Diarrhea in Dogs: Common Causes and When to Worry

One bout of loose stool in a dog who is eating, drinking and acting normal is often mild and settles within two or three days. Call your vet if it lasts longer than that, if there is blood or black, tarry stool, or if your dog is a puppy, a senior or seems unwell.

Diarrhea is a symptom, not a disease. It can come from something as simple as a rich treat, or from an infection or illness that needs treatment. This guide sticks to practical steps at home and at the vet. For a quick overview of the symptom itself, see our diarrhea symptom page.

What counts as diarrhea

Healthy dog stool is firm and easy to pick up. Diarrhea happens when food moves through the gut too quickly for water to be absorbed, so the stool comes out softer than normal, anywhere from slightly loose to fully liquid.

Vets often think of it as acute, meaning sudden and short-lived, or chronic, meaning it lasts for weeks or keeps coming back. Many acute cases settle with simple care, while diarrhea that persists or recurs usually needs testing to find the cause. What helps your vet most is how long it has lasted, how often it happens and what else is going on.

Common causes

Dogs get diarrhea from many things:

• Dietary indiscretion. Raiding the trash, eating spoiled food, or snacking on rich table scraps or toxic foods such as chocolate.
• Sudden diet changes. A quick switch of food can upset the gut.
• Stress. Travel, boarding or a vet visit can all do it.
• Intestinal parasites. Giardia, coccidia, and roundworms, hookworms and whipworms are common examples.
• Infections. Viral illnesses such as parvovirus and distemper, and bacterial infections.
• Medical conditions. Food allergies, inflammatory bowel disease, pancreatitis, liver, kidney and other organ problems, and cancer.
• Medications and swallowed objects. Some drugs upset the gut, and a foreign object or toxin can too.

You will not always be able to tell the cause from looking at the stool, so the other signs your dog shows count for a lot.

When to call your vet

Do not wait it out if your dog has any of these:

• Blood in the stool, or black, tarry stool
• Vomiting along with diarrhea (see our guide to vomiting in dogs)
• Lethargy, weakness, belly pain, fever or loss of appetite
• Signs of dehydration, such as dry or sticky gums or low energy
• Diarrhea in a puppy, which can turn serious quickly
• Diarrhea in a senior dog or a dog with a health condition
• Any chance your dog ate a toxin or swallowed an object
• Loose stool lasting more than two days (Cornell says to act if it does not resolve in 48 to 72 hours)

Puppies need extra care. Diarrhea in a puppy can be a sign of parvovirus, a viral infection that can be life-threatening, especially in young or unvaccinated dogs. Our puppy vaccination schedule explains how vaccines protect against it. If your puppy has diarrhea, call your vet the same day.

If you suspect poisoning, call your vet, an emergency clinic, ASPCA Animal Poison Control at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661 (US; fees may apply). Outside the US, call your local emergency vet.

Home care for mild diarrhea

If your dog is otherwise healthy and cheerful, you can support them at home for a day or two. Check with your vet if you are unsure.

• Keep water available. Diarrhea drains fluid quickly, and vomiting makes dehydration faster. Offer fresh water and frequent trips outside.
• Ask your vet about a food break. Sources differ. Some suggest holding back food for several hours or up to a day in a healthy adult, while others skip fasting and recommend small, frequent bland meals instead. Do not fast a puppy, senior or dog with a medical condition unless your vet says to.
• Feed bland meals. Small, frequent portions of plain boiled, skinless chicken with white rice are the usual suggestion. Avoid any ingredient your dog is allergic to.
• Try a little pumpkin. Plain canned pumpkin, not pie filling, is high in soluble fiber and can help firm up stool. See can dogs eat pumpkin for serving tips.
• Ask about probiotics. Some vets recommend them, but product quality varies, so check with yours before buying one.

Bland diets are not nutritionally balanced, so use them for a short time only. Once stools are normal, move back to the regular food gradually over about a week. If the diarrhea started after a food change, your vet may suggest going back to the old food until stools firm up. Avoid rich treats and extras until stools are back to normal.

What not to give

Do not give human anti-diarrhea medicine unless your vet says to. Cornell specifically warns against Pepto-Bismol and Imodium. VCA explains why: products with bismuth subsalicylate can be toxic to dogs at high doses, and loperamide slows the gut, which can worsen a blockage or keep parasites inside. AKC adds that most human drugs are ineffective for dogs, and some are harmful.

What to bring to the vet

Take a fresh stool sample in a clean bag, since your vet can use it to check for parasites. Also be ready to describe:

• When the diarrhea started and how often it happens
• The color, consistency and smell of the stool
• Any recent changes in food, treats or environment
• Vaccination and parasite prevention history
• Other signs, such as vomiting, appetite changes or lethargy

Your vet may order a fecal test, blood work or X-rays if a blockage is suspected, and may treat dehydration with fluids. Depending on the cause, treatment can include deworming, a therapeutic gut-friendly diet or medicine your vet prescribes. For mild cases, testing may wait unless the diarrhea does not improve within a couple of days.

Preventing diarrhea

Not every case can be avoided, but a few habits help:

• Switch foods gradually, mixing the new food in over a week or two rather than overnight
• Supervise outdoor time and discourage scavenging from the trash or the ground
• Keep vaccinations and the parasite prevention your vet recommends up to date
• Discourage drinking from puddles and stagnant water
• Limit rich treats and table scraps

Written from veterinary sources by the Pawsplained editorial team. Not yet reviewed by a veterinarian; this is general information, not a diagnosis or treatment plan. Updated Oct 30, 2026. Editorial policy