Get

In Your Inbox

Dogster is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

What Causes Weight Loss & Diarrhea in Senior Dogs? Vet Explained Health Facts

Share

sick goldendoodle dog lying on a carpet

Nobody likes dealing with diarrhea, especially when it’s plaguing your aging canine companion. But what can be even more concerning is if your senior dog also starts losing weight. In combination, weight loss and diarrhea in a senior dog can have various causes, many of which can be serious. These include inflammatory bowel disease, pancreatic insufficiency, food allergies, an infection, or even cancer.

We delve into this topic here to help you find the reason for your dog’s weight loss and diarrhea so your pup can better enjoy their golden years.

divider dog paws 2 oct 2024

The 8 Common Causes of Weight Loss and Diarrhea in Senior Dogs

There are many possible causes of weight loss and diarrhea in dogs. Keep in mind that this list just scratches the surface of possibilities, so be sure to seek veterinary attention for a proper diagnosis.

Speak to a veterinarian so you can rule out any serious health conditions and get advice on what approach might be best to help your dog.

If you need to speak with a vet but can't get to one, head over to PangoVet. It's our online service where you can talk to a vet online and get the advice you need for your pet — all at an affordable price!

PangoVet_Mention-in-Content Savings V1

1. Inflammatory bowel disease

This is when the intestines become so inflamed that they have a hard time absorbing nutrients. What you get is chronic diarrhea that can lead to weight loss over time because the dog simply can’t absorb the required nutrients.


2. Exocrine pancreatic insufficiency

The pancreas is a major player in the production of digestive enzymes to help break down food. Sometimes, as a dog ages, pancreatic cells can shrink or become damaged by chronic pancreatitis, causing them to decrease production. What happens next is that digesta can pass through the system without being fully broken down and absorbed. Chronic diarrhea and weight loss can then ensue.


3. Chronic pancreatitis

We can relate exocrine pancreatic insufficiency to pancreatitis, which is when the pancreas becomes inflamed. One case of pancreatitis can cause diarrhea but is unlikely to lead to weight loss. However, if this happens repeatedly over time, it can damage the pancreatic cells so they no longer produce digestive enzymes. Be aware that dogs that experience one case of pancreatitis may be more prone to future cases.


4. Food allergies/intolerances

Dogs can develop allergies to food ingredients that they have eaten without trouble for many years. When this happens, their digestive system has a reaction to the food that can lead to diarrhea, vomiting, and stomach pain. If they continue to eat the food with these issues, it can lead to weight loss.

You are free to use this image but we do require you to link back to Dogster.com for credit

5. Digestive imbalance

A dog’s gut is a wonderful concoction of good bacteria, called the microbiome, that aid in digestion, immune function, and absorption of nutrients. If that balance gets out of whack due to diet, an infection, or medications, it can result in diarrhea and over time, weight loss.


6. Infections/parasites

Many germs and worms can affect a dog’s digestive system, more so in senior dogs that have decreased immune function. Any bacterial, viral, or parasitic infection can result in a disruption to digestion that can bring on diarrhea and weight loss.


7. Cancer

Many types of cancer can lead to weight loss and diarrhea in senior dogs.


8. Other organ issues

The health of a dog’s digestive system is in the hands of many organs, not just the stomach and intestines. Pancreatic issues can cause diarrhea and weight loss, and so can liver and kidney diseases and diabetes, to name a few.

beagle dog sick sad on bed
Image Credit: Iryna Imago, Shutterstock

What to Do for a Senior Dog With Weight Loss and Diarrhea

The previous list can give you an idea of the variation in causes of weight loss and diarrhea in senior dogs. Nearly any issue from the mouth to the anus can lead to these signs, so you’ll want to see a veterinarian to help you on this diagnostic journey.

Expect your vet to run blood work, a fecal sample, and potentially, X-rays, and ask you questions about what you’re feeding your dog, their appetite, and any other signs that you’ve noticed.

From there, your vet can recommend a treatment plan aimed at the underlying disease. This may include a diet change, deworming, antibiotics, enzyme supplements, surgery, or probiotics. Don’t take a wait-and-see approach for a dog with weight loss and diarrhea. The sooner you can treat your pet, the better.

How Do You Know If Your Senior Dog Is Suffering?

Diarrhea and weight loss are two things that definitely don’t boost a dog’s quality of life, but most of their causes are fixable. See your veterinarian to determine the reason for your dog’s weight loss and diarrhea, and follow any treatment plan that they recommend.

Some causes will need lifelong management, which may include a diet change or medication that needs to be given with every meal. Others can be cleared up with one round of antibiotics, probiotics, or a dewormer.

Then, there are certain cases that can’t be cured, such as specific types of cancer. In these situations, it’s best to work closely with your veterinarian to determine the best course of action to keep your pup as comfortable and as happy as possible. You’ll want to watch for signs like inappetence, lethargy, or severe discomfort to determine if your dog is suffering.

divider dog paws oct 2024

Conclusion

Aging presents a unique set of challenges for our canine companions, including weight loss and diarrhea. Your dog will need your and your veterinarian’s help to determine the cause and best course of treatment so they can live out their golden years in the best way possible.


Featured Image Credit: Brad K Covington, Shutterstock

Want content like this delivered to you?

Sign Up For Our Newsletter

News, insights, expert advice, and everything dog

* By submitting, you agree to our Terms & Conditions and Privacy & Cookies Policy.




How useful was this post?

Click on a star to rate (you can leave written feedback after clicking submit)

Help us improve Dogster for pet parents!

Your feedback really matters.

What did you like about this post? Also how can we improve it?

Join the conversation

Leave a Reply

You’re very welcome to leave a comment or question. Please know that all comments must meet our community guidelines, and your email address will NOT be published. Let’s have a positive and constructive conversation.


Talk With A Vet Online

Peace of mind,
anywhere, anytime

Affordable vet advice

From Fighting Ring to Cuddle Monster: Eli and the Importance of Fostering

We all know the importance of adopting pets from animal shelters, and how choosing to bring home a dog from a pet rescue...

Ask Dr. Paola- Help! My Dogs Are Overweight! (April 13, 2026)

Welcome to our “Ask Dr. Paola” series, where every Monday we bring expert advice straight from Dr. Paola Cuevas (MVZ) to help our...

Dogster’s Weekly Photo Contest Winners: Best Easter Photo (April 9, 2026)

Every week our team gets the privilege of sorting through our readers photos to choose what dogs will win this weeks contest! See...

We Didn’t Just Add a Dog to Our Life – We Built a Life With Him

“We didn’t just bring a dog home—we built a life together.” Most people are quietly taught a version of pet ownership that looks...

More related

Cavalier King Charles Spaniel vs. King Charles Spaniel: The Differences (With Pictures)

You may have heard of the Cavalier King Charles Spaniel and the King Charles Spaniel, also called the English Toy Spaniel, and wondered...

Are Dogs Allowed at Crater Lake? (Updated in 2026)

Known for its purity and crystal blue water, Crater Lake is the deepest lake in the U.S.A. It was formed 7,700 years ago...

Great Pyrenees vs Golden Retriever: Key Diffenences Explained (With Pictures)

Selecting the ideal dog for your home can be challenging, but it’s easier when you’ve narrowed down your choices. If you love gentle,...

Goughnuts Dog Toy Review 2026: Is It a Good Value? An Expert’s Breakdown

What Is Goughnuts? How Does It Work? Goughnuts is a dog toy company that focuses on durable chew toys. Goughnuts is an American...

Keep reading

8 Best Puppy Foods for Medium Breeds in 2026 – Reviews & Top Picks

Shopping for the right food for your new puppy can be a bit overwhelming. Any dog lover knows that the food choices on the market today are seemingly endless. Even if you’re a brand-new dog owner, all you have to...

cocker spaniel in grass field

9 Dog Food Games to Play to Make Mealtime Fun for Your Pup

Our canine companions require a lot of enrichment and a good variety of it. Including exercise and playtime in their daily lives is easy, but how can you enrich their mealtimes? Meals can always be made more fun and exciting...

Dog playing shell game with her human

10 Best Dry Dog Foods in Canada in 2026: Reviews & Top Picks

Feeding your dog is one of the top priorities for all dog owners, and finding the perfect dog food that will keep your pup happy and in good health is essential! But whether you’re looking to switch your dog’s food...

labrador dog eating food indoor

What Berries Can Dogs Eat? Vet-Verified Nutrition Facts & FAQ

Can dogs eat berries? Well, there’s no simple answer to this seemingly simple question. There are over 400 different types of known berries, and some are safe for dogs to eat, while others are only safe for human consumption. Some...

cluster of elderberry fruit

Is There Beer for Dogs? Vet-Verified Types, Info & FAQ

When we go to restaurants, we’re usually given multiple drink options, while dogs are typically served water. However, many dog-friendly bars and restaurants have gotten creative over the years and have added beer for dogs to their menus. You don’t...

dog owner beer

Can Dogs Eat Vanilla Wafers? Vet-Reviewed Facts & FAQ

Vanilla wafers are not toxic to dogs, although they certainly aren’t the healthiest. Therefore, they aren’t a good option as a treat or snack. If your dog accidentally eats a vanilla wafer, there isn’t much to be concerned about, though....

Can Dogs Eat_vanilla wafers

Can Dogs Eat Sour Patch Kids? Keep Your Dog Healthy!

If your dog begs for any food you put in your mouth, it probably won’t stop just because you’re eating something unsafe for them. That’s why it’s important to know which human snacks dogs can eat. Sour Patch Kids candy...

Can Dogs Eat_patch kids

5 Easy Dog-Friendly Recipes You Can Try at Home

It’s so easy to make your dog one of these five dog-friendly recipes: The Top 5 Dog-Friendly Recipes 1. Turkey-Rice Casserole This recipe makes a great everyday meal, especially with the addition of homemade gravy. Ingredients: Directions: In a large...

Dog-Friendly Recipes You Can Try at Home

Love Dogs? So Do We! Join the Dogster Community

Stay informed with expert pet care insights delivered straight to your inbox! Discover professional guidance on animal behavior, feeding tips, trusted product picks, and much more.




Sign up for the Dogster Email Newsletter