--> My dog has diarrhea and is losing weight—help! – Lively Paws My dog has diarrhea and is losing weight—help! – Lively Paws
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My dog has diarrhea and is losing weight—help!

Golden lab sitting in a field

Weight loss and diarrhea in dogs

Diarrhea that causes dog weight loss is not just unpleasant, it's a problem that needs vet attention. This is because diarrhea that causes weight loss can be a sign of another condition that causes a tummy upset as a complication. When another symptom is present, such as vomiting, blood, or weight loss, this moves things up a level from a simple problem to something that needs taking more seriously. Contrast this with simple diarrhea, which is often found in the snack-happy hound who scavenges. Simple diarrhea has various causes usually sorts itself out after a day or two.

Dog diarrhea 101

A normal stool is one that is a formed sausage shape and easily scooped up. This doesn't happen by chance, but depends on how long food takes to pass along the gut. The more quickly it passes along, the less chance there is for water to be reabsorbed—which means a watery stool. If the problem is bad enough, the result is diarrhea.

Thus, diarrhea is a sign that the gut is sick and not able to absorb water as nature intended. This can happen due to food passing through too quickly or because the gut wall is thickened or inflamed. 

Believe it or not (or perhaps you'd rather not know), what the stool looks like and how often the dog poops can give the vet valuable clues as to what's wrong. So if your dog has a stomach upset, don't be bashful about taking photos of the offering for the vet to see first-hand if there is blood or mucus, and how runny the poop is. Also, follow the dog outside to watch proceedings. It's super helpful for the vet to know if the dog is straining, as well as how many times a day they go. 

How does diarrhea cause dog weight loss?

When diarrhea causes dog weight loss, this is a tell-tale sign of two things. First, it suggests the problem lies in the small intestine. Secondly, the problem has been present for some time. Why so?

The gut is a wonderful thing; from the gullet to the stomach, intestine to the rectum, each part is designed for a special task. It works in the same way that a vehicle has a gas tank, fuel pump, and exhaust system. 

It is the job of the small intestine to finish breaking down food into bite-sized chunks (on a molecular level) that can pass across the gut wall and be absorbed into the bloodstream. Anything that interferes with how the small intestine works means the body can't harvest the goodness (and calories) out of food. Looking at it the other way round, if the gut is unhealthy further downstream (in the large intestine), most of the digestion has already taken place and this is not likely to cause a dog weight loss

Examples of problems that can cause small intestinal diarrhea include: 

  • Lack of certain digestive enzymes
  • Bacterial overgrowth: This happens when bacteria necessary for digestion are booted out and replaced by 'bad' bacteria
  • Low cobalamin levels: This B-vitamin is essential to healthy digestion, but levels can be run down over time
  • Inflammatory bowel disease: The inflamed gut wall prevents absorption
  • Food allergies or intolerance
  • Infections or parasites
  • Pancreatitis
  • Problems with another organ that cause gut inflammation or spasm as a complication

What to do if your dog is losing weight

If a dog has diarrhea and loses weight, it's important to visit the vet. This is because the problem is no longer 'simple' and home remedies are unlikely to help. The other side of the coin is that what you do at home could potentially make things worse, rather than better. 

Sensible options to nurse the dog along are to put them on a bland diet. Take them off their regular food (unless advised otherwise by a vet) and offer easy-to-digest morsels such as boiled chicken, turkey, or white fish meat, bulked up with plain carbohydrates such as boiled white rice. These options are gentle on the gut and can give it a chance to heal. 

It is also helpful to feed little and often. Go back to feeding like you did when they were a pup; divide their daily food allowance into four to six smaller meals. This means each meal is gentler on the stomach, giving it less work to do. 

If the dog is already on a bland diet, you may wish to trial a hypoallergenic diet. There are many misunderstandings about hypoallergenic foods, and it's important to know that they are not all equal. The savvy owner reads the label and understands the implications of the ingredients. Ideally, look for a food with as few ingredients as possible (because the more ingredients there are, the more scope there is for it to trigger a food allergy). Do some homework first and write a list of all the different meats the dog has eaten in the past (e.g., chicken, beef, lamb, etc). Then, seek out a food that contains a novel protein source (i.e., one the dog has never eaten before, such as venison, duck, or salmon). 

Another good idea is to mix a dog-friendly probiotic with the food. This gives the gut a head start in booting out the bad bugs and helping the good guys to set up home once again. Be sure to use a dog probiotic rather than your favorite breakfast probiotic drink, since the bugs in a human gut are different to our four-legged friends. 

Oh, and make sure the dog's deworming is up to date. 

With all that said, it is important to visit the vet. Diarrhea that causes a dog weight loss can be hard to clear up and may require prescription medications. Also, do remember that diarrhea is just a symptom, and not a diagnosis in it's own right. This means the vet may need to run tests to check out things like liver or pancreatic function and seek out a problem for which the diarrhea is the symptom. The good news is that treating this problem should stop the dog weight loss.


Read more about diarrhea in dogs

The article was written by  Pippa Elliot, BVMS, MRCVS on October 30, 2020.

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