When your dog is suddenly vomiting and has diarrhea at the same time, it can be alarming and confusing.
These symptoms can come on quickly, worsen fast, and leave your dog feeling weak or dehydrated.
This guide explains the most common causes of sudden vomiting and diarrhea in dogs, what you can do at home, and when it’s best to involve your veterinarian.
Dog Suddenly Vomiting and Diarrhea: Why It Happens
A dog suddenly vomiting and experiencing diarrhea usually means the stomach and intestines are reacting to irritation, infection, inflammation, or something your dog has eaten. These symptoms often occur together because both the stomach and intestines are affected at the same time, which can happen with dietary indiscretion, viral illnesses, bacterial infections, parasites, or exposure to toxins.
Many dogs show these signs after eating something unusual, while others may develop them due to underlying medical issues that need urgent attention.
Sudden digestive upset is the body’s way of rapidly clearing harmful substances, but it can quickly lead to dehydration if not treated promptly.
Dog Suddenly Vomiting and Diarrhea: Common Causes
Dietary Indiscretion
Dogs are notorious for getting into the trash, eating table scraps, or swallowing things they shouldn’t. When a dog suddenly vomits and has diarrhea, one of the most common culprits is dietary indiscretion.
Eating spoiled food, fatty leftovers, or foreign objects irritates the stomach and intestines immediately. This irritation triggers vomiting as the body tries to eject the offending material, while diarrhea develops as the intestines rapidly push contents through to eliminate toxins.
You may also notice abdominal gurgling, gas, drooling, pacing, or restlessness. While this cause is often mild, it can still lead to dehydration quickly, especially in small dogs.
Related: Dog suddenly not eating and vomiting (Causes explained)
Viral Infections
Viral diseases—especially parvovirus—are some of the most serious causes of sudden vomiting and diarrhea in dogs. These viruses attack the intestinal lining, causing severe inflammation and sloughing of the tissue responsible for nutrient absorption.
This results in sudden, relentless vomiting, watery or bloody diarrhea, lethargy, and rapid dehydration. Puppies and unvaccinated dogs are at highest risk, but any dog can become infected.
Because these viruses progress quickly and can be fatal without treatment, they are considered medical emergencies. If your dog’s symptoms are explosive, bloody, or accompanied by severe weakness, a viral infection must be ruled out immediately.
Bacterial Infections
Dogs can develop acute vomiting and diarrhea after exposure to harmful bacteria in contaminated food, water, or animal feces. These bacteria damage the intestinal lining and trigger rapid fluid loss.
Bacterial infections often cause vomiting and diarrhea that may be foul-smelling, slimy, or streaked with mucus. Fever is common, and dogs may show decreased appetite or appear painful when touched around the abdomen.
These infections need prompt veterinary care because dogs can become dehydrated within hours, and some bacteria can even be transmitted to humans.
Parasites
Intestinal parasites can cause sudden or worsening vomiting and diarrhea, especially when present in large numbers or when a dog’s immune system becomes compromised.
Giardia, one of the most common parasites, frequently causes watery diarrhea, nausea, gas, and intermittent vomiting. Worms such as roundworms or hookworms can irritate the intestines enough to cause sudden digestive distress.
Dogs with parasite-related vomiting and diarrhea may lose weight, have a dull coat, or strain during bowel movements. Puppies are especially vulnerable because their small bodies cannot tolerate rapid fluid loss.
Toxin Exposure
Many toxins—such as certain human medications, poisonous plants, household chemicals, or toxic foods like grapes and xylitol—cause immediate vomiting and diarrhea in dogs.
The gastrointestinal system attempts to eliminate the toxin quickly, which explains the sudden onset of both symptoms. But toxins can also affect the liver, kidneys, and nervous system, leading to tremors, drooling, unsteadiness, or collapse.
Because many toxic substances become more dangerous the longer they stay in the body, any suspicion of toxin exposure should be treated as an emergency.
Pancreatitis
Pancreatitis causes inflammation of the pancreas, often triggered by eating fatty foods. When the pancreas becomes inflamed, it releases digestive enzymes prematurely, which irritate both the stomach and intestines.
This leads to vomiting, diarrhea, abdominal pain, and weakness. Dogs with pancreatitis may adopt a “prayer position,” where they stretch their front legs forward and lower their chest to the ground.
This condition is extremely painful and can become life-threatening if untreated, especially when vomiting and diarrhea occur together.
Related: Dog Suddenly Vomiting Yellow (Why it happens)
What to Do If Your Dog Is Suddenly Vomiting and Has Diarrhea
When your dog suddenly develops vomiting and diarrhea, one of the first steps is to keep them comfortable and monitor their hydration.
Offer small sips of water frequently, but avoid allowing them to drink large amounts at once, which can trigger more vomiting. If your dog refuses water or vomits it back up, dehydration can escalate quickly.
Withhold food for several hours to allow the stomach to settle, unless your dog is a small breed or puppy who is prone to low blood sugar. When reintroducing food, start with a bland diet such as boiled chicken and rice in small, frequent meals. This gives the digestive system a chance to heal gently.
Allow your dog to rest in a calm, quiet environment. Avoid exercise, excitement, or long walks until the stomach stabilizes. Stress can worsen vomiting and diarrhea, so creating a peaceful recovery space is important.
If you have recently changed your dog’s diet or introduced new treats, remove them for now. Sudden dietary changes commonly trigger digestive upset, and simplifying the diet can help determine whether food triggered the symptoms.
Finally, monitor your dog’s stool, vomit, and overall behavior. If vomiting or diarrhea worsens, becomes bloody, or is accompanied by lethargy, refusing food, or collapse, veterinary care is needed right away.
These symptoms progress quickly, and early treatment prevents complications such as severe dehydration or electrolyte imbalances.
When to Call or Visit Your Vet
Seek urgent veterinary care if your dog cannot keep water down, as persistent vomiting can lead to dehydration in a matter of hours. If your dog’s diarrhea becomes watery, bloody, or explosive, this is another sign that medical attention is needed.
Dogs who are extremely lethargic, weak, or unable to stand should be seen immediately. These symptoms may indicate infection, toxin exposure, pancreatitis, or other serious conditions.
If your dog has a fever, swollen abdomen, or appears to be in pain when you touch the belly, go to the vet as soon as possible. Abdominal discomfort combined with vomiting and diarrhea can be a sign of pancreatitis or gastrointestinal obstruction.
Puppies, seniors, and dogs with chronic health issues like diabetes or kidney disease should always be evaluated promptly because they are more vulnerable to fluid loss.
If you suspect your dog ate something toxic—such as human medication, poisonous food, or a household chemical—seek veterinary help right away. Time is critical when dealing with toxins.
Read more: Dog Suddenly Vomiting White Foam (What it means)
Key Takeaway
Sudden vomiting and diarrhea in dogs can range from mild digestive upset to serious medical emergencies. Because these symptoms cause rapid fluid loss, prompt attention is essential.
Start with gentle home care, monitor your dog closely, and seek veterinary help if symptoms worsen or your dog appears weak, dehydrated, or in pain.
With quick action and proper care, most dogs recover well and return to their normal happy selves.