Loose stools can follow a change in food, an infection or something a dog should not have eaten. The appearance of the stool is useful information, but it cannot tell you the cause on its own. Your dog's age, energy, appetite and other symptoms matter just as much.
What can cause diarrhea?
Possible causes include diet, parasites, infections, underlying illness and intestinal obstruction. A sudden food change, scavenging or an unfamiliar treat can upset the digestive tract. Parasites and infectious diseases are other possibilities, particularly in puppies or dogs with exposure to other animals.
Recurring diarrhea may need a different investigation from a single loose stool. Diseases affecting the intestines or other organs can produce similar signs. Food intolerance and food allergy are different problems, and neither can be diagnosed simply from the color of a bowel movement. Even an obstruction can sometimes involve diarrhea, so passing stool does not rule one out.
What to record
Note when the problem started, how often your dog needs to go and whether there is straining. Take a photograph if that is easier than describing the stool. Tell the clinic about blood, black or tarry stool, mucus, vomiting, appetite changes and anything your dog may have swallowed.
Bring a list of foods, treats, medications and supplements. Ask the clinic whether it wants a fresh stool sample and how to transport it. Keep children and other pets away from stool and wash your hands after cleaning up.
When to contact a veterinarian
Seek urgent care for collapse, marked weakness, a painful or swollen abdomen, repeated vomiting, substantial bleeding or suspected poisoning or foreign-body ingestion. Puppies, senior dogs and dogs with existing disease deserve prompt advice because a seemingly small change can be more consequential for them.
For an otherwise alert adult dog, call your clinic for advice if diarrhea persists, recurs or worsens. Do not wait for a fixed number of hours when your dog seems unwell. A veterinarian can decide whether an examination, stool testing, blood work or imaging is appropriate.
Food, water and medicines
Keep fresh water available unless your veterinarian gives specific instructions. Ask for an individual feeding plan; fasting is not appropriate for every dog. Do not give human anti-diarrheal medicines, leftover prescriptions or supplements without checking that they are suitable for this dog and this episode.
For prevention, keep rubbish and tempting hazards out of reach, make planned food changes gradually and follow your veterinarian's vaccination and parasite-control recommendations. These measures reduce some risks without guaranteeing that diarrhea will never occur.