When your dog has loose stool and seems unusually thirsty, it’s often a sign that their body is struggling to stay hydrated and may be fighting off an internal imbalance.
These two symptoms—digestive upset and increased thirst—are closely linked because the fluid loss from diarrhea or loose stool triggers your dog’s natural instinct to drink more water.
We outline the common reasons behind loose stool and excessive drinking in dogs, what this combination of symptoms means for your dog’s health, and when to seek veterinary help before dehydration or serious illness sets in.
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Dog Loose Stool and Drinking Lots of Water: What It Means
A dog having loose stool and drinking lots of water can be caused by dietary changes, infection, intestinal inflammation, metabolic disorders, medications, or heat-related dehydration. While some causes are mild, others may signal chronic disease or organ stress that needs prompt attention.
Dog Loose Stool and Drinking Lots of Water: Common Causes
Dietary Indiscretion or Sudden Food Change
If your dog’s digestive system is upset from eating something unusual—like table scraps, garbage, or a sudden new brand of food—loose stool is the first sign.
When this happens, water loss through diarrhea stimulates the thirst response, making your dog drink excessively to replenish lost fluids.
The intestines can’t absorb water properly when irritated, so even with increased drinking, dehydration may still occur. In mild cases, symptoms improve within a day or two once the offending food passes.
However, persistent watery stool and constant thirst may indicate more serious intestinal irritation or infection.
Transitioning to new foods gradually—over 7 to 10 days—helps prevent this common cause of digestive upset.
Read more: Dog Loose Stool and Vomiting (Digestive upset and dehydration risks)
Bacterial or Viral Infection
Infections in the gut can trigger both loose stool and excessive drinking. Bacteria like Salmonella and Campylobacter or viruses such as parvovirus and coronavirus inflame the intestinal lining, preventing normal fluid absorption.
As the intestines secrete more fluid to flush out pathogens, the dog’s body compensates by drinking more water to avoid dehydration. You may also notice vomiting, fever, lethargy, and loss of appetite.
Puppies and senior dogs are particularly vulnerable because their immune systems are weaker and can’t recover fluid balance as easily. If diarrhea and thirst persist longer than 24 hours or stool appears bloody, veterinary testing is needed to identify the infection and start supportive care.
Intestinal Parasites
Parasites such as hookworms, whipworms, giardia, or coccidia irritate the intestines, leading to chronic loose stool. These organisms consume nutrients and cause inflammation, preventing the body from absorbing water effectively.
As fluid is lost through stool, your dog compensates by drinking more. In some cases, stool may contain mucus, appear greasy, or smell unusually foul. You might also see signs like a bloated belly, scooting, or unexplained weight loss.
Your veterinarian can confirm parasites with a fecal exam and prescribe the right deworming or antiparasitic medication. Keeping your dog on a regular deworming schedule and avoiding stagnant water or contaminated soil reduces reinfection risk.
Food Intolerances and Allergies
Dogs can be sensitive to specific ingredients like chicken, beef, dairy, soy, or grains. When they consume an allergen, the immune system reacts by inflaming the gut lining. This inflammation disrupts water absorption and triggers loose stool, often accompanied by gas, itching, or ear infections.
Because inflammation leads to water loss, affected dogs may drink more to rehydrate. Chronic loose stool and excessive thirst caused by diet-related inflammation often improve once the offending ingredient is removed.
If you suspect food intolerance, a vet-guided elimination diet using novel or hydrolyzed protein sources can help pinpoint the trigger and restore digestive balance.
Heat and Dehydration
Hot weather or excessive physical activity can make dogs drink more water, but when combined with loose stool, it can quickly lead to dehydration. As the body loses fluids through diarrhea, the natural response is to increase drinking to compensate.
However, when dehydration progresses too quickly, even constant water intake can’t keep up with fluid loss. Early signs include dry gums, sunken eyes, and lethargy. Left untreated, heat-related dehydration can become an emergency.
Always ensure your dog has access to fresh, cool water, especially during hot weather or after exercise. If your dog continues to have loose stool while drinking heavily, it’s best to see your vet to rule out underlying infection or organ stress.
Pancreatitis
Pancreatitis—an inflammation of the pancreas—is a common cause of digestive distress accompanied by increased thirst. When the pancreas becomes inflamed, it releases digestive enzymes prematurely, causing pain, vomiting, and diarrhea.
Because fluid loss occurs through stool and vomiting, affected dogs often drink large amounts of water to compensate. You might notice your dog hunching their back, refusing food, or showing signs of abdominal discomfort.
Pancreatitis is often triggered by high-fat meals or sudden indulgence in greasy foods. It’s especially common in small breeds such as Miniature Schnauzers and Yorkshire Terriers. Prompt veterinary care is essential, as dehydration and organ damage can develop rapidly.
Metabolic Diseases
When excessive thirst accompanies loose stool, metabolic diseases like kidney or liver dysfunction should also be considered. In kidney disease, the kidneys fail to retain water efficiently, leading to increased urination and thirst. The buildup of waste in the body can cause nausea and diarrhea.
Liver disease interferes with bile production, which can result in loose, pale-colored stool and vomiting. Both conditions make dogs drink excessively as the body attempts to flush toxins through urine.
Older dogs are particularly prone to these metabolic issues. Bloodwork and urinalysis help identify the root cause and guide appropriate treatment.
Medications or Antibiotics
Some medications, particularly antibiotics or steroids, can upset the intestinal balance of bacteria and cause loose stool. When this occurs, dogs may start drinking more to rehydrate from the resulting fluid loss.
Antibiotics, while useful for fighting infections, also disrupt beneficial gut flora, leading to temporary diarrhea. Adding probiotics or a bland diet during and after antibiotic use can help restore digestive balance.
If your dog’s excessive thirst or loose stool persists after finishing medication, consult your vet—dosage adjustments or additional treatments may be needed.
Cushing’s Disease
Cushing’s disease (hyperadrenocorticism) causes the adrenal glands to produce excess cortisol, a hormone that affects metabolism, thirst, and digestion. Dogs with Cushing’s often drink excessively, urinate frequently, and may experience intermittent loose stool due to hormonal imbalance.
Other common signs include hair loss, pot-bellied appearance, and panting. Since the condition progresses gradually, many owners first notice increased drinking and changes in bowel habits. A veterinarian can diagnose Cushing’s with blood and urine tests and manage it through medication or surgery, depending on severity.
Read more: Dog Loose Stool with No Other Symptoms (What it means)
What to Do if Your Dog Has Loose Stool and Is Drinking Lots of Water
If your dog’s symptoms are mild and they otherwise seem alert, you can start with home care for 12–24 hours. Offer plenty of clean, fresh water, but remove food for 8–10 hours to allow the digestive system to rest.
After the fasting period, reintroduce small portions of a bland diet such as boiled chicken and rice. Feed small, frequent meals and monitor if the stool begins to firm up. Gradually transition back to regular food over several days once improvement is steady.
Avoid giving flavored electrolyte drinks unless advised by your vet—plain water is safest for most dogs.
Keep an eye on hydration by checking gum moisture and skin elasticity. Gently lift the skin at the back of the neck—if it doesn’t quickly spring back, dehydration may be setting in.
If your dog continues to have loose stool, shows signs of pain, vomits repeatedly, or drinks excessively for more than a day, contact your veterinarian for diagnostic testing and supportive treatment.
When to Call or Visit the Vet
Call your vet immediately if your dog:
• Has loose stool lasting more than 24–36 hours.
• Drinks excessively but still seems lethargic or weak.
• Vomits repeatedly or refuses food and water
• Has blood or black tarry stool.
• Shows signs of dehydration (dry gums, sunken eyes, tented skin).
• Produces very little or no urine despite drinking heavily.
• Has a history of pancreatitis, diabetes, or kidney disease.
• Is a puppy, senior, or has an underlying chronic condition.
Emergency care is needed if your dog collapses, can’t keep water down, or shows signs of severe dehydration or bloating.
Read more: Dog Soft Stool and Not Eating (What it means)
Key Takeaway
Dog loose stool and drinking lots of water is your dog’s way of signaling distress in the digestive or metabolic system. While mild cases can result from diet changes or mild infections, persistent symptoms may indicate organ dysfunction or hormonal imbalance.
Hydration is crucial—but so is finding the underlying cause. With prompt care, a balanced diet, and veterinary guidance, most dogs recover quickly and return to their happy, healthy selves.