Dog Diarrhoea: The First 24 Hours, and When It Is Serious

Diarrhoea is one of the most common reasons people ring a vet, and most of the time it resolves within forty-eight hours with nothing more than sensible management. The difficulty is that a small number of cases look identical at the start and are dangerous.

Call the vet now if

• Profuse, watery, bloody diarrhoea, particularly with lethargy — this can be haemorrhagic gastroenteritis, which causes rapid, life-threatening fluid loss

• Diarrhoea plus repeated vomiting, which makes dehydration much faster

• A puppy with diarrhoea, especially one not fully vaccinated. Parvovirus is a real possibility and puppies deteriorate within hours

• Collapse, pale or tacky gums, or a dog who will not stand

• Known or suspected poisoning, or a swallowed object

• Severe abdominal pain — hunched posture, praying position, crying when picked up

• A dog with existing disease — kidney, liver, heart, Addison’s, diabetes

• Black, tarry stool, which indicates digested blood from higher in the gut

Call the same day if

• Diarrhoea continuing beyond forty-eight hours

• Any blood, even streaks of fresh red

• Your dog seems unwell in themselves — flat, hiding, not interested in food

• Straining repeatedly and producing little

• Diarrhoea in a senior dog, or one on long-term medication

• Weight loss or recurring episodes over weeks

Probably manageable at home

A bright, playful dog with loose stool, drinking normally and otherwise themselves.

What to do:

• Do not fast a dog with diarrhoea for long. Old advice said twenty-four hours; current thinking favours feeding small amounts of bland food early, because the gut lining heals faster when it is fed. Skip one meal if you like, no more. Never fast a puppy

• Feed small, bland and frequent. Plain boiled chicken with white rice, or plain white fish with pasta, or a veterinary gastrointestinal diet. A quarter of normal portion, four to six times a day

• Keep water available at all times. Dehydration is the real risk

• Add soluble fibre. A spoonful of plain tinned pumpkin, or psyllium husk, helps firm stool for many dogs

• Reintroduce normal food gradually over three days once stool is forming

What not to do:

• No human anti-diarrhoeal medication unless your vet specifically directs it. Loperamide is dangerous in some breeds, notably collies and other herding dogs with the MDR1 gene variant

• No milk. Lactose makes most cases worse

• No treats, chews or table food until it has resolved

Checking hydration

Two quick tests:

Skin tent. Lift the skin over the shoulders and let go. It should snap back instantly. If it falls slowly, your dog is dehydrated.

Gums. They should be moist and pink. Press a finger on them until pale, then release — colour should return within two seconds. Tacky, dry, pale or white gums mean call the vet now.

What causes it

Dietary indiscretion. The most common cause by a wide margin. Bin raiding, something eaten on a walk, a rich treat, a sudden food change.

Stress. Kennelling, a house move, fireworks, new people. Stress colitis typically produces loose stool with mucus and sometimes fresh blood at the end — and it usually settles within a couple of days.

Parasites. Giardia, roundworm, whipworm, coccidia. Common in puppies and in dogs who drink from puddles and streams. Needs a faecal test, because worming products do not all cover all parasites.

Infection. Viral or bacterial. Parvovirus in unvaccinated puppies is the one to fear.

Chronic disease. Food-responsive enteropathy, inflammatory bowel disease, pancreatic insufficiency, and others. These show as recurring or persistent diarrhoea, often with weight loss, and need investigation rather than management.

Small bowel or large bowel?

This is what your vet will want to know, and it narrows the cause considerably.

Large bowel signs: small amounts, very frequently, with straining, mucus and fresh red blood. Colitis.

Small bowel signs: large volumes, less frequent, often watery, sometimes with weight loss. More often from the upper gut.

You can work this out at home, and it genuinely helps the consultation.

Probiotics

There is reasonable evidence that specific canine probiotic strains shorten the duration of acute diarrhoea. They are not a treatment for a serious case, but for an ordinary upset they are a sensible thing to have in the cupboard.

Prevention

• Change foods gradually, over five to seven days
• Secure bins and compost
• Work on “leave it” for scavenging
• Keep worming and parasite prevention current
• Avoid stagnant water on walks
• Do not feed cooked bones, fatty leftovers or rich treats

Keep a record

If diarrhoea is recurring, write down dates, what the stool looked like, what your dog ate, and anything unusual that week. Patterns emerge from records that never emerge from memory, and it is the single most useful thing you can bring to an appointment.