When an older dog suddenly stops eating and develops diarrhea, it’s a red flag that something more serious could be going on.
Appetite loss combined with digestive upset is especially worrying in senior dogs because their bodies are less resilient.
We outline the common causes of loss of appetite and diarrhea in old dogs, what you can do at home, and when to seek veterinary help.
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Old Dog Not Eating and Has Diarrhea — Why It Happens
Loss of appetite paired with diarrhea in senior dogs is usually caused by underlying illness or digestive system disruption. Common causes include gastrointestinal infections, pancreatitis, organ disease, food sensitivities, or even cancer.
In older dogs, changes in metabolism, immune response, and organ function make them more vulnerable to dehydration and nutrient imbalances when diarrhea strikes.
You often notice other signs too — such as vomiting, lethargy, weight loss, or abdominal pain — all of which can point toward a deeper health issue that shouldn’t be ignored.
Old Dog Not Eating and Has Diarrhea: Common Causes
Gastrointestinal Infections
Infections of the stomach or intestines, caused by bacteria, viruses, or parasites, are a frequent reason for appetite loss and diarrhea.
Older dogs may have weaker immune systems, so even mild infections can hit them harder than younger dogs.
You may notice watery or foul-smelling stools, occasional blood or mucus, and a refusal to eat.
If the infection continues unchecked, dehydration and weight loss quickly set in, putting extra strain on your senior dog’s body.
Read more: Old Dog Not Eating and Throwing Up (Here’s why it happens)
Pancreatitis
Pancreatitis, or inflammation of the pancreas, is another serious condition in senior dogs.
When the pancreas becomes inflamed, it releases digestive enzymes prematurely, irritating the stomach and intestines.
This often causes diarrhea, vomiting, abdominal pain, and a sharp decline in appetite.
Pancreatitis can be triggered by fatty meals, obesity, or even certain medications. In older dogs, the risk increases due to cumulative wear on the pancreas over the years. Left untreated, pancreatitis can become life-threatening.
Liver Disease
The liver plays a critical role in digestion, metabolism, and toxin removal. When it isn’t functioning properly, symptoms like diarrhea and appetite loss quickly appear.
Older dogs are more prone to liver disease, whether from age-related decline, infections, or cancer. You might notice yellowing of the eyes or gums, increased thirst, vomiting, and weakness along with the diarrhea. Because the liver is central to so many processes, disease in this organ can escalate quickly.
Kidney Disease
Chronic kidney disease is common in older dogs and often causes both digestive symptoms and loss of appetite.
As toxins build up in the bloodstream, the stomach and intestines become irritated, leading to nausea, diarrhea, and refusal to eat. Dogs with kidney issues may also drink and urinate more, show signs of weakness, and gradually lose weight.
Since the kidneys are vital for filtering waste, untreated kidney disease results in severe illness and is ultimately fatal without management.
Cancer
Unfortunately, cancer is a leading cause of illness in senior dogs. Tumors affecting the digestive system, liver, or other organs can trigger both appetite loss and diarrhea.
In some cases, the cancer itself disrupts digestion. In others, it weakens the immune system or spreads toxins that make your dog feel unwell.
Symptoms often progress slowly at first — diarrhea that doesn’t resolve, gradual weight loss, reluctance to eat, and increased fatigue.
Because cancer in dogs can look similar to other conditions, veterinary diagnostics like bloodwork, X-rays, or ultrasounds are essential for identifying it.
Dietary Indiscretion or Food Sensitivity
Not every case is life-threatening — sometimes a senior dog eats something their stomach can’t handle.
Trash, spoiled food, or a sudden change in diet may upset the digestive system, leading to diarrhea and loss of appetite.
However, while younger dogs often bounce back quickly, older dogs may struggle to recover, especially if dehydration sets in.
Some seniors also develop food intolerances over time, reacting poorly to certain proteins or additives.
Chronic diarrhea paired with reluctance to eat could signal a dietary issue that needs veterinary guidance.
What to Do If Your Old Dog Is Not Eating and Has Diarrhea
At home, the most important thing is to prevent dehydration and give your dog’s digestive system time to rest.
Encourage water intake frequently, offering small sips or even ice cubes if they’re reluctant to drink. Some owners find that offering low-sodium chicken broth can tempt a senior dog to rehydrate.
Withhold food for 12–24 hours (unless your vet has advised otherwise) to allow the stomach and intestines to settle. Afterward, you can offer a bland diet of plain boiled chicken and rice in small portions.
If your dog shows interest, stick to smaller, more frequent meals to avoid overwhelming the digestive system. Keep their environment calm and comfortable, as stress can worsen diarrhea and appetite loss.
It’s also helpful to monitor stool consistency, color, and frequency, since this information will guide your veterinarian in identifying the underlying cause.
When to Call or Visit Your Vet
In older dogs, diarrhea and refusal to eat are never symptoms to brush off.
You should call your vet immediately if the diarrhea is watery, bloody, or lasts more than 24 hours. Loss of appetite beyond a single skipped meal in a senior dog is also concerning and warrants professional evaluation.
Seek urgent care if your dog is vomiting in addition to diarrhea, showing signs of abdominal pain (whining, hunching, reluctance to move), or seems unusually weak or lethargic.
Other red flags include pale or yellow gums, rapid weight loss, refusal to drink water, or signs of dehydration like sunken eyes and skin that doesn’t quickly return to place when pinched.
Because senior dogs decline quickly, even mild symptoms can escalate fast — it’s always better to have your veterinarian examine your dog sooner rather than later.
Read more: Old Dog Not Eating (Causes and what to do)
Key Takeaway
When an old dog is not eating and has diarrhea, it’s often a sign of something more serious than a simple stomach upset. From infections and pancreatitis to organ disease or cancer, the causes can range from mild to life-threatening.
At home, you can offer fluids, rest, and a bland diet, but veterinary guidance is essential if symptoms last longer than a day or are accompanied by other concerning signs.
Your senior dog relies on you to notice these changes and act quickly. With timely care, many of the conditions causing diarrhea and appetite loss can be managed, giving your dog comfort and more happy years by your side.