Few things worry a dog owner more than their dog getting diarrhoea. The good news: a large proportion of cases are mild and resolve on their own. The bad news: the same symptom can also be the first sign of a life-threatening infection. In this guide you will find out when it is enough to keep an eye on things at home, when you need to see a vet straight away, what you can do for your dog at home, and how to screen for the most common infectious causes in just a few minutes.
What counts as diarrhoea?
We speak of diarrhoea when the stool is softer than usual, unformed or watery, or when the dog passes stool more often than usual. It is important to observe the colour, consistency and smell and any accompanying signs – these reveal a lot about the severity and also help your vet. Yellowish, mushy stool often points to a digestive upset; a mucous or jelly-like coating may indicate irritation of the large intestine; black, tarry stool can mean digested blood (bleeding in the upper digestive tract), while fresh red streaks can mean bleeding from the large intestine or rectum.
When is a dog's diarrhoea harmless?
A single soft stool is often nothing serious. The problem is typically mild and temporary if the dog is otherwise well: eating, drinking, lively, has no fever, and the stool returns to normal within 24–48 hours. Common, harmless triggers:
- Dietary indiscretion: a sudden change of food, raiding the bin, fatty leftovers, unfamiliar treats.
- Stress: travel, moving house, a new family member, boarding kennels, stormy weather.
- Sensitive stomach: some dogs are simply more prone to soft stools.
What to do in these cases: a light, bland diet, fresh water available at all times, and observation. If your dog's condition gets worse, or there is no improvement within 48 hours, it is no longer worth waiting.
When is diarrhoea a warning sign? – see a vet immediately
There are situations in which diarrhoea is an emergency. See a vet immediately if you notice any of the following:
- Bloody or black, tarry stool
- Repeated vomiting, especially if your dog can't even keep water down
- Lethargy, weakness, collapse, high or low body temperature
- Signs of dehydration (dry gums, sunken eyes, skin that springs back slowly)
- Diarrhoea in a puppy – in puppies, fluid loss can become life-threatening within hours
- Severe diarrhoea with incomplete or uncertain vaccination status
- Severe, persistent bloating or abdominal pain, restlessness
- An elderly dog or one with a chronic illness (kidney, liver, diabetes)
In puppies and unvaccinated dogs, severe, often bloody diarrhoea can be a classic symptom of parvovirus – this requires urgent veterinary care.
If the diarrhoea is accompanied by vomiting, or vomiting is the main symptom, also read our guide to vomiting in dogs: it explains what the colour of the vomit means and when you need to see a vet immediately.
How to recognise dehydration at home
Diarrhoea (especially together with vomiting) can quickly lead to dehydration, which is dangerous in itself. Two simple checks you can do at home:
- Skin test: gently lift the skin between the shoulder blades and then let go. If it settles back slowly and sluggishly, this indicates dehydration.
- Gum test: your dog's gums should be moist and pink. Dry, sticky gums or slow capillary refill (the colour returns slowly after pressing) is a warning sign.
If you suspect dehydration, don't wait – this is especially urgent in puppies and elderly dogs.
The most common causes of diarrhoea in dogs
Dietary and environmental causes
The most common are: a change of food, spoiled or fatty food, foreign material (grass, bones, rubbish), food intolerance, and stress. These are usually mild and resolve with a change of diet.
Parasitic causes – Giardia and intestinal worms
Giardia is one of the most common, and often misdiagnosed, causes of chronic, recurrent, foul-smelling diarrhoea. It can be detected at home with the Giardia rapid test. Details: Giardia in dogs.
Viral causes – parvovirus and coronavirus
Parvo is the most common life-threatening cause in puppies: severe, often bloody diarrhoea, vomiting, rapid deterioration. It can be screened for at home in minutes with the parvovirus (CPV) rapid test. More: Parvovirus in dogs. Canine coronavirus (CCV) is a common but underestimated cause of diarrhoea, and alongside parvo it can make the condition more severe – see: Canine coronavirus (CCV).
Bacterial and other causes
Bacterial infections (e.g. Salmonella, Campylobacter), inflammatory bowel disease, pancreatitis and poisoning (human medicines, chocolate, xylitol, plants) can also cause diarrhoea – the latter are often urgent.
Home care step by step (in mild cases)
- Fluid replacement: always have fresh water available. Preventing dehydration is the most important thing.
- Light, bland diet: vets today generally do not recommend prolonged fasting. Give small portions of easily digestible food (e.g. boiled lean chicken without skin or seasoning, with boiled rice) for a few days, then gradually return to the usual food.
- Small portions, often: a large portion puts strain on the stomach; it is better to split the daily amount.
- Observation: note down how often your dog passes stool, its consistency, any vomiting and your dog's general condition.
- See a vet if things get worse: if there is no improvement within 24–48 hours, or any of the warning signs appears, don't continue treating at home.
What NOT to give your dog
- Don't give human medicines (e.g. anti-diarrhoeal products) without your vet's advice – some of them are toxic to dogs.
- Don't make your dog fast for long, especially a puppy or a small dog.
- Don't suddenly change food while your dog is recovering.
How to find out at home what is behind the diarrhoea
Because parvo, corona and Giardia cause similar symptoms but require completely different action, it is worth screening for all three at once. That is what the 3-in-1 (parvo + corona + Giardia) combo rapid test is for – or, if you also want to rule out distemper because of coughing or a runny nose, the 4-in-1 rapid test, which tests for these three together with distemper. The result is ready in about 10 minutes, and you arrive at the vet with concrete information. The test does not replace a veterinary diagnosis – but it helps you decide how urgent the situation is. You can read about how reliable a rapid test result is and when it is worth repeating here: How accurate is a home rapid test? Which route is right when? This will help: Home rapid tests: when to use one and when to see a vet
Prevention: how to reduce the risk of diarrhoea
- Change food gradually over 5–7 days when switching to a new food.
- Regular deworming and parasite screening, especially for dogs in multi-pet households or that mix with other dogs.
- A complete vaccination programme, especially for puppies (parvo, distemper).
- Prevent bin raiding and spoiled food; keep the bin closed.
- In stressful situations (travel, boarding kennels), keep to a calm, predictable routine.
Frequently asked questions
What can I give my dog for diarrhoea at home?
In mild cases, the key is a light, bland diet (e.g. boiled lean chicken with rice) and fresh water at all times. Don't give human medicines without your vet's advice. If there is no improvement within 48 hours, or your dog's condition gets worse, see a vet.
How long can harmless diarrhoea last?
Mild, diet-related diarrhoea usually resolves within 24–48 hours. Problems that last longer or get worse need to be investigated.
How do I know if it's parvo?
Severe, often bloody diarrhoea, vomiting and rapid deterioration suggest parvo, especially in a puppy or an unvaccinated dog. At home, the CPV rapid test helps within minutes, but if it is positive you must see a vet immediately.
Can I give my dog a probiotic?
Vets often recommend a veterinary probiotic to restore the gut flora. Ask for a recommendation for a suitable product made for dogs – human products are not always appropriate.
When is bloody diarrhoea urgent?
Bloody or black, tarry stool should always be taken seriously, and in a puppy or an unvaccinated dog, or when accompanied by vomiting or lethargy, it requires immediate veterinary care.
Important: MancsLab rapid tests are intended for preliminary screening at home and do not replace a veterinary diagnosis.