Diarrhea
Diarrhea in pets means looser, wetter or more frequent stools, ranging from a mild dietary upset to a sign of serious underlying illness.
Also known as Loose Stool, Upset Stomach
Diarrhoea simply means your pet is passing looser, wetter, or more frequent stools than normal. It is one of the most common reasons owners end up at the vet: UK data on primary care practices found that around 1 in 12 dogs is diagnosed with an acute episode each year, and most of these cases involve only a single vet visit before resolving. Despite how common and often mild it is, diarrhoea matters because it can signal anything from a simple dietary upset to a serious underlying illness, and figuring out which is which shapes how it should be managed.
Vets generally sort diarrhoea by how long it has lasted and where in the gut it seems to be coming from. Diarrhoea lasting under two weeks is usually called acute, while anything running longer is chronic and tends to need more investigation. Location matters too: diarrhoea from the small intestine often comes with larger volumes of stool, possible weight loss, and vomiting linked to eating, while diarrhoea from the large intestine (the colon) tends to involve smaller, more frequent stools, straining, mucus, or fresh blood. Vets use this pattern, alongside your description of the stool, to narrow down likely causes before running any tests.
The underlying causes are wide-ranging. Dietary indiscretion (eating something they shouldn't), sudden diet changes, food intolerances, intestinal parasites, and bacterial or viral infections are common triggers of short-lived episodes. Diarrhoea can also be a symptom of something happening outside the gut entirely, such as kidney, liver, or hormonal disease, which is why persistent or severe cases warrant fuller bloodwork rather than just fecal tests. Chronic diarrhoea in particular often falls under what's called chronic inflammatory enteropathy, an umbrella term for ongoing gut inflammation, and the encouraging news is that many of these dogs improve significantly just from a change in diet, without needing more intensive treatment.
Most mild, uncomplicated cases settle on their own with supportive care, and current veterinary guidance actually advises against reaching for antibiotics in dogs with mild to moderate diarrhoea, even when it contains blood, since antibiotics don't address the underlying cause and can disrupt gut bacteria further. That said, some signs mean it is time to get your pet seen rather than wait it out:
- Diarrhoea containing a noticeable amount of fresh blood, or looking black and tarry
- Ongoing vomiting alongside the diarrhoea
- Lethargy, reduced appetite, or a swollen or painful abdomen
- Diarrhoea lasting more than a couple of days, or recurring repeatedly
- Any diarrhoea in a very young, elderly, or already unwell animal
A vet visit lets your pet be examined properly, hydration checked, and, if needed, stool or blood tests run to work out what's actually going on rather than guessing. The guides below go deeper into specific causes, diagnostic paths, and treatment options.
