When an older dog suddenly starts vomiting and having diarrhea, it’s deeply worrying. These symptoms can quickly lead to dehydration and signal anything from a mild stomach upset to a serious medical condition.
We outline the common causes of vomiting and diarrhea in old dogs, what you can do at home, and when to seek veterinary help.
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Old Dog Throwing Up and Diarrhea — Why It Happens
Vomiting and diarrhea in old dogs usually occur when the digestive system becomes irritated or inflamed. This may be caused by infections, toxins, diet changes, or underlying organ disease. Older dogs have weaker immune systems and slower metabolism, making it harder for their bodies to recover from even mild gastrointestinal distress.
Sometimes, both symptoms appear together because whatever irritates the stomach also affects the intestines.
While mild cases may resolve with rest and a bland diet, persistent vomiting and diarrhea in an elderly dog can quickly turn dangerous.
Old Dog Throwing Up and Diarrhea: Common Causes
Dietary Indiscretion or Sudden Diet Change
One of the most frequent causes of vomiting and diarrhea in old dogs is dietary indiscretion — eating something they shouldn’t.
Garbage, spoiled food, rich table scraps, or even a sudden switch in kibble can irritate a senior dog’s sensitive stomach and intestines. Because aging dogs have slower digestion, even small dietary changes can trigger major upsets.
You might see vomiting soon after eating and watery stools within hours. If your dog only has mild symptoms and is otherwise alert, resting the stomach for a short period can help — but continued symptoms warrant a vet check.
Read more: Old Dog Diarrhea and Dying (When to worry and how to comfort them)
Infections (Bacterial or Viral)
Bacterial infections like Salmonella or Clostridium and viral infections such as parvovirus or coronavirus can lead to severe vomiting and diarrhea.
These pathogens inflame the stomach and intestines, causing the body to expel food and fluid rapidly. In older dogs, immune defenses are weaker, so infections can escalate quickly, leading to blood in the stool, fever, or extreme lethargy.
Because dehydration develops rapidly, any senior dog showing these symptoms needs prompt veterinary care. Blood tests and stool samples help confirm the diagnosis and guide treatment.
Pancreatitis
Pancreatitis — inflammation of the pancreas — is a leading cause of vomiting and diarrhea in older dogs, particularly those fed fatty foods.
The pancreas releases digestive enzymes, but when it becomes inflamed, these enzymes start digesting the pancreas itself, causing pain and digestive upset.
You might notice your dog vomiting repeatedly, refusing food, hunching their back in pain, or passing greasy, foul-smelling diarrhea. Pancreatitis can range from mild to life-threatening, so it’s critical to have your vet assess your dog if you suspect it.
Kidney or Liver Disease
Both the liver and kidneys play essential roles in filtering toxins from the body. When they begin to fail — a common issue in older dogs — toxins can accumulate in the bloodstream, leading to nausea, vomiting, and diarrhea.
Dogs with kidney or liver disease often show additional signs like bad breath, increased thirst, weight loss, or yellow-tinted eyes and gums.
These conditions require medical management and supportive care. If your dog has a history of organ issues, any digestive upset should be treated as potentially serious.
Intestinal Parasites
Parasites such as roundworms, hookworms, or Giardia can affect dogs of any age, but seniors are especially vulnerable due to weaker immunity.
These parasites damage the intestinal lining, leading to vomiting, diarrhea, and weight loss. Sometimes, you may even see worms in your dog’s stool or vomit.
Chronic parasite infections can cause malnutrition and anemia in old dogs, so regular fecal exams and deworming are essential even for senior pets that stay indoors.
Cancer or Gastrointestinal Tumors
Unfortunately, vomiting and diarrhea can also indicate cancer in older dogs, especially tumors in the stomach, intestines, or other digestive organs.
Cancers can interfere with digestion and cause internal bleeding, leading to dark or tarry stools, frequent vomiting, and appetite loss. Weight loss and weakness often follow as the disease progresses.
Not all vomiting or diarrhea means cancer, but it’s an important rule-out — especially when symptoms are chronic, severe, or accompanied by other changes in behavior or appearance.
Read more: Old Dog Bloody Diarrhea (What it means and what to do)
What to Do If Your Old Dog Is Throwing Up and Has Diarrhea
If your old dog suddenly develops vomiting and diarrhea, stay calm but act quickly. Start by withholding food for 12–24 hours (but never water) to let the digestive tract settle. Offer small amounts of water or ice cubes frequently to prevent dehydration.
Once vomiting has stopped for several hours, begin a bland diet such as boiled chicken and plain rice or cooked pumpkin and white fish. Feed small portions every few hours and monitor stool consistency.
If your dog tolerates food well after 24–48 hours, slowly transition back to their normal diet. You can also discuss adding a probiotic supplement with your vet to restore gut balance.
Avoid giving over-the-counter human medications like Pepto-Bismol or Imodium unless specifically prescribed. These can be harmful to dogs, especially seniors.
Keep your dog in a quiet, comfortable area and monitor for new symptoms such as bloody stool, weakness, or continued vomiting.
When to Call or Visit Your Vet
Vomiting and diarrhea can quickly dehydrate an old dog — a medical emergency in itself.
You should call your vet immediately if your dog’s vomit or stool contains blood, they refuse to eat or drink for more than 24 hours, or they appear weak, shaky, or in pain.
Also seek urgent care if the diarrhea becomes watery or black and tarry, as this can signal internal bleeding. Dogs with known kidney, liver, or heart disease should never be left untreated when vomiting or diarrhea appear.
Even if your dog seems better after a day or two, ongoing mild digestive upset can still mean something deeper — such as an infection or early organ dysfunction. A vet exam ensures your dog receives fluids, medications, and the right diet adjustments to recover safely.
Related: Old dog constant diarrhea (Causes and when to worry)
Key Takeaway
Vomiting and diarrhea in an old dog can range from a mild stomach upset to a serious health crisis. Because older dogs are more prone to dehydration and organ problems, it’s best to monitor closely and act early.
If your dog is alert, drinking water, and symptoms are brief, gentle care at home can help. But if the vomiting or diarrhea persists beyond a day, or your dog becomes weak, dehydrated, or uninterested in food, call your vet right away.
Prompt attention, hydration, and careful diet management can often make the difference between a quick recovery and a worsening condition. With your care and your vet’s guidance, your old friend can regain comfort and stability faster.