Dog Diarrhoea: What to Do Tonight and When to Call the Vet
It is late. Your dog woke you, wanted out, and what came out was not right. You have two questions: what do I do now, and how long can I wait before this needs a vet? Here are both, in that order.
What to do in the next 24 hours
If your dog is an adult, bright in themselves, and this is the first bout, you can manage the first day at home.
Diarrhoea loses fluid fast. Keep the bowl full so the dog can replace it as they go.
Twelve to 24 hours without food lets the gut settle, and in simple cases the diarrhoea often improves in that time on its own. Do not go beyond a day.
Three or four small meals a day rather than one or two. Boiled skinless chicken or white fish with rice or mashed potato is the classic, because it is low in fat and easy to digest. Or their usual complete food at about a quarter of the normal daily amount. Build back to normal over two or three days.
No treats, chews, dental sticks or scraps until the stool is firm. Chews are rich in connective tissue and fat and are one of the most common triggers in the first place.
Act at the first sign. If you notice the stool going soft, cut the portion a little and remove treats and chews straight away. Most bouts can be headed off before they become diarrhoea at all.
Why it happened
Diarrhoea is a symptom, not a disease, and it has a long list of possible causes. In practice the most common ones are ordinary: a food change made too fast, a rich chew, an overly large meal, something scavenged on a walk, or a parasite picked up outside. Infections, food intolerance, enzyme problems, pancreatitis and organ disease are all possible too, and become more likely the longer it goes on or the more often it comes back.
Which is why the second question matters more than the first.
- your dog is a puppy or an older dog. Both lose fluid quickly and can go downhill in a day or two. Do not withhold food from either; let the vet decide.
- the stool is black or tarry. That is digested blood from higher up the gut and is always taken seriously, whatever the consistency.
- there is a lot of blood, or blood together with vomiting.
- your dog is vomiting, bloated, has a gurgling or painful belly, an arched back, or is panting or groaning.
- your dog is not themselves: quieter, sleeping more, off their food, keeping away from you. These subtle changes often mean pain or nausea.
- it has lasted more than 48 hours.
Bright red streaks on the surface of a stool look alarming but usually come from irritation right at the end of the bowel and are rarely serious on their own. If they persist, mention them to the vet.
Take the vaccination record with you, a note of everything eaten in the last three days including treats and chews, and a photo of the stool if you are not sure whether there is blood in it. It saves the vet guessing.
When mild diarrhoea is the bigger problem
A bout that lasts two weeks, or keeps coming back every few days, is chronic even when each episode seems mild. Chronic diarrhoea is not something to live with. It can be an early sign of a problem with the pancreas, liver or kidneys, and the repeated bouts damage the gut lining and its bacterial balance over time, to the point where bland diets and even prescription foods stop working. It needs a proper work-up: blood tests, sometimes imaging, and often an exclusion diet.
If your dog is a repeat offender, write down everything, with product names and amounts in grams. When the next bout comes, the diary is how you and your vet track down the trigger.
Once it settles
Consistency keeps it settled. Same food, same amounts, same meal times. Any change of food made slowly: at least four days for a normal dog and ten for a sensitive one (here is the schedule). And a healthy scepticism about tips from the internet and dog-walking friends: before you change the feeding or any medication, ask the vet who knows your dog.
If you would like a second pair of eyes on the diet once your vet has ruled out the medical causes, send us the name of the current food and treats and we will look at whether they are part of the picture.
Written with the Happy Dog veterinary team. Based on "On the trail of the runs" by Cornelia Günther, veterinarian, and "Vomiting, diarrhoea, constipation: which dietary measures make sense?" by Pascale Huber, veterinarian. Reviewed for Happy Dog UK, September 2026. General information, not a substitute for advice from a vet who has examined your dog.
- Günther, C.: Dem "Dünnpfiff" auf der Spur. Happy Dog & Happy Cat VET, April 2021.
- Huber, P.: Erbrechen, Durchfall, Verstopfung: Welche diätetischen Maßnahmen sind sinnvoll? Happy Dog & Happy Cat VET, August 2023, after Dahlem, D., akademie.vet.
- Mohr, A.J. et al.: Effect of early enteral nutrition on intestinal permeability, intestinal protein loss, and outcome in dogs with severe parvoviral enteritis. J Vet Intern Med 2003;17:791–798.
