Is your dog losing weight for no apparent reason such as a diet change or increased physical activity? Sometimes an animal can be encompassed by a condition that causes them to lose weight unintentionally. This is especially unhealthy for animals that are not overweight because it could cause them to become underweight which can be just as dangerous.

The first thing you should consider if you notice your dog is losing weight is dehydration.  Two-thirds of the body is made of water, so sudden weight loss may be caused by water loss, as opposed to fat or muscle loss. To combat dehydration watch for issues such as dog diarrhea and make sure there is fresh water available at all times. If your dog is refusing to drink water, a trip to the veterinarian is necessary as dehydration can be fatal if not treated.

There are several other conditions that could cause your pet to have unhealthy weight loss:

Toothaches and dental disease:

Dogs with toothaches or dental disease often lose weight because eating is painful; dental disease can also cause disease of other organs such as the kidneys, liver and heart which will essentially lead to weight loss.

Intestinal worms or heartworms:
Dogs with intestinal worms or heartworms are likely to lose weight because nutrients are being removed from their body by the worms; worms will also cause certain organs to work harder leading to unnecessary energy usage, and weight loss. If your dog is losing weight it would be a good idea to have your vet do a stool sample to see if worms are the culprit.

Vital organ diseases:

Diseases in vital organs, including the heart, lungs, kidneys, liver and spleen often cause pets to lose weight.  When these organs are compromised, they must work harder to function, leading to higher energy expenditure.  If you pet has a disease of any of their organs, you will notice that they are more tired than usual.

Cancer in any area of the body will cause your dog to lose weight. Several cancers wipe away nutrients, causing degeneration of fat and muscle.  Also, a substance called TNF is released in the body by the liver which causes the cells to use more energy than normal. Your dog will lose his appetite because of TNF and will not want to eat, another characteristic of most cancers. 


Just like in humans, dog depression can cause changes in appetite which could bring with it unhealthy weight loss or gain.

It’s a given that pets will begin to lose weight as they age.  They could begin to experience pain in the form of arthritis, weakening of organs, changes in appetite as food loses taste or confusion and depression. Age brings with it its own set of ups and down, make sure to visit the vet if you feel your dog’s aging is causing unhealthy weight loss.

The moral of the story… if you see your dog is losing weight unintentionally, it’s necessary to figure out the underlying cause.