Dog Has Diarrhea and Won't Eat: 8 Causes and When It's Urgent

The most common causes

Dietary indiscretion. Your dog ate garbage, table scraps, something spoiled or just something new. It's the number one cause.
A sudden food change. Any switch should be gradual, over about 7 days.
Intestinal parasites. Giardia, coccidia, roundworms or hookworms. Very common in puppies and in dogs that aren't on regular parasite prevention.
Viral or bacterial infections. Parvo is the most serious in unvaccinated puppies: bloody diarrhea, vomiting and severe weakness.
Stress. Travel, boarding, moving, a new baby or a new pet.
Medications, especially antibiotics and anti-inflammatories.
Food intolerances or allergies, which tend to cause diarrhea that comes and goes for weeks.
More serious illnesses: pancreatitis, inflammatory bowel disease, liver or kidney problems, Addison's disease or tumors, especially in older dogs.

When to see the vet

Go to the vet today, or to an emergency vet, if:

There's blood in the stool (red streaks or black, tarry stool).
Your dog is also vomiting repeatedly.
They're very weak or have pale or dry gums.
It's a puppy, especially one that hasn't finished its shots. Puppies dehydrate very fast.
You think they ate something toxic or swallowed an object.
Their belly is painful or swollen.

Make an appointment within 24-48 hours if:

The diarrhea lasts more than a day, or your dog hasn't eaten anything in 24 hours.
Your dog is a senior or has a chronic condition.
The diarrhea keeps coming back over weeks.

What you can do in the first 24 hours

Only for healthy, alert adult dogs with none of the warning signs above:

Make sure they drink. Keep fresh water available at all times. Dehydration is the main risk of diarrhea.
Small, frequent meals. Rather than withholding food for a long time (no longer routinely recommended), offer small portions of an easy-to-digest diet. Your vet can recommend a prescription gastrointestinal diet or a short-term bland homemade diet.
Switch back to their usual food gradually over 3-5 days once the stool firms up.
Write down what you see: number of bowel movements, color, mucus or blood, and whether they eat and drink. It's very useful to your vet.

Avoid human anti-diarrhea medicines. Some, like loperamide (Imodium), can be dangerous for certain breeds such as collies and Australian shepherds, and none should be given without your vet's advice.

What the vet will do

Diagnosis usually starts with an exam and a fecal test to look for parasites. If your dog is weak or the diarrhea isn't improving, your vet may recommend bloodwork, a parvo test or an abdominal ultrasound. Mild cases are treated with diet, probiotics and, if parasites are found, the right dewormer. Dehydrated dogs need fluids, sometimes in the hospital.

In the US, an exam costs about $56-$129 and a fecal test about $58 on average (Synchrony/CareCredit 2025-2026 cost study). Parvo treatment with IV fluids and medication averaged $5,084 in Trupanion's claims data, one more reason to keep puppy vaccines on schedule.

How to prevent it from happening again

Keep up with parasite prevention: here's how often to deworm a dog.
Keep vaccines up to date, especially in puppies: see the puppy vaccination schedule.
Always change food gradually.
Don't let your dog eat street finds or table scraps, and learn which foods dogs can't eat.

Frequently asked questions

How long can diarrhea last in a dog?

Mild diarrhea from something they ate usually clears up in 1-3 days. If it lasts more than 48 hours, keeps coming back or your dog won't eat, call your vet.

Is it serious if a dog with diarrhea won't eat?

A day of low appetite in an adult dog who drinks and has energy usually isn't serious. If they go more than 24 hours without eating, are vomiting or seem weak, see your vet. With puppies, don't wait.

Can I give my dog chicken and rice for diarrhea?

For a day or two, a bland diet can help, but it isn't complete or balanced for longer periods. Ask your vet which diet suits your dog and how to switch back to their regular food.

Sources

This article is for general information and does not replace diagnosis or treatment by a veterinarian. If you are worried about your pet's health, call your vet clinic.