My Dog Is Losing Weight But Seems Healthy

Is your dog losing weight but eating a normal (or increased) amount? If you aren’t trying to get him or her to shed some pounds, this could be a sign of a medical condition. To help prepare you for your dog’s visit to the vet, integrative veterinarian Dr. Julie Buzby discusses the 10 most common causes of weight loss in dogs.

If you’re not actively helping your pup lose some excess pounds, unexplained weight loss can be a bit concerning. And it can be downright alarming if your dog is eating the same amount of food, or worse yet,

If your adult or senior dog is losing weight but still eating, it is generally best to get your vet involved sooner rather than later. However, you can play an important role in the diagnostic process too. After all, you know your dog better than anyone else. It is amazing how many times something that a dog parent mentions during the examination helps point me toward the right diagnosis.

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With this in mind, my goals for writing this article are two-fold. First, I want to teach you how to gather the information at home that can help your vet help your dog. Then I want to equip you with knowledge about the top 10 reasons a dog might be eating but losing weight so that, again, you can partner with your vet to help your dog.

When it comes to solving any doggie medical mystery, a good physical examination and history come first. This often starts with a preliminary “check-up” in your own home. (But don’t worry— your vet will perform a comprehensive physical examination as well.)

To evaluate your dog at home, you may want to consider using my 5-minute tip-to-tail dog wellness scan method. While looking your pup over from head to toe, ask yourself the following questions:

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Then take this information (perhaps recorded on a piece of paper or in your phone) with you to the vet appointment. That way you can give your vet a clear and concise picture of what is going on with your dog.

Based on that information, your dog’s past medical history, and the physical exam findings, your veterinarian will discuss the next steps with you. This often involves diagnostic testing such as:

These tests can often help the vet further differentiate between the various causes of weight loss that we are about to discuss. (Or sometimes they may point to a condition that didn’t happen to make my top 10 list.)

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As mentioned, there are numerous diseases that cause weight loss in our canine companions. But there are 10 in particular that I want to highlight for you.

Kidney failure in dogs is one of the most common reasons for a senior dog losing weight but eating. Normally, the kidneys are responsible for filtering toxins out of the blood, then removing them from the body via the urine. Plus, the kidneys help maintain the delicate balance of electrolytes, fluid, proteins, and other substances in the body. However, when the kidneys become diseased, they can no longer perform these important functions. As a result, the dog becomes sick.

Dogs with kidney disease experience unexplained weight loss because they are breaking down fat and muscle, especially as they advance through the stages of kidney disease in dogs. Plus, these dogs typically experience other symptoms include vomiting, diarrhea, being a lethargic dog, and increased thirst and urination. Older dogs with kidney failure may also be more susceptible to urinary tract infections (UTIs in dogs). This can result in urinary accidents or seeing blood in the urine.

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Typically, the vet will use a combination of elevated kidney enzymes on bloodwork and changes in the urinalysis (e.g. decreased urine concentration), to make the diagnosis of kidney failure. From there, he or she may recommend some additional test such as urine cultures, X-rays, or ultrasounds to get a better picture of your dog’s situation. Based on that information, the vet will devise a treatment plan. It may involve fluid therapy (such as subcutaneous fluids for dogs), diet change, and/or certain medications to manage symptoms or slow disease progression.

Another common reason an older dog may be losing weight but eating is liver disease in dogs. Your dog’s liver has many important functions, from breaking down various nutrients to removing toxins from the body. It is no surprise then that when the liver is no longer working correctly, a dog can show a variety of clinical signs.

For example, dogs with liver disease may have trouble digesting, absorbing, or metabolizing nutrients properly. This can lead to weight loss. Additionally, they may experience abdominal pain, vomiting, jaundice (i.e. yellowing of the skin), fluid accumulation in the abdomen (i.e. ascites), increased thirst and urination, and dog nose bleeds (or other signs of abnormal blood clotting).

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Dogs with liver disease usually have elevated liver enzymes on bloodwork (e.g. high ALP in dogs). And they may also have changes to the liver size, shape, or architecture on imaging. The vet will use this information, any additional diagnostics that might be indicated, and an understanding of the underlying cause of the liver failure (if known) to create a treatment plan. Since there are a variety of causes of liver failure, the exact treatment may vary. But a special diet, or other supportive measures, tend to be part of the plan.

If you have ever had a toothache, you probably know how excruciating dental pain can be. However, dogs are stoic and the signs of oral pain in dogs can be subtle. This means it can go undetected for a period of time, sometimes until it starts causing weight loss.

In some cases of dental disease in dogs, it may appear that your pup still has a good appetite. But in other cases, he or she may start eating less. And dogs with severe oral pain may even choose not to eat at all. Thus, it is important to be vigilant for signs of oral pain like drooling excessively when eating, chewing on one side of the mouth, or dropping bits of dog food. Plus, you should watch for symptoms of general dental disease like bad breath, bloody saliva, or a dog losing teeth.

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If your vet suspects your dog’s teeth are to blame, he or she will probably recommend a thorough oral examination under general anesthesia. This allows your vet to evaluate and clean the surfaces of the teeth above and below the gum line. Plus, he or she can take dental X-rays to look for evidence of periodontal disease (i.e. inflammation of the structures surrounding the teeth), dog tooth abscesses, or other problems.

Sometimes the veterinarian may need to perform a dog tooth extraction if a tooth is broken, loose, or otherwise compromised. Or in other situations, your vet may refer you to a veterinary dentist for more specialized treatments like a root canal. The vet will also talk with you about at-home oral hygiene strategies like brushing your dog’s teeth. And he or she may recommend routine veterinary dental cleanings going forward.

No one ever wants to hear the word “cancer, ” but unfortunately it is another reason that an older dog may be losing weight. Sometimes cancer in dogs is a discrete tumor like a mast cell tumor in dogs or bladder cancer in dogs. Other times, it could be something more generalized like lymphoma in dogs or leukemia.

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Dogs with cancer can appear mostly asymptomatic at first. They may be eating normally but losing weight very slowly. Over time, they might start showing other signs depending on the tumor type. Some dogs develop a lump or enlarged lymph nodes in dogs. Others may have trouble urinating due to prostate cancer in dogs, or experience life-threatening internal bleeding from a ruptured hemangiosarcoma in dogs.

However, dogs with most types of cancer will also experience more generalized signs like vomiting, obvious weight loss, pain, coughing, and lethargy. These symptoms may be due to the original tumor or the spread of the tumor cells (i.e. metastasis) to other areas of the body.

Reaching a cancer diagnosis can look a bit different depending on the type of cancer. However, it often involves a fine needle aspirate or biopsy. These tests allow the vet to examine the tumor cells to determine if they are malignant (i.e. cancerous) or benign.

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Then, based on the type of cancer, your vet or a veterinary oncologist can discuss your dog’s treatment options. Thankfully, there are now numerous cancer treatments available for dogs, including surgery, radiation, chemotherapy, and immunotherapy.

On the other hand, some disorders can result in rapid weight loss in dogs, especially senior dogs. One such condition is diabetes mellitus (diabetes in dogs), which affects the ability of the body to use and store glucose (i.e. sugar). Normally, the pancreas releases insulin, which drives glucose from the blood into the cells. However, dogs with diabetes don’t produce enough insulin. Thus, glucose stays in the blood and cannot move into cells to provide energy.

Since the body can’t use glucose for energy, it ends up breaking down fat and muscle to use as alternative

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