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It can be a struggle when you see your once well-conditioned older dog begin to lose weight. Learn some common causes below!

Seeing your old dog starting to lose weight unintentionally is tough. Especially if your dog spent most of its life in good condition! For some senior dogs, you may see the weight loss occur slowly over time. Yet for others, it may be something that happens quickly and before you even have time to intervene!

Many dog owners are concerned about weight loss in their older dogs. This blog will focus on discussing some common causes of weight loss and what you should do if you see this in your older dog. We will also look at how you can make sure that your dog is still healthy.

Why Is My Dog Losing Weight Even Though He Is Eating?

Dogs can lose weight for all sorts of reasons. Here, we discuss several common causes of weight loss in older dogs that are still eating.

Diabetes Mellitus

Diabetic pets lose weight quickly because their bodies are not able to generate sufficient insulin to help them convert their food into usable energy. Most diabetic dogs will also have other signs in addition to weight loss with the most common one being increased drinking and urination.

Many owners with diabetic dogs will notice that their dogs are ‘always at the water bowl’ or recall that they were having to fill up the water bowl way more than normal. In dogs, diabetics are typically Type 1 which means their pancreas is unable to produce adequate insulin to regulate glucose adequately. Dogs that are diagnosed with diabetes will typically need insulin supplementation for life and can get very sick without it.

Signs of diabetes in dogs may include the following symptoms, excessive urination, increased hunger, and frequent water consumption. Cataracts may be developed because of diabetes.

Kidney Disease in Old Dogs

As dogs age, the cellular function of many of their organs and systems can begin to experience decline. Dog’s kidneys are a common place where we start to see disease. Many dogs will develop something called chronic kidney disease which is best picked up with bloodwork and urinalysis. Chronic kidney disease can gradually cause something called cachexia which is muscle wasting.

In addition, many dogs with chronic kidney disease will start having a decreased appetite because they do not feel as good. If you notice any signs of increased drinking, urination, decreased appetite or lethargy then that is a reason to bring in your pet to the vet right away.

It is important to note that not all dogs with kidney disease will look ‘sick’ or even show weight loss at various stages of the disease. Early in the disease, dogs will often look normal and even have good body condition. Something as subtle as a mild increase in thirst or urination may be the only sign you see. So even if you notice a small change in your dog, it’s best to have him checked out by your vet.

Because old dogs do not always show signs of kidney disease, it is even more essential that you keep a close eye on the overall health with regular visits to the vet even when they seem healthy. Performing bloodwork and a urinalysis performed on them annually or semi-annually is also recommended.

Cancer in Old Dogs

A common sign of cancer in old dogs can be weight loss and loss of muscle mass. This type of weight loss is often one of the first symptoms that many dog owners observe in their sick pets. Not all dogs with cancer will have weight loss so keep an eye out for changes such as decreased appetite, lethargy, new bumps, diarrhea or vomiting, increased drinking and urination, and limping.

The truth is that older dogs have very few ways to ‘tell you’ that something hurts or is off. So, changes such as lethargy and withdrawn behavior should prompt you to schedule an examination for your dog with your vet. The veterinarian can perform diagnostic tests to confirm or rule out the presence of cancer; once the diagnosis has been made, treatments will be available for your pet.

Heart Disease

Heart problems in dogs can easily go undetected for a long time because sometimes there are few, even subtle signs. Some will develop heart disease with age. Older dogs with more advanced lung or heart disease can certainly experience weight loss due to a process called cachexia. Parasites such as heartworm disease can also cause heart disease and contribute to the risk of heart failure in an older dog.

If you know your dog has a heart murmur and you are noticing weight loss, schedule an appointment with your vet to bring it up. For older dogs with a heart murmur, any signs of increased breathing rate or effort, reluctance to sit down or appearing difficult to get comfortable are all considered emergencies and veterinary care should be sought out immediately. If you are not sure if that is what you are seeing then call your vet or an emergency vet. It is always better to be cautious in these situations.

Gastrointestinal Disease

Another cause of weight loss can be gastrointestinal disease which can affect the stomach, intestines, pancreas, or colon. If your dog has any signs of vomiting or diarrhea even if it is chronic and they seem ‘ok’ otherwise, this can be a sign of underlying gastrointestinal disease. This can include anything from inflammatory bowel disease parasites, cancer or more.

Your vet may recommend starting with diagnostics such as bloodwork, ultrasound and/or X-rays, a fecal.

Inadequate Calories

On occasion, inadequate calories can be a cause for weight loss. So paying attention to what your dog eats compared to what they used to eat is important. Keeping a food journal and calculating total daily calories is also really helpful.

If you have multiple dogs or feed them all out of one bowl, it is best to stop that practice and have a feeding system in place so you can see who is eating what and how much. It is really hard to determine if a dog is getting adequate calories or changes in calories if you have multiple dogs sharing out of a bowl that is down all day.

How to Help Old Dog Losing Weight but Eating?

The first step to helping an old dog that is losing weight but eating is to try to find the cause. This means seeing your vet and doing diagnostics. They may be able to identify diseases or illnesses that can be diagnosed during a regular check-up. Depending on the underlying cause, some may be able to be cured or managed while others may require a more serious conversation.

Do not delay seeking treatment for a dog because you are worried about a diagnosis. Understanding what is happening will help you make the best decision for your dog. Some diseases may require frequent visits and follow-ups with your vet.

In terms of general recommendations, pay attention to the amount of food your dog is eating and the calories as well. Trying to enhance their food with a small amount of boiled chicken or white rice, can be helpful if they have a decreased appetite.

For decreased appetite, you’ll want to make sure you have identified the cause so that you can better help the pet. Sometimes switching up foods, supportive medications, and appetite stimulants can help.

Try weighing them once every two weeks (all dogs should have a proper weight that is neither too heavy nor too light). If in doubt about what exactly is going on internally speaking with your vet about dietary changes would be a good idea before introducing new things into the diet.


The first step to figuring out why your old dog is losing weight is figuring out the reason why. Start with a trip to the vet to see if some diagnostics help uncover this. Dogs hide illnesses well and so even if they 'seem ok' on the outside, unintentional weight loss in an older dog is most often a sign of something occurring under the surface.


Grab your seat to our free masterclass, 5 Ways to Extend Your Dog's Life taught by Dr. Tarantino and celebrity vet, Dr. Lippman. Learn their blueprint and the 5 secrets they swear by to help your best friend!


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