Weight Loss In Older Dogs: 12 Causes and Solutions

Last Updated: April 18, 2023

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As your canine companion starts to get a bit long in the tooth, you might notice some changes to their behavior, activity levels, and physique. It's perfectly normal for canine bodies to go through some changes as they get older.

Most tend to gain a few pounds as their energy levels start waning and they begin to spend more time lying around. In fact, most veterinarians recommend diet changes to prevent this from happening.

While weight gain is to be expected, what happens when the opposite occurs?

skinny older senior dog that lost weight

There are several reasons why your dog could be dropping weight. Generally speaking, if your dog loses 10 percent of their body weight within a few months, it's considered to be rapid weight loss.

Of course, there's no one-size-fits-all answer to the issue. All dogs are different, so weight loss doesn't necessarily mean that there's a cause for panic. The key is to be able to understand the symptoms and know when to take action.

Here are some of the most common reasons why older dogs lose weight and what you can do to help.

12 Common Reasons why Older Dogs Lose Weight

1. Dental Problems

Think of the last time you had a toothache. You probably avoided eating just to keep the pain at bay. The same could be happening to your dog. Cracked teeth, periodontal disease, mouth sores, and abscesses could be the culprit.

Usually, you can identify dental issues by taking a quick glimpse at those chompers. Be careful though! Dogs can lash out when they're in pain.

If you smell a strong odor emanating from their mouth, you could be looking at tooth decay. Other signs might include excessive drooling and pawing at the mouth.

The easiest way to absolve this problem is to take your dog to the vet. A detailed cleaning could eliminate built-up bacteria. Your dog may also require extraction. While it's never fun to see your dog lose teeth, removing damaged teeth can provide the relief they need to start eating again.

Related: How to Soften Dry Dog Food for Seniors & Dogs with Bad Teeth

2. Malnutrition

This is an issue that's commonly seen among stray dogs or those who are not in a great home. Chances are, you won't have to deal with malnutrition problems at home. Essentially, malnutrition is when dogs aren't getting enough nutrients to support their bodies.

They may start to look emaciated. You might notice that their ribs are becoming visible and that they have difficulty moving around.

High-quality food is key to combating malnutrition. Luckily, most commercially available foods are designed to meet the dietary needs of canines.

Take your pup to the vet to ensure that there's nothing else going on. Your vet may provide some fluids through an IV tube to kickstart your dog's journey to better health.

3. Dehydration

Sometimes, it's not a lack of food that's the problem. If your dog is not consuming enough water, they could start to drop the pounds pretty swiftly. D

Dogs sometimes ignore their water bowl because they don't feel thirsty enough to take a sip. In some instances, there could be issues with the water quality that's turning your dog off.

Give the bowl a good cleansing and switch to filtered water. If that doesn't entice your dog to start drinking regularly, you can turn towards canned food or toppers.

Canned food has very high moisture content and is packed with flavor. That extra boost of hydration can do a lot to improve your dog's overall health.

4. Parasitic Infection

Can fleas cause weight loss? You might be surprised to find out that those pests can affect your dog's body in more ways than just causing some itchiness.

You see, fleas can lead to a parasitic infection. All it takes is for your dog to swallow an infected flea.

Parasitic Infection

Tapeworm is one of the most common parasites to affect dogs. The tapeworm will latch onto your dog's intestinal tract and leech essential nutrients from everything they eat.

As time goes on, the tapeworm will get larger until it starts to break off and appear in the feces. The same goes for ring and hookworms.

Because those parasites are using nutrients to grow, your dog's body has to pay the price. Sudden weight loss and insatiable hunger are very common symptoms.

The good news is that worms are relatively easy to treat. You can use an over-the-counter medication to kill the parasites in a couple of days. Alternatively, you can go to your vet for guidance. After the infection is taken care of, your dog's body should slowly get back to normal.

At this point, you should consider investing in a flea preventative to ensure that you don't have to deal with the problem in the future.

5. Diabetes

Diabetes is a life-changing condition. However, it can be managed with proper care. It's a common cause for older dogs losing weight because the body is not able to use glucose for energy.

Low insulin levels change the way that the body uses glucose, forcing it to look elsewhere for energy. Oftentimes, fat and proteins are used. Thus, the pounds start to melt off.

The problem with diabetes is that it can affect your dog's overall health. It causes extreme lethargy, increased urination, and a voracious appetite.

If you suspect that diabetes is to blame, you need to seek veterinary help as soon as possible. Ignoring the problem can lead to diabetic shock and possibly death. Your vet will work with you to manage the condition. Oftentimes, this involves insulin injections, a change in diet, and some modifications to your pup's lifestyle.

Related: Top 5 Best Dog Foods for Diabetic Dogs

6. Emotional Stress

While we would all love to think of our pups as happy-go-lucky companions, they can experience emotional stress just the same. Loss of appetite in older dogs can be caused by anxiety or depression. When your dog suffers from these mental conditions, they may go days without eating.

You'll be able to spot the signs pretty quickly. Emotional stress causes a noticeable change in behavior and overall demeanor. Instead of jumping up to greet you with kisses, they may spend most of the day sleeping or lying on the couch. 

You can work with a behavioral specialist to tackle this problem. Typically, treating emotional issues involves spending more time with your pup and changing up their routine a bit. 

Instead of leaving them to their own devices, you may want to consider investing in mental stimulation toys. Or, you can bring them to a doggy daycare center when you're away. Anything that will bring them more joy can help.

7. Liver Disease

Liver disease, as well as gallbladder disease, is another major health condition you should be wary of. With liver disease, your pup's liver isn't able to function properly. Thus, it can't metabolize and detoxify.

thin senior dog lying on the floor

This results in a significant decrease in essential nutrients your dog needs to stay healthy. Like with diabetes, your dog's body will turn to fat deposits for nutrients.

There are a lot of symptoms to look out for with liver and gallbladder disease. Not only will your dog have no appetite, but they might be in physical pain.

Panting, howls, and general irritability are telltale signs.

Other symptoms include lethargy, diarrhea, and vomiting. Physically, your dog may also exhibit some alarming symptoms. For example, their eyes or skin might start to turn yellow and their gums will become pale.

A trip to the vet is crucial. This condition can cause long-term damage or even lead to death if it's not addressed accordingly.

8. Kidney Failure

Kidney disease is relatively common in older dogs and can cause rapid weight loss. The kidneys are organs that can lose efficiency over time. The problem with kidney failure is that the symptoms of this failure often go unnoticed until it starts to cause some major damage.

Keep an eye out on your dog's attitude and overall health. Many of the symptoms of kidney failure are similar to liver failure. You may see things like lethargy, vomiting, and diarrhea.

One distinct symptom, however, is blood in the urine. Seek veterinary care immediately. Luckily, you can often manage the condition with foods that don't put a ton of stress on the kidneys.

9. Heart Disease

It's easy for heart disease to go unnoticed. Many people mistake the symptoms of the disease as simple aging. Truth is, heart disease is very common in senior dogs. The heart begins to lose efficiency. Fluids can build up and your dog may experience a series of other issues as a result.

Symptoms of heart disease include a persistent cough, irregular heartbeat, and restlessness. You may also find that your dog can't exercise for too long without panting excessively.

Your vet can help you manage the condition with some prescription medication. Depending on the severity of the problem, you may also be faced with the tough decision of surgery. Diagnosing the problem early on can decrease the effects.

10. Cancer

Next, there's the condition that no dog owner wants to think about. There are several types of cancer that could affect dogs. Some breeds are more susceptible to others. The problem with cancer is that it can be very difficult for owners to spot.

Some forms of cancer manifest themselves through physical lumps or spots. Others hide under the skin.

If you notice anything strange about your dog's behavior and physical appearance, it's best to err on the side of caution. Getting an early diagnosis can improve prognosis significantly, so don't hesitate to bring your dog to the vet if you notice a lump or other irregularity.

11. Thyroid Issues

The thyroid is responsible for controlling hormones throughout the body. When this vital gland goes out of whack, it can lead to some serious health ramifications. Hyperthyroidism is known to cause sudden weight loss is dogs of all ages. Essentially, the body metabolizes food at a very rapid pace.

As a result, your dog's body can't properly absorb and use the nutrients from their food. The digestive tract processes it quickly, which leads to a sudden drop in weight.

As always, veterinary care is required. Hyperthyroidism can be managed with medication, allowing your dog's body to go back to normal.

12. Addison's Disease

Addison's Disease is another condition that has to do with hormones. It's a rare condition, but it's worth going over. Addison's Disease is most commonly found in Bearded Collies, Poodles, Rottweilers, and a handful of other breeds.

With this condition, the dog's body experiences a significant decrease in steroid hormones. This results in increased blood pressure, diarrhea, vomiting, and weight loss.

Other Possible Solutions

Whether you have a clear idea of what's causing your dog to lose weight or not, it's good to take them to the vet. It's better to be safe than sorry.

Your vet can perform a thorough medical examination and rule out any possible health issues. Once they get a good clean bill of health, you can start looking at other causes and solutions.

Disinterest in Food

Sometimes, weight loss is simply a byproduct of food boredom. If you have a particularly picky pooch, they may not be too fond of their standard kibble anymore.

You'd be surprised how common this is and what lengths dogs will go to send a message. Your dog might start skipping meals or only taking a few bites.

If that's the case, switch things up! Try a premium kibble or simply switch formulas. A different flavor profile can do a lot to get your dog excited. Just make sure that the new food is meeting all their dietary requirements. 

Also, make the transition slowly to avoid stomach upsets. You can also try to incorporate canned food or flavor toppers to enhance the taste.

Related: 15 Possible Reasons Why Your Dog Won’t Eat

Weight Gainers

If all else fails, you can try a weight gainer. Weight gainers are additives that will increase the calorie count to help your dog pack on the pounds. They're a great option if your dog is underweight and is not affected by any major health issues.

Here's a good weight gainer to try out.

Miracle Vet High-Calorie Weight Gainer for Dogs

Miracle Vet High Calorie Weight Gainer for Dogs & Cats - 2,400 Calories. Adds Healthy Weight to Pets Fast. Vet-Approved for All Breeds and Ages. All Natural.

With 150 calories per ounce of liquid, this product form Miracle Vet can do wonders to prevent weight loss. It comes with a simple dropper for easy portioning. Of those 150 calories, about 130 come from fish oil.

This healthy fat is chock-full of fatty acids to improve the circulatory system and keep the skin supple. It's also about 50 percent whey protein, which can help your dog put on healthy weight instead of pure fat.

As an added touch, the additive also has 29 vitamins, minerals, and nutrients.


Sudden weight loss in your senior dog should be taken seriously. Older pups are much more susceptible to major health conditions than their younger counterparts. By taking care of the underlying issue, your dog can get back to their normal self and feel comfortable eating.

Also Read: Best Dog Food for Older – Senior Dogs


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About the author 


Steve is a writer with over 10 years of experience in dog training and nutritiion.

His goal is to educate dog owners about the ins and outs of canine behavior as well as keeping up with the latest scientific research in the field.