When your dog suddenly starts throwing up and has diarrhea at the same time, it’s alarming and often feels like the situation escalated out of nowhere.
These two symptoms together usually signal that something has irritated or overwhelmed the digestive system — sometimes mildly, sometimes seriously.
This guide outlines the common causes of sudden vomiting and diarrhea in dogs, what you can do at home, and when to seek veterinary help.
Dog Suddenly Throwing Up and Diarrhea: Why It Happens
A sudden episode of vomiting and diarrhea in dogs is most often caused by dietary indiscretion, infections, parasites, toxin exposure, stress, or underlying disease.
When these symptoms appear together, the digestive system is reacting quickly and forcefully, trying to remove something harmful or struggling to function normally.
Food-related issues, gut infections, abrupt diet changes, or kidney and liver disorders can trigger both symptoms rapidly.
Some causes are mild and resolve within a day, while others can progress into dehydration, electrolyte imbalances, and life-threatening complications if not addressed quickly.
Either way, this combination of symptoms deserves close attention because it indicates significant GI upset.
Dog Suddenly Throwing Up and Diarrhea: Common Causes
Dietary Indiscretion
This is the most common cause of sudden vomiting and diarrhea in dogs. Dogs are natural scavengers, and even the most well-behaved pups can get into the trash, eat spoiled leftovers, chew on outdoor debris, or grab a fatty snack.
When this happens, the stomach and intestines react violently, often within hours.
You may see vomiting first, followed by watery diarrhea as the gut tries to clear the irritant. Greasy or rich foods can trigger pancreatitis, which worsens the symptoms quickly.
Because dietary indiscretion ranges from mild stomach upset to serious inflammation, any worsening symptoms or signs of lethargy should not be ignored.
Read more: Dog Suddenly Not Eating and Vomiting (Why it happens)
Viral or Bacterial Infections
Viruses such as parvo, distemper, or canine coronavirus can trigger sudden, severe vomiting and diarrhea.
Parvo in particular causes bloody diarrhea, uncontrollable vomiting, abdominal pain, and rapid dehydration — especially in puppies and unvaccinated dogs.
Bacterial infections (like Salmonella, E. coli, or Campylobacter) can spread through contaminated food, water, or surfaces.
These infections create intense inflammation of the stomach and intestines, resulting in sudden fluid loss and inability to keep anything down.
Because these conditions can spread to other dogs and escalate quickly, early veterinary intervention is crucial.
Intestinal Parasites
Parasites are a frequent cause of sudden gastrointestinal distress. Roundworms, hookworms, whipworms, coccidia, or giardia can trigger vomiting and diarrhea — sometimes with mucus, blood, or a foul odor.
A dog can appear perfectly normal one day and wake up sick the next as parasite numbers multiply.
Even dogs on preventatives can become infected, especially if they drink from puddles, eat feces, or explore contaminated soil.
Because parasites can persist or worsen without treatment, stool testing is essential whenever vomiting and diarrhea occur together.
Toxin Exposure
Household chemicals, toxic plants, medications, moldy food, and human substances like xylitol can cause violent vomiting and explosive diarrhea within minutes to hours of ingestion.
Toxins irritate or damage the stomach lining, disrupt the liver and kidneys, and interfere with normal bodily functions.
You may notice drooling, tremors, pale gums, or weakness alongside GI symptoms.
This is one of the most serious causes because many toxins produce internal damage before symptoms even appear. Immediate veterinary care is critical for suspected toxin exposure.
Pancreatitis
Pancreatitis often strikes suddenly, especially after a dog eats a fatty meal. When the pancreas becomes inflamed, digestive enzymes meant to break down food begin damaging the pancreas itself.
This causes vomiting, diarrhea, hunched posture, fever, belly pain, and refusal to eat.
Because pancreatitis can quickly lead to dehydration and organ dysfunction, it is not a “wait and see” condition.
Senior dogs, overweight dogs, and certain breeds (like Schnauzers) are more at risk.
Stress or Overexcitement
Stress-induced gastrointestinal upset is more common than most owners realize.
Boarding, moving homes, loud noises, vet visits, car rides, or major routine changes can all trigger sudden vomiting and diarrhea.
Stress affects gut motility and the balance of bacteria in the intestines, leading to loose stool and stomach upset.
While stress diarrhea often resolves once the dog calms down, any vomiting that persists requires attention.
Food Allergies and Sudden Food Changes
Changing food too quickly or feeding something your dog is sensitive to can trigger immediate stomach reactions.
Allergies or intolerances cause inflammation along the gut lining, resulting in nausea, vomiting, and soft or watery stool.
If both symptoms appear shortly after introducing a new food, the gut may be rejecting the ingredient.
Related: Dog throwing up and diarrhea (Causes explained)
What to Do If Your Dog Is Suddenly Throwing Up and Has Diarrhea
Start by withholding food for 12 hours if your dog is an adult and otherwise healthy. This gives the stomach time to settle without working harder. Puppies should not fast without veterinary guidance due to low blood sugar risk.
Offer small amounts of water or ice chips frequently to prevent dehydration. If your dog vomits water immediately, this signals a more serious issue.
Once vomiting slows, introduce bland foods such as boiled chicken and rice in small portions. Feed tiny meals throughout the day rather than one large serving.
Keep your dog comfortable, rested, and monitored for changes in energy, gum color, or bathroom habits.
If the cause is mild, symptoms often improve within 24 hours — but worsening signs mean immediate veterinary evaluation.
When to Call or Visit Your Vet
Seek emergency care if your dog:
• Cannot keep water down.
• Has repeated vomiting for more than 12–24 hours.
• Shows bloody diarrhea or black, tarry stool.
• Appears weak, dehydrated, or in pain.
• Has pale or yellow gums.
• Has a swollen belly or difficulty standing.
• Is a puppy, senior, or has a chronic condition.
• May have eaten something toxic.
• Has vomiting and diarrhea at the same time that worsens rapidly.
These symptoms may indicate parvo, pancreatitis, obstruction, toxin ingestion, or organ dysfunction — all requiring immediate veterinary care.
Read more: Dog Suddenly Has Loose Stool (What it means and how to help)
Key Takeaway
When your dog is suddenly throwing up and has diarrhea, it’s almost always a sign that the gut is reacting strongly — either to food, infection, parasites, toxins, or underlying disease.
Mild cases improve with rest, hydration, and a bland diet, but severe or persistent symptoms need veterinary care quickly.
Trust your instincts, monitor your dog closely, and seek professional help anytime dehydration, lethargy, or repeated vomiting appears. Your quick action can make a life-saving difference.