Why is my dog losing weight?

When your dog suddenly loses a significant amount of weight, this is a cause for alarm for many dog owners. While for some obese pets this may seem to be a desirable outcome, it’s still reason to get concerned. If your is losing weight without any efforts on your part – like a change of diet – this can be a sign of a serious health condition.

There are a few question you may want to ask yourself, when you are concerned about your pet’s weight loss.

  • Has your pet’s appetite changed?
  • Has your pet been ill, vomiting, diarrhea or showing other symptoms of an illness?
  • Has there been a change to your dog’s home schedule?
  • Has your dog increased their activity level, or has there been a change in their diet?

If you can’t find a clear cause and your dog is losing weight rapidly, then it is recommended you take them to a veterinarian as soon as possible.

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Medical reasons of why your dog could be losing weight

There are a few non-medical threats that could be the cause of your pet losing weight, although these often will not result in dramatic weightloss rapidly. A change in diet, activity level, a change in schedule or a new move can all contribute to your pet losing weight. These items are often not a serious concern; maybe your dog just needs to get adjusted to the changes. Old age also can contribute to some weight loss but, while a little weight loss is normal rapid weight loss should also be a concern for older dogs. It might be better to put them down, than to let them suffer – even though both decisions will be difficult.

However, if your pet has lost a significant amount of weight – more than 10% of their normal body weight – than this is a cause for concern. Rapid weight loss in dogs could be a warning signal of a more serious underlying health issue, Some of these issues include:

  • Liver disease
  • Periodontal disease
  • Kidney failure
  • Cancer
  • Diabetes
  • Chronic gastrointestinal obstruction
  • Neuromuscular disease
  • Orthopedic disease


If you have noticed your dog has rapidly lost weight, you will want to take them to a veterinarian, so they can perform tests to find out what the underlying condition is. The veterinarian will ask you when you first noticed the weight loss in your dog, as well as questions about their appetite and behavior. The veterinarian will also do a physical examine. Often they can narrow down what could be causing the weight loss, by establishing where your pet may have discomforts or abnormalities. Blood-work is also often done to rule out Lyme disease. A complete blood count is conducted along with a urine and fecal analysis. X-rays and ultrasounds are also often done to give the veterinarian a better look at what is going on inside your dog’s intestines. This can help detect obstruction in the digestive track, or stomach, as well as any unusual masses that could be cancerous.

Sometimes weight loss in your dog is not much of a concern and then it can be explained by your dog’s change of diet or routine. However, if the weight loss is more than 10% – and without an obvious explanation – this should be a warning signal to take your dog to a professional vet, in order to be diagnosed.

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