Your dog produced something this morning that was not a normal stool, and you are now standing in the garden trying to decide whether this is a wait-and-see or a get-in-the-car.
That is the actual question, and most articles do not answer it. They list twenty causes of diarrhoea, dietary indiscretion, parasites, stress, pancreatitis, cancer, and leave you no better off than when you started.
So this guide does two things instead. It gives you a way to grade what you are looking at, and it tells you what the evidence says about the treatment your vet is most likely to reach for.
What is the difference between loose stools and diarrhoea?
There is no clean line. It is one spectrum, and the useful way to talk about it is the Purina faecal score, 1 to 7.
| Score | What you're looking at | What it means |
|---|---|---|
| 1-2 | Hard, dry, crumbly | Too firm; consider hydration and fibre |
| 3-4 | Log-shaped, holds form, leaves little residue | Normal |
| 5 | Soft, still holds a shape when lifted, leaves residue | Loose stool |
| 6 | No shape, piles rather than forms, texture of thick batter | Diarrhoea |
| 7 | Watery, a puddle, no texture at all | Diarrhoea, and losing fluid fast |
Learn to name the number. "He's got a bit of a loose motion" tells your vet almost nothing; "he's been a 6 since yesterday morning, was a 4 before that" tells them a great deal.
The trend matters more than the score. A dog sitting stably at a 5 for two days has a different problem from a dog that went 4 → 7 overnight. And a single 6 followed by two normal stools is not an illness. It is a dog that ate something.
Does my dog need to see a vet right now?
Some of this genuinely cannot wait. Go now if you see:
- Blood in quantity, or stool that looks like raspberry jam
- Repeated vomiting alongside the diarrhoea, the combination is what causes dangerous fluid loss
- A puppy under six months, especially if unvaccinated. Bloody diarrhoea plus vomiting in an unvaccinated puppy is a parvovirus question until proven otherwise, and that is measured in hours
- Pale, white or tacky gums
- Unable to keep water down
- A tense, painful belly, or a dog standing in a hunched, praying position
- Collapse, or lethargy well beyond "a bit off"
Call today, but it is not an emergency, if: the diarrhoea has run more than 48 hours, your dog is an unwell senior, there is a known chronic condition, your dog is on medication, or there is a small amount of fresh blood in an otherwise bright and well dog.
Watch at home if: your dog is bright, drinking, not vomiting, has a soft belly, and this started within the last day or so.
That last category is the majority of cases. Which brings us to the part worth arguing about.
Why is metronidazole usually the wrong answer?
Because the trials have been done, and the answer is not the one Indian veterinary practice is built around.
Metronidazole (you will see it as Metrogyl, Flagyl, Metron) is the reflex prescription for canine diarrhoea across most of India. Your dog has loose stools, you go to the clinic, you come home with metronidazole. Often nobody examined a stool sample.
Here is what the evidence shows:
- A randomised, double-blind, placebo-controlled trial published in the Journal of Veterinary Internal Medicine tested metronidazole against placebo in dogs with acute diarrhoea. It did not deliver the clear benefit its ubiquity implies.
- A separate randomised, double-blind, placebo-controlled trial comparing a probiotic against metronidazole for acute canine diarrhoea found no advantage to the antibiotic.
- A 2022 randomised controlled trial in JAVMA found that nutritional management was superior to metronidazole for treating acute colitis in dogs.
- Across these studies, the consistent finding is that metronidazole measurably worsens the gut microbiome, the canine dysbiosis index shifts in the wrong direction, and recovery can take weeks and may be incomplete in some dogs.
Read that as a whole: for uncomplicated acute diarrhoea, the standard antibiotic does not reliably shorten the illness, and it damages the microbial population your dog needs to recover, sometimes for longer than the illness would have lasted.
This is not an argument that metronidazole is never indicated. There are real uses: giardia, some specific infections, certain inflammatory bowel cases, dogs that are genuinely septic. Those are diagnoses, made by a vet, usually with a test.
What the evidence does not support is metronidazole as the default response to a dog that had a bad stool yesterday.
How to have this conversation without being difficult: ask "is there something specific you're treating with this, or is it precautionary?" It is a fair question, most vets will answer it straight, and it changes the conversation from refusal to collaboration. If your dog is unwell enough that your vet wants to treat empirically, that is a legitimate call, but you should know which one is being made.
Should I starve my dog?
Not the way you were probably told.
The old advice, withhold food for 24 to 48 hours, "rest the gut", has moved. Current guidance from veterinary nutrition sources is that a short fast of 12 to 24 hours is reasonable when there is vomiting, but prolonged fasting beyond about 48 hours should be avoided: it thins the intestinal lining, delays the return of normal gut function, and worsens dysbiosis. Fasting has been associated with reduced villus height and increased risk of bacterial translocation.
The gut lining feeds itself partly from what passes through it. Starve it and you slow its repair.
What to do instead, feed small, bland and often:
- A quarter of the normal portion, four to six times a day, rather than two full meals
- Boiled chicken and plain rice is the standard for a reason: low fat, low residue, easy
- Plain cooked pumpkin genuinely helps stool consistency and is worth keeping in the house
- Water available constantly, never restrict it
- Rebuild to the normal diet gradually across three to five days once stools firm up
Do not give human anti-diarrhoeals. Loperamide (Imodium) is dangerous in some dogs, herding breeds with the MDR1 mutation especially, and stopping gut motility when there is an infection to clear is the wrong direction.
What if this keeps happening?
Recurrent loose stools are a different problem from one bad week, and the answer is diagnostic rather than therapeutic.
Worth getting done: a faecal test for parasites, giardia is common in India and frequently missed on a single sample, so ask about repeat testing or antigen testing. Then a proper look at the diet, including everything the dog picks up on walks and everything the household feeds unofficially.
Worth doing yourself for two weeks: write down every stool with its score and every single thing the dog eats. It is tedious, and it identifies the cause more often than any first-line test.
If the pattern is chronic, months, not weeks, this stops being a diarrhoea question and becomes a chronic enteropathy question, which needs a vet working through diet trials and bloodwork rather than another course of antibiotics.
The bottom line
Grade it, don't guess it, learn the 1-to-7 score and watch the trend.
Most acute loose stools in a bright, drinking, non-vomiting dog resolve in a couple of days with small bland meals and no drugs at all. The antibiotic that gets handed out for it does not reliably help and does measurable harm to the gut it is meant to fix.
And the situations that genuinely cannot wait, blood, repeated vomiting, an unvaccinated puppy, pale gums, collapse, are worth memorising, because those are the ones where hours matter.
Not sure where your dog sits? A bright, playful dog with soft stools and a normal appetite can be watched at home. A flat dog with watery stools, or any puppy, should be seen.