My Dog Is Losing Weight And Drinking Lots Of Water: Why?

My dog is losing weight and drinking lots of water – that might throw any pet parent in panic since any unusual signs in your pet can be concerning.

Here, you can discover why your four-legged companion is shedding pounds and constantly thirsty. Follow up to find the solutions!

18 Reasons Why My Dog Is Losing Weight And Drinking Lots Of Water

my dog is losing weight and drinking lots of water

Inflammatory bowel disease, intestinal parasites, or exocrine pancreatic insufficiency can lead to a decreased appetite and extreme weight loss.

Additionally, your dog may have hormonal imbalances affecting their metabolic demands and experience frequent thirst and urination due to kidney issues.

Here are all the reasons that can explain why your dog lost a lot of weight and drank a lot of water.

Low-quality Diet

My dog lost a lot of weight fast. Why? When body weight starts dropping in dogs, a low-quality diet may be the culprit.

Inadequate nutrition can cause weight loss & increased thirst.

Worms & Parasites

Why is my dog eating but losing weight? Worms & parasites can stand behind that situation as they steal essential nutrients.

Your furry friend might also drink more water to combat dehydration brought by these pesky intruders.

Dental Problems

Neglect dental care, and dental issues will surely follow. Dental probelms leave discomfort & pain in the mouth. From that, dogs can not eat or drink properly.

To compensate for this difficulty, the dog may drink more water to soothe their mouth and stay hydrated. As a result, it causes weight loss and excessive thirst.

Diabetes Mellitus

Diabetes mellitus affects dogs by triggering their thirst due to elevated blood sugar levels. Despite drinking more, they still experience weight loss.


Another the reason for a dog losing weight and not eating can be an early sign of cancer in dogs. Alongside this, they might consume more water.

Diet Changes

Sudden diet changes can disrupt a dog’s digestive system.

Consequently, gastrointestinal issues, such as diarrhea, vomiting, or constipation will arise, as the dog’s digestive system struggles to adapt.

This can result in increased thirst & weight loss. 

Gastrointestinal disorders

A dog lost weight and not eating might be because of gastrointestinal disorders, which also make your pooch crave more water.

For instance, Inflammatory Bowel Disease (IBD) and Gastric Ulcers can cause discomfort and reduce appetite.

Dogs may drink more water to ease their stomachs while shedding pounds. In my experience, when dogs vomit stones, it might suggest an association with IBD.

Heart Disease

Why is my dog losing weight even though he is eating? Heart disease can be to blame.

Dogs with heart disease often exhibit these symptoms due to poor circulation and fluid buildup.

Kidney Disease

In case of a dog eating but losing weight rapidly, kidney disease may be the cause. Damaged kidneys struggle to remove waste, making your dog thirsty.

Weight loss occurs as the body loses essential nutrients.

Liver Disease

Liver problems can be linked to weight loss and increased thirst in dogs. The liver’s inability to function properly affects digestion and nutrient absorption.

That is why your furry friend tends to shed pounds and crave more water.

Metabolic Disorders/Hyperthyroidism

Conditions like hyperthyroidism can speed up a dog’s metabolism. From that, your pet experiences weight loss.

The increased metabolic rate also makes your dog feel thirstier than usual. As said, your dog is dehydrated and needs water intake.

Stress & Anxiety

If you see your dog losing weight and hair but eating, check for signs of stress & anxiety. Stress affects appetite and digestion and can trigger excessive grooming.

Consequently, your dog experiences hair loss. Dogs may also eat less and digest poorly due to the physical and hormonal responses to stress.


Female dogs can lose weight and drink more water during pregnancy or nursing.

The extra energy needed for puppies and hormonal changes can result in weight loss, while nursing increases thirst.

Nasal Problems

Nasal issues can make your pooch lose weight and drink more water.

Difficulty breathing through the nose while eating can steer your dog from food, and mouth breathing can heighten its thirst.

Exocrine Pancreatic Insufficiency

Exocrine pancreatic insufficiency or EPI occurs when the pancreas doesn’t produce enough digestive enzymes.

These enzymes are crucial for breaking down food into nutrients. Without them, dogs can’t absorb nutrients effectively, thereby losing weight.

In addition, when food isn’t properly digested, and nutrients aren’t absorbed, the body may signal increased water intake as to compensate for the loss and stay hydrated.


A dog losing weight but eating can be due to infections, especially in the urinary tract. This issue can cause increased thirst and a decreased appetite.

That is why your pet lost weight.

Addison’s Disease

Addison’s disease, or hypoadrenocorticism, impacts the adrenal glands. These glands regulate crucial functions like metabolism, electrolyte balance, and stress response.

When they malfunction, it disrupts your dog’s health.

Weight loss occurs as the body’s systems become imbalanced, and excessive thirst results from electrolyte disturbances caused by adrenal insufficiency.

Neurologic Conditions

Certain neurological conditions can influence a dog’s eating and drinking patterns.

Conditions affecting the brain or nerves can entail behavioral changes, such as decreased appetite or increased thirst. 

These changes can result in weight loss as the dog’s normal eating habits are disrupted, and altered drinking habits are to be expected due to the neurological condition’s impact on the body’s regulatory systems.

What Should We Do?

dog lost a lot of weight

Monitor Their Weight: Keep an eye on your dog’s weight. While slight weight fluctuations may not be alarming, substantial or rapid weight loss should be a red flag.

Observe for Symptoms: Pay attention to any signs of illness. Consult a veterinarian if your dog displays symptoms like vomiting, lethargy, diarrhea, or increased thirst and urination.

Consider Age: For puppies, any weight loss is a cause for concern, as they should gain weight as they grow.

In older dogs, weight loss can signal underlying health issues, especially chronic kidney disease.

Ensure Proper Nutrition: Address the loss of appetite by providing a well-balanced diet tailored to your dog’s needs.

Specialized diets may sometimes be recommended, such as for dogs with kidney disease.

Maintain Hydration: Ensure your dog has access to clean water.

Abnormal water consumption can indicate various health issues, so monitor their water intake and check their water bowl regularly.

Regular Deworming: Properly deworming your dog helps eliminate worms and parasites. It ensures that your pet can absorb food more effectively.

That is the way to promote their overall health and well-being.

Seek Veterinary Advice: Consult a vet if your dog experiences significant or unexplained weight loss.

Your veterinarian can conduct diagnostic testing to determine the cause and develop a treatment plan.

Regular Vet Visits: Schedule routine check-ups with your veterinarian to assess your dog’s body condition score, discuss any common symptoms, and address concerns promptly.

Should I Be Worried If My Dog Is Drinking More Water Than Usual?

Generally no. If your dog drinks more water than usual, it might not always be a cause for concern.

Dogs may have increased thirst for various reasons, including excessive urination, thirst, or hot weather. 

However, when this change in water intake is coupled with other concerning signs like rapid weight loss, loss of appetite, or poor appetite, I recommend you consult your vet.

These could hint at underlying medical conditions such as diabetes mellitus, kidney disease, or cancer in dogs.

When Should I Be Concerned About My Dog Losing Weight?

Should I be worried if my dog is drinking more water than usual

If your dog is steadily shedding pounds without a clear reason, like increased physical activity or a change in diet, it’s time to turn to a veterinarian.

Unexplained weight loss in dogs should raise concern.

In fact, rapid or sudden weight loss can be associated with severe health issues, such as heart disease, liver disease, or cancer in dogs.

Regular check-ups, which include blood sugar tests, complete blood counts, and physical examinations, can help identify the cause.

Also, promptly addressing issues like dental or gum disease can prevent unexpected weight loss.


What to do when my dog is losing weight and drinking lots of water? Well, it could indicate various health issues.

Whatever the case, dog parents should always consult their veterinarian for the best guidance.

Regular health check-ups for your dog can also help prevent these issues. I hope your pet gets well soon! Good luck!


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Hi I am Mitchell. Dog Growth is a blog about dog caring and training where I share my experiences to my community. Hope you enjoy it!

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