same day.
All of these conditions at once
- A healthy adult, with no known illness and no current medication.
- Stools that are soft but not watery, and only a few more trips outside than usual.
- Alert and bright: he wants his normal life back, drinks, eats, plays.
- No blood, no black stools, no vomiting, no pain, no tight belly.
- None of the "go now" signs, and no possible toxin or swallowed object.
How to watch (and for how long)
- Reassess over 24 hours: that is a ceiling, not a timer to run down.
- Note the time of every trip outside, what it looked like and what colour. A photo is genuinely useful, we are used to it.
- Take him out more often and keep things calm: a dog holding it in because he is afraid of making a mess is a miserable dog, and you lose the information.
- Pick up every stool right away, and keep one refrigerated if you think you will be coming in: our collection guide explains how. Collecting a stool sample
- And because you are probably reading this in the evening: if it has not sorted itself out by morning, call when we open. Do not let your 24 hours end on a second night.
One single signal cancels the clock
If he starts vomiting, if the stools go watery or come closer together, if they turn black or tarry, if blood appears, if his belly becomes tight or painful, if he refuses to drink, if he goes flat, or if something worries you and you cannot quite name it: call. One signal is enough, and you do not have to justify which one. The clock does not restart because one stool looked better: it is the whole day that counts, not the last trip outside. And if the clock cancels while we are closed, do not push it to the morning.
This tier is not for everyone
A puppy or a tiny dog, a senior, a dog whose vaccines are not up to date, a pregnant or unspayed female, a dog followed for an illness (kidneys, liver, heart, diabetes, adrenal glands...), a dog on medication, recently operated on, or who has just started a new treatment, especially an anti-inflammatory: for them, we do not watch overnight. Call us the same day, even for "just soft stools", and if we are closed, call an emergency centre rather than waiting for opening. In flat-faced breeds (Bulldog, Pug, Boxer...), it is not the diarrhea itself that worries us: it is what often comes with it, the regurgitation and vomiting they tolerate poorly.
While it lasts, treat every stool as contagious
Until we know what he has, take the precautions: pick up immediately with an inverted bag or gloves, wash your hands with soap and water for at least 20 seconds after every contact with him, his bowl or his back end, and put face-licking on pause. Some germs and parasites in stool do pass to people, and the risk is higher for young children, older adults, immunocompromised people and pregnant women: in your household, they are the ones who stay away from the cleanup. Keep your shoes on in the yard too: some parasites get in through bare skin. Collecting a stool sample · Our services: parasites
And you?
If you have diarrhea too, that call does not come to us: dial 811 to reach Info-Santé, or call your own doctor. We treat animals; for you, they are the right people, and it is up to them to say what is urgent. Just tell them your dog is sick at the same time: it is part of the picture.
Fasting, food and water: what has changed
"I'll starve him for a day and see how it goes tomorrow": that is the most widespread reflex, and the one that has aged worst. Withholding food for a long stretch from an already sick dog weakens him instead of helping, and the gut repairs itself better once it starts receiving small amounts again.
Do not fast him on your own initiative
That is the house rule, and it applies here. If a short digestive rest is useful in his case, your veterinarian will say so, and will also say for how long. A dog who is still interested in his bowl has no reason to be kept from it.
Small, frequent, easy-to-digest meals
Rather than one or two big meals, offer small portions spread through the day. No table scraps, no treats "to comfort him", and no abrupt brand change: a sudden diet change can cause diarrhea all by itself, and it muddies the analysis if we need to run one.
Homemade chicken and rice: neither miracle nor poison
For a day or two it does the job, and if it is the only thing he will accept, it beats a dog eating nothing at all. It simply is not a complete diet: it is missing things a damaged gut specifically needs, and it turns fatty fast depending on the cut you use (skin, dark meat), while a very fatty meal is a classic trigger for pancreas trouble. What matters is not letting it settle in: if your dog is still on it after a few days, the subject is no longer the recipe, it is the diarrhea.
Never cut off the water
Diarrhea loses water fast, and a dog denied water dehydrates faster still: the bowl stays available at all times. If he drinks it all at once and brings it back up, offer small amounts often instead of a big bowl. And if he refuses to drink or cannot keep water down, this is no longer a watch-at-home case: call.
No Pedialyte, no Gatorade, no store-bought broth
Those drinks are dosed with sugar and salt for a human body: in a dog with diarrhea, the sugar can hold even more water in the gut and make the stools looser. Store broths often contain onion or garlic, which are toxic to him. And none of it corrects real dehydration: that is corrected with fluids given at the clinic.
Probiotics, fibre, gut coating products
We get this question every single day on the phone, so here is the honest answer: solid studies do not show that they shorten a diarrhea that has just started, and the most recent international guidance takes no position for or against. They are not dangerous products, but they are not a reason to wait either. If you have already given some, just tell us.
Call us today if...
Between "all is well" and "life-threatening" lies the wide middle: the dog with diarrhea where something is off. In those situations, you call the same day. On the phone we triage with you, and we tell you whether it can wait for an appointment or not. If we are closed and you are hesitating, call an emergency centre: describing the situation costs nothing.
- It has lasted more than 24 hours, or it keeps coming back in waves over days or weeks: that on-and-off pattern is itself the signal (some underlying diseases, of the adrenal glands, the kidneys or the gut, hide behind exactly this rhythm).
- There are streaks of blood or mucus in the stool, even in small amounts.
- He is vomiting too, even if he stays alert between episodes.
- He picks at his food, he has lost weight, or his coat has gone dull.
- He strains often and produces little, or he can no longer hold it indoors although he has been house-trained for years.
- He is on medication, especially an anti-inflammatory: hold the next dose until you have talked to us.
- She is an unspayed female and her last heat was a few weeks ago: pyometra, a uterine infection, often starts with lethargy and digestive signs.
- He is a senior, or followed for a chronic disease: his threshold is simply shorter.
- It has been going on for more than three weeks: this is no longer a passing upset but chronic diarrhea, and it deserves a workup.
Dehydration: you can spot it, you cannot rule it out
Two simple checks at home: gently lift the skin over his back, between the shoulder blades; when he is well hydrated it springs back quickly, whereas it settles slowly in a dehydrated dog. Gums should stay moist and slippery; dry or tacky gums are a warning sign that deserves a call right away. But these are rough indicators: age, thinness and extra weight all distort them, and in a puppy the skin stays springy while the loss is already there. They are there to spot dehydration, never to prove it is absent. So do not use their absence as permission to wait: if the diarrhea continues, call before they show up.
"He is drinking plenty, so he is not dehydrated"
That reasoning costs hours. A dog losing water in every watery stool can lose it faster than he can drink it back. And a marked increase in thirst can itself be the sign of an underlying disease, such as kidney trouble or diabetes, where the dog drinks enormously and dehydrates anyway. Don't spend the evening timing the colour coming back into his gums either: that test needs technique and a stopwatch, and it speaks about circulation, not hydration.
Prepare your call (2 minutes)
- Since when, how many trips a day, and is it speeding up?
- What it looks like: soft or watery, what colour, mucus, red blood, black stools? A photo really helps.
- What he could have swallowed: garbage, table scraps, a bone, a damaged toy, a plant, a household product, a dropped pill?
- His current medications, known conditions, the date of his last dewormer and where his vaccines stand.
- His recent weight if you know it, and whether he is drinking, eating, vomiting.
Bring a sample, but never delay the visit for it
If you have a fresh stool on hand, bring it: about the size of a grape is enough, in a closed container, refrigerated if you cannot come right away, and never frozen. A liquid stool analyses perfectly well, and often tells us more: ideally it reaches us within the hour. But your dog comes before the sample, and we can collect one here. Also tell us if he was dewormed recently: a recent dewormer can mask parasites and produce a falsely negative result. The collection guide, step by step
Puppies and fragile dogs: everything moves faster
With a puppy, you do not "watch" diarrhea: you call the same day, even if he is still playing between stools. And if you are reading this in the evening, "the same day" means tonight. His body has very few reserves, and serious causes are more common than in adults.
Parvovirus
A highly contagious virus that hits puppies hardest, even partially vaccinated ones. Vomiting then diarrhea, often bloody, rapid lethargy: things can tip over in hours. But it usually starts with nothing dramatic at all: he is flat, he turns away from his bowl, he runs a fever, and the blood, when it comes, comes later. So diarrhea without blood in a flat puppy does not mean this is not parvo. The virus persists for months in the environment; Montreal's parks and alleys see it every year.
"He has had his shots" does not mean protected
Until the puppy series is finished, he goes through a window where his mother's antibodies no longer protect him enough and his own have not taken over yet: that is exactly where parvovirus gets in. That is why the series runs to 16 to 18 weeks, and why a single dose is not enough. Call us before coming in with a puppy who has diarrhea: we will bring you in differently, to protect the other dogs. Puppy vaccination
Low blood sugar
A puppy, especially a toy breed, who has diarrhea and skips meals can run out of sugar within hours: weakness, trembling, a wobbly walk, a blank stare. That is an emergency in itself, even if the diarrhea looks mild to you. Do not try to make him drink or swallow anything if he is wobbly: leave.
Worms, and why a negative test does not rule them out
Young animals are very often already carrying worms from birth, passed on by their mother before they were born or through her milk, with no visible sign at all. And one negative stool test does not clear them: some parasites, like giardia, are only shed intermittently. That is why we deworm early, even a puppy in perfect health. Our services: parasites
The simple rule: a puppy with diarrhea more than once, who refuses a meal, or who vomits on top of it, is a same-day call, not a night of observation. With blood, vomiting, or a flat puppy: it is tonight.
The other dogs whose threshold is shorter
A senior, a two or three kilo dog, a pregnant female, a dog followed for an illness (kidneys, liver, heart, diabetes, adrenal glands), a dog on an anti-inflammatory, on steroids, on chemotherapy, or recently operated on: for them, diarrhea does not cost the same. And if your dog is diabetic, do not give his usual insulin dose if he has not eaten or has eaten less than half his portion: talk to us first. Caring for a senior pet · Diabetes in dogs
Give no home medications
Diarrhea is the most self-treated symptom there is, and that is often where the bad evening begins. Human medications are not gentle dog versions: several of them turn a diarrhea that would have settled into a real emergency, and others erase the very information we need.
Imodium and other loperamides
It is the most commonly recommended thing on the internet, and the one that worries us most. A genetic quirk, common in herding breeds but also present in perfectly ordinary crossbreeds whose status nobody knows, lets this drug into the brain: staggering, drooling, lethargy to the point of not getting up, breathing that slows down. And even in a dog who tolerates it, blocking the transit of an infectious or toxic diarrhea keeps inside what the body was trying to push out, and can mask an obstruction that keeps getting worse.
Pepto-Bismol, Kaopectate and friends
They contain a salicylate, a cousin of aspirin, which is absorbed almost entirely into the bloodstream of dogs and cats alike, and which irritates an already inflamed gut. They also turn stools black for several days: they mask melena, the digested blood we are specifically asking you to watch for, and that information does not come back.
Ibuprofen (Advil), naproxen (Aleve), aspirin
Toxic to dogs: stomach ulcers, digestive bleeding, kidney damage. Giving one to a dog who already has diarrhea is pouring oil on the fire.
Acetaminophen (Tylenol)
Dangerous for dogs, and fatal to cats, even a single tablet: give it to no animal in the house.
Leftover prescriptions, including last year's antibiotic
A medication prescribed for another animal, or for another episode, is never a stopgap. Metronidazole in particular is no longer a reflex: we now know it disturbs the gut flora for weeks after the last dose, and recent international guidance is clear, a diarrhea that has just started is not treated with antibiotics by default. The exam decides.
No enemas, and no making him vomit
Never give an enema at home: some of them are frankly toxic to dogs. And do not induce vomiting on your own initiative: doing it at the wrong moment (a corrosive product, a sharp object, a weak dog) can make things worse. Only a veterinarian or a poison line can guide you, in specific cases. Toxic foods and dangerous plants
The one time we ask you to stop a medication yourself
If your dog is on a prescribed anti-inflammatory and he loses his appetite, vomits, or passes black tarry stools: stop the medication and call us. Those are possible signs of a digestive ulcer, and it is the only situation where we would rather you hold a dose before you have even spoken to us.
Frequently asked questions
The questions we hear most on the phone, and one people don't always dare to ask.
He has diarrhea but he is running around and eating. Am I bothering you for nothing?
He got into the garbage. That is surely all it is, right?
Can I give him Imodium just for tonight?
Should I change his food to see if that helps?
It is the middle of the night. Can it wait until morning?
His stool test came back negative last month. So it is not parasites?
I already gave him Pepto-Bismol or Imodium before reading this page. Did I hurt my dog?
Also worth reading
The honest triage, in one sentence
Blood in quantity, black stools, a tight belly, marked lethargy, a puppy going downhill: go now. More than 24 hours, streaks of blood, vomiting on top, or any added sign: call us today. Soft stools in a bright, healthy adult: watch, without going past 24 hours and without letting the clock end on a second night. You do not have to decide alone: sorting it out with you is our job.
Your dog has diarrhea and you are hesitating?
Stop hesitating: call us and we will triage together. If an appointment is enough, we will say so; if it is more urgent, we will point you in the right direction immediately.