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Weight Loss in Dogs: Signs of Possible Illness

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If you notice your dog is losing weight for no reason, it's important to see a veterinarian as soon as possible. Weight loss in dogs is a common symptom of chronic illness.

Weight Loss in Dogs: Signs of Possible Illness

Written and verified by the biologist Paloma de los Milagros

Last update: 22 December, 2022

Weight loss in dogs is normal as long as there’s a good reason, such as plenty of exercise or a new diet program. However, when drastic weight loss seems to happen for no reason, then it may be the sign of a more serious issue.

In general, weight loss in dogs is clinically significant when it exceeds 10% of a dog’s normal body weight. In order to make this calculation, there are tables that serve as guides, according to a dog’s breed and age. However, it’s important to point out the possibility of small variations in an animal’s ideal weight because of genetic factors.

At the same time, it’s important to keep in mind that other common factors may also cause minor fluctuations. For example, seasonality or stress can affect an animal’s physical condition. However, these variations tend to be temporary in nature and don’t necessarily pose a risk.

How to evaluate weight loss in dogs

In cases of severe weight loss in dogs, it’s important to consult with a veterinarian. However, owners can conduct a check themselves in the following way:

Passing their hands along the dog’s body, to see if they can feel the dogs ribs due to a lack of fat below the skin.
Observing the dog from above or from the side, to see if they can observe a defined waistline.
After weighing their dog, owners confirm a notable drop in weight in comparison to previous weights.

There are some routine questions that animal health professionals tend to ask. These have to do with appetite, possible swallowing difficulties, and the appearance of their feces. Sterilization and the frequency with which preventative heartworm treatment is administered are also important factors to consider.

In general, your vet will also perform a complete physical examination on your dog as well. This usually involves blood tests, urine and stool tests, and even X-rays.

Possible illnesses involving weight loss in dogs

Weight loss in dogs can be associated with a number of chronic illnesses. The most common illnesses involving weight loss are:

Gastrointestinal disorders. In these cases, weight loss goes hand in hand with vomiting, constipation, and lethargy. These symptoms cause a lack of appetite and, in turn, decreased body mass.
Chronic renal insufficiency. In this case, animals become weak because the excretive or metabolic function of the kidneys is insufficient.
Megaesophagus or esophageal dilatation. Dogs with this condition–normally large dogs–have a swollen and enlarged esophagus. As a result, the organ is unable to transport food effectively.
Exocrine pancreatic insufficiency (EPI). This is when the pancreas fails to produce necessary digestive enzymes, whether in regards to quantity or quality. This means that the dogs won’t obtain the necessary nutrients. Despite the resulting thinness, the dogs also have a voracious appetite. The same occurs with hepatic disorders.
Diabetes. This pathology is quite common among dogs, especially older dogs. Excessive thinness can be a symptom of this condition. In fact, it’s one of the symptoms that helps veterinarians come to a diagnosis.

The list of chronic illnesses linked to weight loss in dogs is quite long. This is because most illnesses have an impact on a dog’s appetite and activity level. In the case of unexplained weight loss, it’s best to play it safe and see a specialist as soon as possible.