Dog Diarrhoea and Digestive Issues: What to Log and When to Call the Vet

Dogs get upset stomachs. Most of the time it's self-limiting, dietary - something they ate on yesterday's walk, a treat that didn't agree with them, a sudden food change - and it resolves within 24 hours without any intervention beyond withholding food for a meal.

The problem is that chronic or recurring digestive issues often look like a string of individual one-offs. Each episode gets written off. It's only when you look at a log and see five episodes in three months that the pattern becomes visible - and with it, the suggestion that something more than bad luck is driving it. According to NOAH (National Office of Animal Health), an estimated 1 in 7 dogs in the UK carries fleas at any given time, and 86.6% of soil samples taken from UK and Irish parks contain roundworm eggs - making parasitic causes of digestive issues far more common than many owners realise.

Acute vs chronic

Acute diarrhoea starts suddenly, has an obvious possible cause, and resolves quickly. Your dog raided the bin, ate grass, was given a rich treat by a well-meaning visitor, or drank from a puddle. One to two days of loose stools followed by a return to normal is typically acute diarrhoea. It doesn't usually need veterinary treatment.

Chronic diarrhoea is recurring or persistent - loose stools more days than not, or episodes that keep coming back. This warrants investigation. Common causes include parasites, inflammatory bowel disease (IBD), food sensitivity, small intestinal bacterial overgrowth, and less commonly, more serious conditions.

The distinction matters because the management is completely different. Acute episodes need rest and time; chronic issues need diagnosis.

What to log

When your dog has a digestive episode, note:

• Date and time
• Frequency - how many times, over what period
• Consistency - soft, liquid, or watery (Bristol stool scale 6–7)
• Blood or mucus - blood always warrants a call to the vet; mucus in large bowel diarrhoea is common and less alarming, but mention it
• Vomiting alongside - combined vomiting and diarrhoea is a more significant presentation than either alone
• Their energy and appetite - a dog with diarrhoea who's still bright and eating is lower concern than one who's flat and off food
• What they ate or were exposed to - anything different in the past 24 hours: new food, treats, access to the garden, any scavenging you noticed on the walk

The 24-hour rule

For an otherwise healthy adult dog with straightforward diarrhoea and no blood:

• Withhold food for 12–24 hours to let the gut rest (keep water available)
• Offer a bland diet (plain cooked chicken and white rice, or Hills i/d if you have it) for 24–48 hours
• Gradually reintroduce normal food

If it's not improving after 48 hours, call the vet. If it worsens, or if blood appears, call sooner.

The 24-hour rule is for adult dogs. Puppies and small dogs can become dehydrated much faster - if a puppy has diarrhoea that isn't resolving quickly, call your vet on the same day.

When blood in the stool matters

Red blood (fresh blood, bright red) can come from the large intestine or rectum - often from colitis (large bowel inflammation), a rectal polyp, or straining. Occasionally alarming-looking bright red diarrhoea is haemorrhagic gastroenteritis (HGE), which comes on suddenly, can be quite severe, and needs veterinary treatment quickly.

Dark, tarry stools (black, sticky, foul-smelling) indicate digested blood from higher up in the digestive tract - stomach or small intestine. This is more significant and should be assessed promptly.

Any blood in stool is worth calling your vet about, even if the dog seems otherwise fine.

The trigger pattern problem

Many dogs with chronic digestive issues have triggers - dietary, environmental, or stress-related - that only become visible when you look across multiple episodes. Seasonal patterns suggest environmental allergens. Episodes after specific foods suggest dietary sensitivity. Episodes correlating with stressful events suggest a stress-reactive gut.

Without a log, these patterns are invisible. With a log, they sometimes explain something that had seemed random.

One of the most practical uses of a health journal is identifying the pattern in what looks like repeated bad luck.

Common causes beyond diet

For the most common causes of recurring digestive issues, see the monitoring guides for inflammatory bowel disease, colitis, and pancreatitis.

Giardia and other intestinal parasites - particularly in dogs who swim in lakes or streams, or interact with other dogs in parks. Giardia specifically causes intermittent soft stools that can persist for months if untreated. A faecal test will identify it. The PDSA PAW Mini Report 2025 found that 84% of UK dog owners worm their dogs, but that still leaves around 1.7 million dogs without any worm protection - a significant contributor to the parasitic digestive issues vets see regularly.

Inflammatory bowel disease - chronic inflammation of the GI tract causing recurring vomiting, diarrhoea, and weight loss. Managed with diet and often medication.

Pancreatitis - inflammation of the pancreas, often triggered by fatty food. Causes vomiting and diarrhoea with abdominal pain. Common in Miniature Schnauzers and Cocker Spaniels.

Food sensitivity - not a true allergy in most cases, but a chronic inflammatory response to a specific protein. Often improves significantly on a hydrolysed or novel protein diet.

Frequently Asked Questions

My dog has diarrhoea but seems completely normal otherwise. Should I still call the vet? If it's a single episode and they're bright, eating, drinking, and showing no blood - probably not immediately. Manage it at home with the 24-hour approach. Call if it hasn't resolved in 48 hours, if it worsens, or if anything else changes.

What's the best food for a dog with an upset stomach? Plain boiled chicken (no seasoning, no skin) and white rice in a 1:3 ratio is the traditional bland diet. Hills Prescription Diet i/d is a commercial option that many vets recommend. The goal is easily digestible, low-fat, and consistent - not tempting or varied.

My dog has loose stools regularly, maybe once a week. Is that normal? No - a dog with regular loose stools is showing something worth investigating. The cause might be dietary (a food that doesn't agree with them), parasitic (a regular infection source), or a chronic condition. It's worth a vet conversation and probably a faecal test as a starting point.

Could stress cause recurring diarrhoea? Yes. Some dogs have what's sometimes called stress colitis - the gut is sensitive to psychological stress, and anxiety-provoking events (travel, new environments, changes in routine) reliably cause loose stools. If your dog's episodes correlate with stressful events, this is a pattern worth identifying and worth discussing with your vet - there are management strategies.