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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 symptom of a serious disorder.

Not all sudden weight loss is due to a chronic condition, so make sure to speak to a vet 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 symptoms to look out for are chronic diarrhoea 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 which 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 which often affects older dogs. Alongside weight loss, you may notice your dog is lethargic, weak and suffers with vomiting or diarrhoea.

Megaesophagus in dogs

Weight loss is a secondary symptom 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, refusal to eat and generalised 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 characterised by chronic diarrhoea 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 if you notice sudden weight loss in your dog

Because sudden weight loss is a common symptom for some complex, chronic conditions such as renal failure or diabetes, it's crucial you book a consultation with a vet if you notice your dog has rapidly lost weight. Your vet 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 symptoms.

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

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

Find a vet

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

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