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Why is my dog losing weight?

Rapid or sudden weight loss can be an indicator of a more serious condition—here are a few of the potential causes to be aware of.


Adult Golden Retriever lying down in a kitchen next to a bowl.

Your dog's weight will change over the course of their lifetime, depending on their age, breed, whether they are neutered and any health conditions they may have. But if you've noticed your dog has suddenly and unexpectedly begun to lose weight, this could be a sign of a serious disorder. 

Not all sudden weight loss is due to a chronic condition, so make sure that you speak to a veterinarian as soon as possible to help work out what the problem is and what treatment is available for your dog. 


Gastro-intestinal disorders in dogs 

Weight loss can be a sign your dog is suffering from one of many possible gastro-intestinal disorders, which can affect their stomach and intestines. Other signs to look out for are chronic diarrhea or constipation, vomiting, dehydration and lethargy. When your dog is suffering from a gastro-intestinal problem, they may lose their appetite and begin to lose weight as digesting food causes them discomfort. 


Chronic renal failure in dogs 

A serious and common problem that occurs in 2% to 5% of all dogs, chronic renal failure is a condition where your dog's kidneys stop working effectively and aren't able to perform excretory or metabolic functions. The average age of diagnosis is six and a half years old, so it's a condition that often affects older dogs. Alongside weight loss, you may notice your dog is lethargic, weak and suffers with vomiting or diarrhea. 


Megaesophagus in dogs 

Weight loss is a secondary sign of a condition called megaesophagus, which prevents your dog from fully digesting and absorbing its food. In dogs with this illness, their esophagus swells, becomes enlarged and begins to malfunction as it no longer transports food to the stomach effectively. 

Puppy dog lying down on an examination table being checked over by a vet.

Liver disease in dogs 

Along with vomiting, anorexia and generalized lethargy, sudden weight loss is an early sign of liver disease. 


Exocrine pancreatic insufficiency (EPI) in dogs 

EPI is a disorder whereby your dog is unable to digest food properly as their pancreas isn't producing enough or the right digestive enzymes to support their system. This means they aren't getting the nutrients or energy they need, and will start to suffer weight loss. This condition is also characterized by chronic diarrhea and a ravenous appetite, as your dog attempts to get the energy it knows it is lacking by eating more food. 


Diabetes in dogs 

Diabetes is, unfortunately, a common condition among dogs. When it's poorly controlled, dogs are likely to lose weight relatively quickly—often a dog is diagnosed with diabetes after the initial period of increasing weight loss. The majority of diabetic dogs are middle-aged or older and are likely to already be fairly lean with a reduced body mass; if your dog fits this description, it's important to keep an eye on their weight to make sure it's stable. 


What to do if you notice sudden weight loss in your dog 

Because sudden weight loss is a common sign for some complex, chronic conditions, such as renal failure or diabetes, it's crucial you book a consultation with a veterinarian if you notice your dog has rapidly lost weight. Your veterinarian will conduct a series of tests, work out what is the likely cause for the weight loss, and offer a tailored treatment schedule for your pet. You may be asked to change their diet to help rebalance their weight and, in the case of gastro-intestinal problems, soothe and manage their signs. 

If you have any concerns about your dog's weight, speak to your veterinarian immediately. They'll be able to advise you. 

Jack Russel Terrier adult standing in black and white on a white background

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If you have any concerns about your dog’s health, consult a vet for professional advice.


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