It’s always distressing to see your dog feeling unwell and suffering from diarrhea. Whether it happens suddenly or lingers for days, these symptoms can indicate anything from a simple stomach upset to a more serious health concern.
We outline the common causes of sickness and diarrhea in dogs, what you can do at home, and when to seek veterinary help.
Dog Sick Diarrhea — Why It Happens
A dog that’s sick and has diarrhea is often dealing with irritation or inflammation in the digestive tract. This can stem from eating something inappropriate, infections, parasites, or even underlying diseases like pancreatitis or kidney problems.
While some cases clear up within 24 hours, persistent or severe diarrhea can quickly lead to dehydration — making it vital to identify the cause early and act fast.
Dog Sick, Diarrhea: Common Causes
1. Dietary Indiscretion (Eating Something They Shouldn’t)
One of the most common reasons dogs get sick and develop diarrhea is dietary indiscretion — a fancy way of saying they’ve eaten something they shouldn’t.
Dogs are curious by nature, and rummaging through trash, eating spoiled food, or swallowing foreign objects is not unusual.
When this happens, their stomach and intestines become irritated, leading to vomiting, loose stools, and loss of appetite.
You might notice your dog licking their lips, drooling, or straining to poop. The diarrhea may have pieces of food or mucus, depending on what was ingested.
Most mild cases improve with rest and a temporary bland diet, but if your dog continues vomiting, appears weak, or passes blood, this can signal something more serious — like a blockage or toxin ingestion — and requires veterinary attention immediately.
Read more: Dog Sick Diarrhea and Not Eating (What it means and when to worry)
2. Bacterial or Viral Infections
Infections are another frequent culprit behind sickness and diarrhea. Bacteria such as Salmonella or E. coli, and viruses like parvovirus or coronavirus, can inflame the gut, leading to severe diarrhea and vomiting.
Parvovirus, in particular, is extremely dangerous for puppies and unvaccinated dogs. It causes bloody diarrhea, dehydration, and extreme weakness that can turn fatal within days without treatment.
Even mild infections can drain your dog’s energy and appetite. Because bacteria and viruses are often contagious, your vet will likely recommend isolation, stool testing, and supportive care to prevent spread and aid recovery.
3. Parasites
Intestinal parasites such as roundworms, hookworms, whipworms, and giardia are a leading cause of chronic diarrhea in dogs. These parasites damage the intestinal lining, interfere with nutrient absorption, and can cause vomiting, poor coat quality, and weight loss.
Puppies, rescue dogs, and those in boarding environments are especially vulnerable. Giardia, a microscopic parasite found in contaminated water, often leads to greasy or foul-smelling diarrhea that may come and go.
If your dog’s diarrhea keeps returning, your vet may request a fecal exam to check for parasites. Routine deworming and hygiene are essential in preventing reinfection — especially in multi-dog households.
4. Pancreatitis
Pancreatitis, or inflammation of the pancreas, is a painful and potentially serious condition often triggered by eating fatty or greasy foods. When the pancreas becomes inflamed, it releases digestive enzymes prematurely, essentially “digesting” parts of the dog’s own organs.
Symptoms include vomiting, diarrhea, hunched posture, belly pain, and fatigue. The diarrhea may be greasy, yellowish, or foul-smelling.
Pancreatitis can escalate quickly and requires prompt veterinary care. Dogs often need hospitalization for IV fluids, anti-nausea medication, and a strict low-fat diet during recovery. Left untreated, it can cause lasting organ damage or even death.
5. Food Allergies or Intolerances
Just like humans, dogs can develop sensitivities to certain ingredients in their food. Common allergens include beef, chicken, dairy, wheat, and soy. When your dog eats a trigger food, their immune system reacts, causing inflammation in the gut and resulting in diarrhea, vomiting, or even itchy skin and ear infections.
If you notice your dog getting sick after certain meals, a hypoallergenic elimination diet under your vet’s guidance can help identify the offending ingredient.
Switching to a limited-ingredient or prescription digestive diet can often bring fast relief and prevent future flare-ups.
6. Toxins and Poisoning
Household items like chocolate, xylitol (found in sugar-free gum), grapes, certain plants, and human medications can all cause sudden sickness and diarrhea in dogs. These toxins irritate the stomach and can also affect the liver, kidneys, or nervous system.
A poisoned dog may drool excessively, tremble, vomit repeatedly, or have bloody diarrhea. Time is critical — don’t wait to “see if it passes.”
Call your vet or an emergency poison helpline immediately. Bring the packaging or a sample of what your dog ingested to the clinic for accurate treatment.
7. Stress or Sudden Change in Environment
Dogs can also develop diarrhea when stressed — for example, after moving homes, boarding, or loud events. Stress hormones affect the digestive system, speeding up intestinal movement and reducing water absorption.
This type of diarrhea is usually short-lived but can still cause fatigue and dehydration if it continues. Calm reassurance, consistent feeding times, and quiet rest often help your dog’s stomach settle.
8. Underlying Diseases (Kidney, Liver, or Addison’s Disease)
Sometimes, diarrhea and sickness point to a deeper health problem. Dogs with liver disease, kidney failure, or Addison’s disease (a hormone disorder) can all show similar signs.
These conditions interfere with metabolism and toxin removal, leading to nausea, vomiting, and diarrhea. Chronic cases may also show symptoms like increased thirst, weight loss, or changes in urine color.
Bloodwork and imaging are needed for diagnosis, but early detection dramatically improves management and your dog’s comfort.
Read more: Dog Sick Diarrhea Blood (Find out the causes)
What to Do If Your Dog Is Sick and Has Diarrhea
If your dog has mild diarrhea but is otherwise bright and alert, you can start by managing it at home.
Keep your dog hydrated by offering small amounts of water every hour. If they refuse plain water, try low-sodium chicken broth or an electrolyte solution recommended by your vet.
Withhold food for about 12 hours to give the stomach a break, then reintroduce a bland diet of boiled chicken and rice in small portions. Continue for 24–48 hours, watching for signs of improvement such as firmer stools or better energy.
Avoid giving over-the-counter human medications unless specifically approved by your vet — some can worsen your dog’s condition or cause toxicity.
Ensure your dog has a quiet, comfortable space to rest. Stress can worsen diarrhea, so keeping them calm helps recovery.
If you recently changed your dog’s food, revert to their old diet and make future transitions gradually over 7–10 days to prevent stomach upset.
If your dog’s condition doesn’t improve within 48 hours or they start vomiting persistently, seek veterinary care right away.
When to Call or Visit Your Vet
Call your vet immediately if you notice:
Blood in the stool or vomit
Repeated vomiting with refusal to drink or eat
Signs of dehydration (dry gums, sunken eyes, skin that stays “tented” when pinched)
Weakness, collapse, or shaking
Diarrhea lasting longer than two days
Puppies, small breeds, and older dogs dehydrate faster and are at higher risk for complications, so don’t delay treatment.
Your vet will perform a physical exam, run blood tests, or analyze stool samples to pinpoint the cause. In many cases, simple supportive care — like fluids, anti-nausea medication, or probiotics — can help your dog recover quickly.
More serious cases, such as pancreatitis or parvovirus, require hospitalization and intensive treatment. Acting early can make all the difference.
Read more: Dog Pooping Blood After Diarrhea (When to go to the vet)
Key Takeaway
A dog that’s sick and has diarrhea is experiencing distress in their digestive system — but the causes range widely, from mild dietary upsets to infections or organ disease.
Always monitor your dog’s energy, hydration, and stool consistency closely. Mild cases may settle with rest, hydration, and a bland diet, but worsening or prolonged diarrhea demands professional care.
Your vet can identify the underlying cause, relieve discomfort, and prevent complications from dehydration.
With timely attention and supportive care, most dogs bounce back to their playful, happy selves in no time.