What Causes Weight Loss in Dogs


Weight loss in dogs is associated with a range of conditions, both normal and abnormal.

Before we probe the common causes of canine weight loss, though, what constitutes weight loss when you’re dealing with dogs?

I. How Much Weight Loss in Dogs is Considered Problematic?

When weight loss amounts to more than 10% of a dog’s normal body mass, something is amiss. This estimate assumes that the weight loss is not triggered by either dehydration or fluid loss.

While this means a healthy adult pitbull weighing 50 pounds would need to lose 5 pounds before that weight loss is deemed clinically significant, for a teacup breed or Chihuahua weighing just 3 or 4 pounds, fractional weight loss in poundage can be cause for concern.

Check your dog’s weight regularly as a starting point. Also, watch out for any of the following symptoms of canine weight loss.

II. Symptoms of Weight Loss in Dogs

Look out for any of the following markers that commonly indicate weight loss in dogs:

  • Lethargy
  • Peeing more than normal
  • Changes to appetite
  • Vomiting
  • Diarrhea
  • Breathing problems
  • Panting
  • Coughing

III. What Causes Weight Loss in Dogs


When you notice your pooch unexpectedly losing weight, this can have you scratching your head and trying to work out the root case.

The most obvious and perhaps the most common cause of weight loss in dogs is simple math: insufficient caloric intake relative to energy expended. Common causes include:

  • A low-quality diet
  • Insufficient food
  • Excessive physical activity
  • Prolonged exposure to cold
  • Eating disorders and swallowing disorders
  • Digestive issues
  • Malabsorption of nutrients
  • Loss of nutrients through vomiting or diarrhea

Beyond these obvious underlying causes, a battery of diseases and health conditions result in weight loss at some stage.

  • Stress
  • Dental disease
  • Cancers
  • Parasites
  • Kidney disease
  • Heart disease
  • Gastrointestinal disorders


Stress and anxiety can sometimes impact a dog’s appetite to the extent it results in weight loss.

While dogs are remarkably adaptable, they are also very perceptive. Even minor changes to their surroundings can trigger stress-induced weight loss.

Dental disease

Sometimes, oral pain brings about weight loss in dogs. If your pup is unable to chew hard kibble due to gum issues or an abscess, this can cause his weight to plummet.

In the case of senior dogs with advanced dental disease, this is a vicious cycle that causes them to feel unwell while also losing overall body condition. To make things worse, oral bacteria can spread throughout the whole body.


Many types of cancer cause unexplained canine weight loss in dogs. These include:

  • Lymphoma
  • Osteosarcoma
  • Hemangiosarcoma

Sometimes, the tumor itself causes the weight loss, and sometimes the general pain and discomfort impacts activity and appetite with weight loss following.


Regular worming treatments means parasite-related weight loss in dogs is now much less common that it used to be.

If your dog does pick up parasites, you’ll need to use a broad-spectrum de-wormer then a monthly preventative medication.

Kidney disease

Chronic forms of kidney disease can cause weight loss in dogs. This affects both muscle and body fat, leading to an emaciated furball.

Heart disease

In many cases of advanced heart disease, dogs lose weight. By this stage, though, Fido losing a few pounds is probably the least of your concerns.

Gastrointestinal Disorders

Sustained GI issues can lead to dogs losing weight over time.

If your dog vomits often or suffers from frequent diarrhea, this will decrease the amount of nutrients available for his system.

When dogs are unable to properly digest or absorb foods, this can also lead to underweight pooches.

IV . How to Manage Weight Loss in Dogs


There’s no boilerplate answer to addressing weight loss in dogs.

The first thing you should do is schedule an appointment with your vet. A precise diagnosis will allow your vet to establish whether the weight loss is food-related, environmental, or triggered by a more serious underlying health condition.

Sometimes, the solution might be as simple as switching to a dog food for weight gain.

If the weight loss stems from something more sinister, you’ll be able to formulate a strategy for treating the health condition. This should, in turn, remedy the weight loss issue.

The prognosis for dogs with weight loss can be anywhere from excellent to worrying, depending on the specifics of the diagnosis. All you can do is arrange for the requisite examination, and then allow your vet to come up with the most effective course of treatment.

V. When Should You Contact a Vet About Weight Loss in Your Dog?

If you feel your dog is losing weight, you should always and immediately consult your vet.

In many cases, weight loss is a symptom of a more serious and troublesome health condition or disease. The earlier you intervene, the stronger your chance of restoring Rover to perfect health.

Once you suspect weight loss, you should check your dog’s weight several times a week. Record this so you can determine more accurately what’s going on.

VI. Conclusion

We hope today’s examination of what causes weight loss in dogs has given you some useful insights.

The most valuable takeaway from today is to take your dog to the vet as soon as you notice any downward fluctuation in his weight. In the best scenario, the vet can pinpoint a food-related issue that’s easy to fix. A less savory outcome is discovering your furball has a disease. The sooner you catch this, though, the more likely you are to prevent any adverse outcomes. Don’t feel like you’re overreacting or wasting your vet’s time. Rather, you’re doing the right thing as a responsible dog owner.

Don’t forget to bookmark BarkVA before you head off today. We bring you fresh content several times weekly focusing on all aspects of pet ownership. Pop back soon for more informative guides and product breakdowns!

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Jesse Hopping, CCDT

Jesse is a natural-born dog-lover certified dog trainer (CCDT), dog foster, and former volunteer at Richmond SPCA and surrounding dog shelters for over 10 years. Her pack includes a Bernedoodle and 3 Boston Terriers. She’s sipping caramel coffee and watching her pack play in the sun when she’s not writing blogs. Jesse has her Certified Dog Trainer designation from CATCH Canine Trainers Academy since 2018 and and majored in English from the University of Virginia.

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