10 Reasons Why Your Dog Is Losing Weight But Eating

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While it’s not uncommon for dogs to lose a few pounds once in a while, any sudden and unexplained weight loss is a huge red flag for all dog owners. If your dog is losing weight but eating, a visit to your veterinarian is in order. 

Like people, dogs can lose weight for many reasons. Rapid weight loss can be a sign of serious underlying health conditions. But it may also be that your dog is more active and burning more calories than before. 

Weight loss that exceeds more than 10% of your dog’s normal body weight is a cause for serious concern and warrants a trip to your veterinarian.

Anything less than 10% isn’t considered clinically significant, but you should keep a close eye on your pooch and monitor their weight.

DISCLAIMER: We are not veterinarians. If you’re dog is suffering from any health issues please contact your veterinarian.

Yellow Labrador Retriever eating his bowl of food.

If your dog continues to lose weight for no apparent reason, schedule an appointment with your vet. 

It’s extremely stressful to watch as your dog’s weight melts off before your eyes for no apparent reason!

Obesity is a big problem for many dogs, but being emaciated is just as serious and shouldn’t be overlooked.

Keep on reading to find out the most common causes for sudden weight loss in dogs and what you can do about it. 

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Why Is My Dog Losing Weight But Still Eating?

It’s completely normal for your dog’s weight to change over the course of its lifetime. Factors such as diet, age, breed, and health problems can affect your dog’s weight and cause weight loss. However, if you have detected that your dog is eating well but still losing weight, then speak with your veterinarian as soon as possible. 

While dogs can lose weight for many different reasons, getting slimmer is never normal unless your dog is on a planned diet. If your pooch lost a lot of weight suddenly, despite having a healthy appetite, don’t panic! Instead, take your dog to the veterinarian so they can identify the problem and offer your pup the necessary treatment. 

Listed below, are the most common causes why your dog is losing weight but eating:

1. Dietary Changes

Not all cases of weight loss in dogs are caused by diseases. You may be surprised to learn that changing your dog’s food is one of the most common causes of weight loss. 

You may think, this can’t be the case since I haven’t changed my dog’s food in years. However, while your dog may be eating the same brand of kibble, it doesn’t mean that the manufacturer didn’t change the formula in the meantime. 

Not suspecting a thing, you continue feeding your pup the same amount of dog food as before, but alas the new formula has 10% fewer calories. At the end of the day, your dog ends up eating fewer calories than it needs and, as a result, starts losing weight sooner or later. 

These changes are easy to miss since many dog foods are labeled in a very confusing way. So, before you jump to the conclusion that your pup is sick, check the food’s ingredient label and see how many calories it has per serving. 

If the food is the same as before, schedule an appointment with your veterinarian. But, if it turns out that the formula was changed and has fewer calories, simply start feeding your dog more of it. 

2. Intestinal Parasites

While weight loss due to intestinal parasites is not as common as it once was, it is still a viable possibility. 

While most dog owners stay up-to-date with monthly deworming treatments, which offer protection against intestinal parasites and heartworms, , there are many different types of intestinal parasites, and not all deworming treatments are equally effective. For example, many treatments can’t kill whipworms, but your dog can get infected by ingesting the eggs from contaminated water or soil. 

The main issue with intestinal parasites is that they consume all the food the dog eats, thus depriving it of all necessary nutrients. Intestinal parasites may be to blame if your dog is eating a lot but losing weight. 

Besides weight loss, intestinal parasites can cause the following symptoms:

  • Diarrhea
  • Vomiting
  • Increased gas
  • Abdominal swelling
  • Dehydration

Luckily, intestinal parasites are easy to diagnose through a fecal exam and are treated by a broad-spectrum dewormer. After a successful treatment, a monthly deworming medicine is the best preventative. 

3. Diabetes

Unfortunately, diabetes is often diagnosed in older dogs, especially in females. Dogs with diabetes start losing weight rapidly since their bodies can’t get the energy from the glucose and instead try to convert fat or protein into energy.

If your older dog is losing weight but eating and is also drinking a lot of water, you should take them to your veterinarian. Most dogs with diabetes lose weight very quickly and may also start to lose muscle mass. 

And since diabetes causes excessive thirst, your dog will also have to urinate excessively and may have accidents in the house even if properly housetrained

The most common symptoms of diabetes in dogs are:

  • Weight loss
  • Excessive thirst
  • Excessive urination
  • Increased appetite
  • Cloudy eyes
  • Chronic or recurrent urinary infections

If your dog is experiencing any of these symptoms, it’s important to take them to the vet right away. Your veterinarian will run blood glucose tests and a urinalysis to determine whether your dog has diabetes. When the diagnosis of diabetes is confirmed, the treatment will include insulin shots and a specialized diet. 

4. Maldigestion 

Maldigestion disorders, such as exocrine pancreatic insufficiency, hamper the body’s ability to break down food into usable nutrients. This means that all essential nutrients your dog eats every day just pass through their digestive system without being absorbed by the body. 

A dog with a maldigestion disorder will have a healthy appetite but will continue to lose weight. Besides the notable weight loss, your pooch may also have diarrhea, loose yellow stool, and gas. However, these symptoms alone aren’t enough to diagnose the problem.

Therefore, you will need to take your dog to the veterinarian who will perform a full physical exam and run tests. Your veterinarian will most likely take a stool sample and test your dog’s blood for digestive enzymes. 

5. Malabsorption

Malabsorption disorders interfere with the body’s ability to absorb nutrients from the intestinal tract. Inflammatory bowel disease is one of the most common malabsorption disorders diagnosed in dogs. 

If your dog is eating a lot but losing weight and also vomits, has diarrhea, or foul-smelling loose stool, they may have inflammatory bowel syndrome. The exact cause of this disease isn’t completely understood, but it leads to inflammation of the intestines. 

The initial testing for inflammatory bowel disease includes fecal examination, blood testing, and an X-ray or ultrasound of the intestines. There is no cure for this disease, and treatment consists of a specialized diet, probiotics, and anti-inflammatory drugs. While inflammatory bowel disease is a chronic condition, your dog can lead a normal life with a change of diet and appropriate treatment. 

6. Dental Disease

Dental disease is a common problem for many dogs, especially seniors. Broken or infected teeth, gingivitis, or gum disease can be extremely painful and make it hard for your dog to properly eat food. 

Since dental problems make chewing very painful, many dogs stop eating their food and start losing weight. However, dogs who aren’t experiencing severe oral pain may continue eating but still lose weight because they are unable to chew properly. 

The most common symptoms of dental disease are:

  • Bad breath
  • Difficulty eating and chewing
  • Excessive drooling
  • Swollen or bleeding gums

If your dog is losing weight and has any of these symptoms, take them to the veterinarian for a dental exam. Bear in mind, if dental disease isn’t diagnosed and treated in time, oral bacteria can spread throughout your dog’s body and affect the heart, liver, or kidneys. 

When spotted in time, dental disease is fairly easy to treat and most dogs start eating normally once the issue is resolved. Since dental problems can have big repercussions for your dog’s overall health, you should be proactive and start brushing your dog’s teeth from a young age. 

7. Kidney Disease

As your dog gets older, its organs can’t work as effectively as before. While weight loss can be a symptom of many conditions, dogs with kidney disease don’t start losing weight immediately. Instead, weight loss is typically associated with advanced forms of kidney disease. 

Dogs can experience acute and chronic kidney failure. With the latter, the disease progresses slowly over the years and is usually diagnosed in older dogs. Chronic kidney disease is caused by an underlying illness, hereditary conditions, and dental disease. 

The most common signs of kidney problems in dogs include:

  • Increased thirst
  • Excessive urination
  • Weight loss
  • Pale gums
  • Diarrhea or constipation
  • Vomiting
  • Depression

Since kidney failure is a life-threatening condition, it is essential that you take your dog to the veterinarian if you notice any of these symptoms. The treatment for kidney failure depends on the severity of your dog’s symptoms and whether the condition is acute or chronic. 

8. Liver Disease

Liver disease is a common condition in dogs and another potential cause of your dog’s weight loss. Since liver disease has similar symptoms to those of other health problems, many owners don’t realize that something is wrong until it’s too late. 

In most cases, liver disease is the result of aging, but it can also be genetic or caused by an infection, fatty food, or certain plants and medications. Besides weight loss, dogs with liver problems can also exhibit the following symptoms:

  • Vomiting 
  • Diarrhea
  • Increased thirst
  • An unstable walk
  • Confusion
  • Jaundice – yellowish eyes, tongue, or gums

While liver disease is often seen in older dogs, young dogs can have it, too. If your dog is losing weight and experiencing any of these symptoms, take them to the veterinarian as soon as possible. Your dog’s treatment will depend on the severity of liver damage and the problem that caused it.

9. Heart Disease

Like with kidney disease, dogs with heart problems don’t start losing weight right away. In fact, early symptoms of heart disease in older dogs are so subtle that most owners ascribe them to the normal age-related slowing down

Since heart disease can lead to congestive heart failure, it’s important that you know the symptoms so you can get your dog the help they need. 

Dogs with early-stage heart disease may experience the following symptoms:

  • Coughing
  • Tiring easily
  • Exercise intolerance
  • Excessive panting
  • Restlessness

As heart disease progresses, your dog may develop more symptoms including:

  • Swollen belly due to fluid build-up
  • Fainting
  • Change in tongue and gum color
  • Weight loss

Heart disease is a serious condition, so it’s crucial that you take your dog to the veterinarian as soon as you notice any of these symptoms. When diagnosed in the early stages, heart disease can be treated, and with proper care and regular checkups, your dog can live long and have a normal, happy life. 

10. Cancer

Cancer is another potential disease that can cause your dog to lose weight despite eating the same as before. There are many different types of cancer in dogs, and unfortunately some types don’t cause any symptoms until they have spread. 

Cancer is generally more common in older dogs, but that doesn’t mean that adult and younger dogs can’t get it. Like in people, malignant forms of cancer can be fatal, even when diagnosed early on and treated aggressively. 

In dogs, weight loss is associated with several forms of malignant cancers including osteosarcoma, hemangiosarcoma, and lymphoma.  With these types of cancer, a dog may start losing weight due to the tumor’s metabolic demands or because the dog is in so much pain that it can’t eat. 

While extremely difficult, try not to panic and automatically assume that your dog’s weight loss is due to cancer! There are many diseases that can cause weight loss in dogs, so take your pooch to a veterinarian for a full checkup. And if your dog’s weight loss is due to cancer, consult your vet about all available treatment options and do what’s best for your dog in the long run. 

FAQs About Why Is My Dog Losing Weight But Still Eating

Why Is My Dog Getting So Skinny?

Weight loss in dogs is the result of a calorie deficit. This may be caused by high energy demands, poor quality food, or a number of health issues. A sudden weight loss can be caused by many different diseases including dental problems, intestinal parasites, diabetes, and cancer.  

What Should I Feed A Dog That Is Losing Weight? 

If you have an underweight dog, you should take them to a veterinarian to rule out any potential health problems first. If your dog has a health problem, your vet will advise you on the course of treatment and also tell you what to feed your dog to help them gain back the lost weight.

Generally, if you want to fatten up your dog start feeding them food that contains more calories. Find the highest quality food that you can afford, and make sure that it’s made from healthy and wholesome ingredients. Additionally, you can help your dog to gain weight by feeding four smaller meals throughout the day.

How Many Times A Day Should You Feed A Dog? 

Adult dogs generally should eat twice a day – once in the morning and once in the evening. However, puppies under five months of age should be fed three or four smaller meals a day or as instructed by your veterinarian. Keep in mind, all dogs are individuals and how often your dog should eat will depend on their age, size, breed, and activity level.  

Why Is My Dog Losing Weight And Drinking Lots Of Water?

Weight loss and excessive thirst can be symptoms of many different health problems. Dogs with kidney failure, diabetes, or Cushing’s disease may experience these symptoms, so don’t hesitate to take your dog to the veterinarian as soon as possible. These conditions are usually seen in older dogs, but adult and younger dogs can also develop acute kidney failure. 

Furthermore, increased water consumption can be a sign of dehydration, so make sure that your dog has access to fresh and clean water at all times. 


An unplanned and sudden weight loss in dogs is never normal and can be a sign of a more serious health problem. If your dog is losing weight but eating, it’s very important to figure out what is causing the rapid weight loss. The most common causes of weight loss in dogs are:

  • Change in diet
  • Underlying health problem
  • Poor quality food

Since sudden weight loss in dogs is always alarming, so don’t hesitate to call your veterinarian and schedule an appointment as soon as possible. 

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My Dog Eats But Also Loses Weight!? - 10 Reasons Why & What You Can Do - Yellow Labrador Retriever lying on ground with his bowl of food.
My Dog Eats But Also Loses Weight!?

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10 Reasons Why Your Dog Is Losing Weight But Eating was last modified: March 21st, 2021 by LTHQ

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