Weight Loss in Dogs | Why Could My Dog Be Losing Weight

Brown dog sitting in a field

If your dog seems to have been losing a bit of weight (or more) for a while and you can’t understand why, it’s a good thing you’re reading this article. We made a list of some of the most probable causes of weight loss in dogs and we even came up with a couple of solutions.

Could the Weight Loss Be Healthy?

Let’s begin by making the difference between what could possibly be healthy weight loss and a probable manifestation of a medical condition. If your dog has been engaging in a lot more exercise, you’ve been feeding him weight loss food, or any changes regarding his or her living environment have happened recently, the phenomenon could be natural.

Some other causes of somewhat healthy weight loss can be a change in diet or a change in schedule, as well as more access to the outdoors. For example, if you used to live in an apartment and you moved into a house with a yard and you leave your dogs out during the day, they will naturally engage in more physical exercise than they did when they were cooped up in a small living space.

Another aspect worth noting is that many geriatric pets lose weight as part of the normal aging process. However, this doesn’t happen rapidly, but rather with time.

Rapid, Dramatic, or Persistent Weight Loss

If you notice any of these, it’s safe to say that you have to take Fido to the vet as soon as possible. Dramatic weight loss is what happens when your canine companion loses more than 10% of his whole body weight. This, along with sudden weight loss in dogs, can be an indication that there might be more to what you are seeing.

Top Causes of Weight Loss in Dogs


Internal parasites basically consume the nutrients that your dog should get from the food that he or she eats. Many dogs with parasites (particularly those that have tapeworm infestations) can exhibit sudden weight loss, and that should give you a pointer that something’s wrong.

Whenever you are confronted with this issue, it is a good idea to start analyzing your dog’s behavior and the way he/she ‘goes to the bathroom.’ If you notice any change in the stool, especially in terms of consistency or if you see any larvae or pieces of parasites in your dog’s feces, it’s safe to say that you should deworm your canine buddy. Keep in mind that medication for the purpose can be dangerous if you do not know what the right dosage is. You never want to overdo it with these meds – your dog is already being attacked by the parasites; he doesn’t need any abuse from a chemical substance, too.

Liver disease

There are many signs that could indicate liver disease, and weight loss is just one of them. It’s often associated with several others such as loss of appetite, a yellowish tint to your dog’s eyes, tongue, or gums, a change in the color of your dog’s feces or urine, and also diarrhea or vomiting.

Dogs that suffer from liver pathologies don’t get the necessary nutrients from their food. The liver plays an essential part in the digestion process, being in charge of synthesizing lipids, but also a variety of other substances, including proteins and carbs. It’s also the place where bile is secreted (the gallbladder), and bile is essential for digestion.

The point is that, if the liver is sick, the dog’s body has to get the necessary nutrients from other sources – such as fat that it has stored in fatty tissue and muscle tissue. That’s why the weight loss happens.

Dental problems and/or mouth lesions

This one is rather self-explanatory. Periodontitis, gum disease, infections, and anything else that’s wrong with the oral cavity of a dog can prevent the animal from feeding. You’ll notice that your canine buddy often has to adopt all sorts of body positions as he tries to chew his food so as to avoid touching the area in the mouth that could be painful.

Some dogs refuse food altogether, no matter how much they actually love it. The pain can be so severe that aggravating it might just not be worth it for them. If your dog stops feeding or has any problem chewing, take him or her to the vet. If you can’t right now, try feeding some soup or wet food to Fido and see what happens. If he consumes soup but refuses anything that’s harder, it’s highly likely that he has an oral issue.

Thyroid problems

Hormonal imbalances are a little more complicated to detect and even diagnose. Pretty much the only way that they can be discovered is through blood tests and sometimes, as is the case with the thyroid gland, for example, ultrasonography can be used, as well.

Hyperthyroidism triggers rapid weight loss because it creates a rapid metabolism. No matter how much your dog might eat, his or her body’s metabolism will either break down the nutrients in the food too quickly, or it won’t be capable of processing them at all — in which case they will be passed through the system without even being absorbed. If your dog hasn’t lost his appetite or actually has an increased appetite but is still losing weight, a checkup is necessary.


In dogs, diabetes has the same clinical manifestation as it does in humans. As is the case with thyroid hormone imbalances, in this situation you’ll notice that your dog does consume food, but he still loses weight. The problem is also hormonal, but it’s caused by a pancreas deficiency to produce enough insulin.

If the quantity of insulin is not enough, your dog’s body is incapable of absorbing the sugar in his blood. In other words, the nutrients are processed and do reach the blood as they should, but they never get to feed the organs they have to.


Some types of cancer can cause weight loss, but there are a variety of neoplasms that can affect your canine buddy, so there’s no way of you knowing what he or she is suffering from. However, some of the most common kinds of cancer that can produce weight loss consist of abdominal tumors. Whether they are located in the liver, the intestine, or the stomach, weight loss can be a symptom of all.

What Can You Do?

As you can see, there are too many causes of weight loss and it’s almost impossible for a pet parent to know just what the right one is. That is why we recommend thinking back and analyzing both your pet’s behavior, as well as some of the things that have happened recently. Has anything changed in your living environment, Fido’s feeding or exercise schedule, or his diet? Have you both lost a canine companion? Grief can also cause weight loss in dogs.

It is also highly recommended that you keep an eye on your dog in terms of his appetite, activity level, and any other changes. Is he or she experiencing lethargy, vomiting, poor appetite, diarrhea, or any other symptoms? Ask yourself these questions and jot them down on a piece of paper so that you don’t forget any and describe them to the vet when you go to the clinic.

At the Vet

If nothing seems to work and you want to get to the bottom of this and help your dog regain his or her health (and weight), you have to go to the vet clinic. There, the veterinarian will ask you several questions to find out more about your pet’s history. A physical examination will be performed, as well as some basic lab work.

It’s highly likely that the blood work is going to show an indication of what could be wrong, and it is often associated later on with either an X-ray or an ultrasound.

If there is any suspicion that your dog could be suffering from an obstruction or gastrointestinal cancer, a barium study might be necessary, as well. What this means is that your dog is going to receive a contrast substance orally and a series of X-rays will be performed so as to evaluate the progression of said substance through the esophagus, stomach, and intestines.

What If Nothing’s Wrong?

If your dog starts to lose weight for no apparent reason and the vet says that Fido doesn’t suffer from any medical condition, there are a couple of things that you could do to make him pack some pounds. One of them is switching to a diet that provides more calories. There are specially formulated foods that have more calories than regular ones, and they are often intended for senior dogs.

You could also try to limit the amount of exercise that your dog gets, but if your dog has access to the outdoors all day long, that could prove to be difficult. Probiotic supplements, as well as taste enhancers (such as oils or cheese added to the regular food), can also convince your dog to eat more. Just make sure you don’t overdo it because oils in excess can trigger digestive issues (such as diarrhea).

Finally, nothing’s better than being there for your dog, especially if he or she is going through a rough time emotionally. Try to spend as much time in the company of your canine buddy as you can, and if everything fails, don’t hesitate to consult an animal behavior therapist, especially if you suspect that he or she is suffering from depression.



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